Handbuch für Software-Entwickler für die Intel 64 und IA-32-Architektur, Band 3 B: Handbuch der Systemprogrammierung (Teil 2)

Handbuch für Software-Entwickler für die Intel 64 und IA-32-Architektur, Band 3 B: Handbuch der Systemprogrammierung (Teil 2)
Intel® 64 and IA-32 Architectures
Software Developer’s Manual
Volume 3B:
System Programming Guide, Part 2
NOTE: The Intel® 64 and IA-32 Architectures Software Developer's Manual consists of eight volumes:
Basic Architecture, Order Number 253665; Instruction Set Reference A-M, Order Number 253666;
Instruction Set Reference N-Z, Order Number 253667; Instruction Set Reference, Order Number
326018; System Programming Guide, Part 1, Order Number 253668; System Programming Guide, Part
2, Order Number 253669; System Programming Guide, Part 3, Order Number 326019; System
Programming Guide, Part 4, Order Number 332831. Refer to all eight volumes when evaluating your
design needs.
Order Number: 253669-058US
April 2016
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CHAPTER 14
POWER AND THERMAL MANAGEMENT
This chapter describes facilities of Intel 64 and IA-32 architecture used for power management and thermal monitoring.
14.1
ENHANCED INTEL SPEEDSTEP® TECHNOLOGY
Enhanced Intel SpeedStep® Technology was introduced in the Pentium M processor. The technology enables the
management of processor power consumption via performance state transitions. These states are defined as
discrete operating points associated with different voltages and frequencies.
Enhanced Intel SpeedStep Technology differs from previous generations of Intel SpeedStep Technology in two
ways:
•
Centralization of the control mechanism and software interface in the processor by using model-specific
registers.
•
Reduced hardware overhead; this permits more frequent performance state transitions.
Previous generations of the Intel SpeedStep Technology require processors to be a deep sleep state, holding off bus
master transfers for the duration of a performance state transition. Performance state transitions under the
Enhanced Intel SpeedStep Technology are discrete transitions to a new target frequency.
Support is indicated by CPUID, using ECX feature bit 07. Enhanced Intel SpeedStep Technology is enabled by
setting IA32_MISC_ENABLE MSR, bit 16. On reset, bit 16 of IA32_MISC_ENABLE MSR is cleared.
14.1.1
Software Interface For Initiating Performance State Transitions
State transitions are initiated by writing a 16-bit value to the IA32_PERF_CTL register, see Figure 14-2. If a transition is already in progress, transition to a new value will subsequently take effect.
Reads of IA32_PERF_CTL determine the last targeted operating point. The current operating point can be read from
IA32_PERF_STATUS. IA32_PERF_STATUS is updated dynamically.
The 16-bit encoding that defines valid operating points is model-specific. Applications and performance tools are
not expected to use either IA32_PERF_CTL or IA32_PERF_STATUS and should treat both as reserved. Performance
monitoring tools can access model-specific events and report the occurrences of state transitions.
14.2
P-STATE HARDWARE COORDINATION
The Advanced Configuration and Power Interface (ACPI) defines performance states (P-states) that are used to
facilitate system software’s ability to manage processor power consumption. Different P-states correspond to
different performance levels that are applied while the processor is actively executing instructions. Enhanced Intel
SpeedStep Technology supports P-states by providing software interfaces that control the operating frequency and
voltage of a processor.
With multiple processor cores residing in the same physical package, hardware dependencies may exist for a
subset of logical processors on a platform. These dependencies may impose requirements that impact the coordination of P-state transitions. As a result, multi-core processors may require an OS to provide additional software
support for coordinating P-state transitions for those subsets of logical processors.
ACPI firmware can choose to expose P-states as dependent and hardware-coordinated to OS power management
(OSPM) policy. To support OSPMs, multi-core processors must have additional built-in support for P-state hardware
coordination and feedback.
Intel 64 and IA-32 processors with dependent P-states amongst a subset of logical processors permit hardware
coordination of P-states and provide a hardware-coordination feedback mechanism using IA32_MPERF MSR and
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IA32_APERF MSR. See Figure 14-1 for an overview of the two 64-bit MSRs and the bullets below for a detailed
description:
63
0
IA32_MPERF (Addr: E7H)
63
0
IA32_APERF (Addr: E8H)
Figure 14-1. IA32_MPERF MSR and IA32_APERF MSR for P-state Coordination
•
Use CPUID to check the P-State hardware coordination feedback capability bit. CPUID.06H.ECX[Bit 0] = 1
indicates IA32_MPERF MSR and IA32_APERF MSR are present.
•
IA32_MPERF MSR (E7H) increments in proportion to a fixed frequency, which is configured when the processor
is booted.
•
IA32_APERF MSR (E8H) increments in proportion to actual performance, while accounting for hardware coordination of P-state and TM1/TM2; or software initiated throttling.
•
The MSRs are per logical processor; they measure performance only when the targeted processor is in the C0
state.
•
Only the IA32_APERF/IA32_MPERF ratio is architecturally defined; software should not attach meaning to the
content of the individual of IA32_APERF or IA32_MPERF MSRs.
•
•
When either MSR overflows, both MSRs are reset to zero and continue to increment.
Both MSRs are full 64-bits counters. Each MSR can be written to independently. However, software should
follow the guidelines illustrated in Example 14-1.
If P-states are exposed by the BIOS as hardware coordinated, software is expected to confirm processor support
for P-state hardware coordination feedback and use the feedback mechanism to make P-state decisions. The OSPM
is expected to either save away the current MSR values (for determination of the delta of the counter ratio at a later
time) or reset both MSRs (execute WRMSR with 0 to these MSRs individually) at the start of the time window used
for making the P-state decision. When not resetting the values, overflow of the MSRs can be detected by checking
whether the new values read are less than the previously saved values.
Example 14-1 demonstrates steps for using the hardware feedback mechanism provided by IA32_APERF MSR and
IA32_MPERF MSR to determine a target P-state.
Example 14-1. Determine Target P-state From Hardware Coordinated Feedback
DWORD PercentBusy; // Percentage of processor time not idle.
// Measure “PercentBusy“ during previous sampling window.
// Typically, “PercentBusy“ is measure over a time scale suitable for
// power management decisions
//
// RDMSR of MCNT and ACNT should be performed without delay.
// Software needs to exercise care to avoid delays between
// the two RDMSRs (for example, interrupts).
MCNT = RDMSR(IA32_MPERF);
ACNT = RDMSR(IA32_APERF);
// PercentPerformance indicates the percentage of the processor
// that is in use. The calculation is based on the PercentBusy,
// that is the percentage of processor time not idle and the P-state
// hardware coordinated feedback using the ACNT/MCNT ratio.
// Note that both values need to be calculated over the same
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POWER AND THERMAL MANAGEMENT
// time window.
PercentPerformance = PercentBusy * (ACNT/MCNT);
// This example does not cover the additional logic or algorithms
// necessary to coordinate multiple logical processors to a target P-state.
TargetPstate = FindPstate(PercentPerformance);
if (TargetPstate ≠ currentPstate) {
SetPState(TargetPstate);
}
// WRMSR of MCNT and ACNT should be performed without delay.
// Software needs to exercise care to avoid delays between
// the two WRMSRs (for example, interrupts).
WRMSR(IA32_MPERF, 0);
WRMSR(IA32_APERF, 0);
14.3
SYSTEM SOFTWARE CONSIDERATIONS AND OPPORTUNISTIC PROCESSOR
PERFORMANCE OPERATION
An Intel 64 processor may support a form of processor operation that takes advantage of design headroom to
opportunistically increase performance. The Intel Turbo Boost Technology can convert thermal headroom into
higher performance across multi-threaded and single-threaded workloads. The Intel Dynamic Acceleration feature
can convert thermal headroom into higher performance if only one thread is active.
14.3.1
Intel Dynamic Acceleration
Intel Core 2 Duo processor T 7700 introduces Intel Dynamic Acceleration (IDA). IDA takes advantage of thermal
design headroom and opportunistically allows a single core to operate at a higher performance level when the
operating system requests increased performance.
14.3.2
System Software Interfaces for Opportunistic Processor Performance Operation
Opportunistic processor operation, applicable to Intel Dynamic Acceleration and Intel Turbo Boost Technology, has
the following characteristics:
•
A transition from a normal state of operation (e.g. IDA/Turbo mode disengaged) to a target state is not
guaranteed, but may occur opportunistically after the corresponding enable mechanism is activated, the
headroom is available and certain criteria are met.
•
•
The opportunistic processor performance operation is generally transparent to most application software.
•
When opportunistic processor performance operation is engaged, the OS should use hardware coordination
feedback mechanisms to prevent un-intended policy effects if it is activated during inappropriate situations.
System software (BIOS and Operating system) must be aware of hardware support for opportunistic processor
performance operation and may need to temporarily disengage opportunistic processor performance operation
when it requires more predictable processor operation.
14.3.2.1
Discover Hardware Support and Enabling of Opportunistic Processor Operation
If an Intel 64 processor has hardware support for opportunistic processor performance operation, the power-on
default state of IA32_MISC_ENABLE[38] indicates the presence of such hardware support. For Intel 64 processors
that support opportunistic processor performance operation, the default value is 1, indicating its presence. For
processors that do not support opportunistic processor performance operation, the default value is 0. The powerVol. 3B 14-3
POWER AND THERMAL MANAGEMENT
on default value of IA32_MISC_ENABLE[38] allows BIOS to detect the presence of hardware support of opportunistic processor performance operation.
IA32_MISC_ENABLE[38] is shared across all logical processors in a physical package. It is written by BIOS during
platform initiation to enable/disable opportunistic processor operation in conjunction of OS power management
capabilities, see Section 14.3.2.2. BIOS can set IA32_MISC_ENABLE[38] with 1 to disable opportunistic processor
performance operation; it must clear the default value of IA32_MISC_ENABLE[38] to 0 to enable opportunistic
processor performance operation. OS and applications must use CPUID leaf 06H if it needs to detect processors
that has opportunistic processor operation enabled.
When CPUID is executed with EAX = 06H on input, Bit 1 of EAX in Leaf 06H (i.e. CPUID.06H:EAX[1]) indicates
opportunistic processor performance operation, such as IDA, has been enabled by BIOS.
Opportunistic processor performance operation can be disabled by setting bit 38 of IA32_MISC_ENABLE. This
mechanism is intended for BIOS only. If IA32_MISC_ENABLE[38] is set, CPUID.06H:EAX[1] will return 0.
14.3.2.2
OS Control of Opportunistic Processor Performance Operation
There may be phases of software execution in which system software cannot tolerate the non-deterministic aspects
of opportunistic processor performance operation. For example, when calibrating a real-time workload to make a
CPU reservation request to the OS, it may be undesirable to allow the possibility of the processor delivering
increased performance that cannot be sustained after the calibration phase.
System software can temporarily disengage opportunistic processor performance operation by setting bit 32 of the
IA32_PERF_CTL MSR (0199H), using a read-modify-write sequence on the MSR. The opportunistic processor
performance operation can be re-engaged by clearing bit 32 in IA32_PERF_CTL MSR, using a read-modify-write
sequence. The DISENAGE bit in IA32_PERF_CTL is not reflected in bit 32 of the IA32_PERF_STATUS MSR (0198H),
and it is not shared between logical processors in a physical package. In order for OS to engage IDA/Turbo mode,
the BIOS must
•
•
enable opportunistic processor performance operation, as described in Section 14.3.2.1,
expose the operating points associated with IDA/Turbo mode to the OS.
33 32 31
63
16 15
0
Reserved
IDA/Turbo DISENGAGE
Enhanced Intel Speedstep Technology Transition Target
Figure 14-2. IA32_PERF_CTL Register
14.3.2.3
Required Changes to OS Power Management P-state Policy
Intel Dynamic Acceleration (IDA) and Intel Turbo Boost Technology can provide opportunistic performance greater
than the performance level corresponding to the Processor Base frequency of the processor (see CPUID’s processor
frequency information). System software can use a pair of MSRs to observe performance feedback. Software must
query for the presence of IA32_APERF and IA32_MPERF (see Section 14.2). The ratio between IA32_APERF and
IA32_MPERF is architecturally defined and a value greater than unity indicates performance increase occurred
during the observation period due to IDA. Without incorporating such performance feedback, the target P-state
evaluation algorithm can result in a non-optimal P-state target.
There are other scenarios under which OS power management may want to disable IDA, some of these are listed
below:
•
When engaging ACPI defined passive thermal management, it may be more effective to disable IDA for the
duration of passive thermal management.
14-4 Vol. 3B
POWER AND THERMAL MANAGEMENT
•
When the user has indicated a policy preference of power savings over performance, OS power management
may want to disable IDA while that policy is in effect.
14.3.3
Intel Turbo Boost Technology
Intel Turbo Boost Technology is supported in Intel Core i7 processors and Intel Xeon processors based on Intel®
microarchitecture code name Nehalem. It uses the same principle of leveraging thermal headroom to dynamically
increase processor performance for single-threaded and multi-threaded/multi-tasking environment. The programming interface described in Section 14.3.2 also applies to Intel Turbo Boost Technology.
14.3.4
Performance and Energy Bias Hint support
Intel 64 processors may support additional software hint to guide the hardware heuristic of power management
features to favor increasing dynamic performance or conserve energy consumption.
Software can detect the processor's capability to support the performance-energy bias preference hint by examining bit 3 of ECX in CPUID leaf 6. The processor supports this capability if CPUID.06H:ECX.SETBH[bit 3] is set and
it also implies the presence of a new architectural MSR called IA32_ENERGY_PERF_BIAS (1B0H).
Software can program the lowest four bits of IA32_ENERGY_PERF_BIAS MSR with a value from 0 - 15. The values
represent a sliding scale, where a value of 0 (the default reset value) corresponds to a hint preference for highest
performance and a value of 15 corresponds to the maximum energy savings. A value of 7 roughly translates into a
hint to balance performance with energy consumption.
4 3
63
0
Reserved
Energy Policy Preference Hint
Figure 14-3. IA32_ENERGY_PERF_BIAS Register
The layout of IA32_ENERGY_PERF_BIAS is shown in Figure 14-3. The scope of IA32_ENERGY_PERF_BIAS is per
logical processor, which means that each of the logical processors in the package can be programmed with a
different value. This may be especially important in virtualization scenarios, where the performance / energy
requirements of one logical processor may differ from the other. Conflicting “hints” from various logical processors
at higher hierarchy level will be resolved in favor of performance over energy savings.
Software can use whatever criteria it sees fit to program the MSR with an appropriate value. However, the value
only serves as a hint to the hardware and the actual impact on performance and energy savings is model specific.
14.4
HARDWARE-CONTROLLED PERFORMANCE STATES (HWP)
Intel processors may contain support for Hardware-Controlled Performance States (HWP), which autonomously
selects performance states while utilizing OS supplied performance guidance hints. The Enhanced Intel SpeedStep® Technology provides a means for the OS to control and monitor discrete frequency-based operating points
via the IA32_PERF_CTL and IA32_PERF_STATUS MSRs.
In contrast, HWP is an implementation of the ACPI-defined Collaborative Processor Performance Control (CPPC),
which specifies that the platform enumerate a continuous, abstract unit-less, performance value scale that is not
tied to a specific performance state / frequency by definition. While the enumerated scale is roughly linear in terms
of a delivered integer workload performance result, the OS is required to characterize the performance value range
to comprehend the delivered performance for an applied workload.
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POWER AND THERMAL MANAGEMENT
When HWP is enabled, the processor autonomously selects performance states as deemed appropriate for the
applied workload and with consideration of constraining hints that are programmed by the OS. These OS-provided
hints include minimum and maximum performance limits, preference towards energy efficiency or performance,
and the specification of a relevant workload history observation time window. The means for the OS to override
HWP's autonomous selection of performance state with a specific desired performance target is also provided,
however, the effective frequency delivered is subject to the result of energy efficiency and performance optimizations.
14.4.1
HWP Programming Interfaces
The programming interfaces provided by HWP include the following:
•
The CPUID instruction allows software to discover the presence of HWP support in an Intel processor. Specifically, execute CPUID instruction with EAX=06H as input will return 5 bit flags covering the following aspects in
bits 7 through 11 of CPUID.06H:EAX:
— Availability of HWP baseline resource and capability, CPUID.06H:EAX[bit 7]: If this bit is set, HWP provides
several new architectural MSRs: IA32_PM_ENABLE, IA32_HWP_CAPABILITIES, IA32_HWP_REQUEST,
IA32_HWP_STATUS.
— Availability of HWP Notification upon dynamic Guaranteed Performance change, CPUID.06H:EAX[bit 8]: If
this bit is set, HWP provides IA32_HWP_INTERRUPT MSR to enable interrupt generation due to dynamic
Performance changes and excursions.
— Availability of HWP Activity window control, CPUID.06H:EAX[bit 9]: If this bit is set, HWP allows software to
program activity window in the IA32_HWP_REQUEST MSR.
— Availability of HWP energy/performance preference control, CPUID.06H:EAX[bit 10]: If this bit is set, HWP
allows software to set an energy/performance preference hint in the IA32_HWP_REQUEST MSR.
— Availability of HWP package level control, CPUID.06H:EAX[bit 11]:If this bit is set, HWP provides the
IA32_HWP_REQUEST_PKG MSR to convey OS Power Management’s control hints for all logical processors
in the physical package.
Table 14-1. Architectural and Non-Architectural MSRs Related to HWP
•
Address
Archite
ctural
Register Name
Description
770H
Y
IA32_PM_ENABLE
771H
Y
IA32_HWP_CAPABILITIES
Enumerates the HWP performance range (static and dynamic).
772H
Y
IA32_HWP_REQUEST_PKG
Conveys OSPM's control hints (Min, Max, Activity Window, Energy
Performance Preference, Desired) for all logical processor in the physical
package.
773H
Y
IA32_HWP_INTERRUPT
774H
Y
IA32_HWP_REQUEST
777H
Y
IA32_HWP_STATUS
19CH
Y
IA32_THERM_STATUS[bits 15:12]
64EH
N
MSR_PPERF
Enable/Disable HWP.
Controls HWP native interrupt generation (Guaranteed Performance
changes, excursions).
Conveys OSPM's control hints (Min, Max, Activity Window, Energy
Performance Preference, Desired) for a single logical processor.
Status bits indicating changes to Guaranteed Performance and
excursions to Minimum Performance.
Conveys reasons for performance excursions
Productive Performance Count.
Additionally, HWP may provide a non-architectural MSR, MSR_PPERF, which provides a quantitative metric to
software of hardware’s view of workload scalability. This hardware’s view of workload scalability is implementation specific.
14-6 Vol. 3B
POWER AND THERMAL MANAGEMENT
14.4.2
Enabling HWP
The layout of the IA32_PM_ENABLE MSR is shown in Figure 14-4. The bit fields are described below:
63
1 0
Reserved
HWP_ENABLE
Reserved
Figure 14-4. IA32_PM_ENABLE MSR
•
HWP_ENABLE (bit 0, R/W1Once) — Software sets this bit to enable HWP with autonomous selection. When
set, the processor will disregard input from the legacy performance control interface (IA32_PERF_CTL). Note
this bit can only be enabled once from the default value. Once set, writes to the HWP_ENABLE bit are ignored.
Only RESET will clear this bit. Default = zero (0).
•
Bits 63:1 are reserved and must be zero.
After software queries CPUID and verifies the processor’s support of HWP, system software can write 1 to
IA32_PM_ENABLE.HWP_ENABLE (bit 0) to enable hardware controlled performance states. The default value of
IA32_PM_ENABLE MSR at power-on is 0, i.e. HWP is disabled.
Additional MSRs associated with HWP may only be accessed after HWP is enabled, with the exception of
IA32_HWP_INTERRUPT and MSR_PPERF. Accessing the IA32_HWP_INTERRUPT MSR requires only HWP is present
as enumerated by CPUID but does not require enabling HWP.
IA32_PM_ENABLE is a package level MSR, i.e. writing to it from any logical processor within a package affects all
logical processors within that package.
14.4.3
HWP Performance Range and Dynamic Capabilities
The OS reads the IA32_HWP_CAPABILITIES MSR to comprehend the limits of the HWP-managed performance
range as well as the dynamic capability, which may change during processor operation. The enumerated performance range values reported by IA32_HWP_CAPABILITIES directly map to initial frequency targets (prior to workload-specific frequency optimizations of HWP). However the mapping is processor family specific.
The layout of the IA32_HWP_CAPABILITIES MSR is shown in Figure 14-5. The bit fields are described below:
63
32 31
24 23
16 15
8
7
0
Reserved
Lowest_Performance
Most_Efficient_Performance
Guaranteed_Performance
Highest_Performance
Figure 14-5. IA32_HWP_CAPABILITIES Register
•
•
Highest_Performance (bits 7:0, RO) — Value for the maximum non-guaranteed performance level.
•
Most_Efficient_Performance (bits 23:16, RO) — Current value of the most efficient performance level.
This value can change dynamically as a result of workload characteristics.
Guaranteed_Performance (bits 15:8, RO) — Current value for the guaranteed performance level. This
value can change dynamically as a result of internal or external constraints, e.g. thermal or power limits.
Vol. 3B 14-7
POWER AND THERMAL MANAGEMENT
•
Lowest_Performance (bits 31:24, RO) — Value for the lowest performance level that software can program
to IA32_HWP_REQUEST.
•
Bits 63:32 are reserved and must be zero.
The value returned in the Guaranteed_Performance field is hardware's best-effort approximation of the available performance given current operating constraints. Changes to the Guaranteed_Performance value will
primarily occur due to a shift in operational mode. This includes a power or other limit applied by an external agent,
e.g. RAPL (see Figure 14.9.1), or the setting of a Configurable TDP level (see model-specific controls related to
Programmable TDP Limit in Chapter 35, “Model-Specific Registers (MSRs)”). Notification of a change to the
Guaranteed_Performance occurs via interrupt (if configured) and the IA32_HWP_Status MSR. Changes to
Guaranteed_Performance are indicated when a macroscopically meaningful change in performance occurs i.e.
sustained for greater than one second. Consequently, notification of a change in Guaranteed Performance will typically occur no more frequently than once per second. Rapid changes in platform configuration, e.g. docking /
undocking, with corresponding changes to a Configurable TDP level could potentially cause more frequent notifications.
The value returned by the Most_Efficient_Performance field provides the OS with an indication of the practical
lower limit for the IA32_HWP_REQUEST. The processor may not honor IA32_HWP_REQUEST.Maximum Performance settings below this value.
14.4.4
Managing HWP
Typically, the OS controls HWP operation for each logical processor via the writing of control hints / constraints to
the IA32_HWP_REQUEST MSR. The layout of the IA32_HWP_REQUEST MSR is shown in Figure 14-6. The bit fields
are described below:
63
43 42 41
32 31
24 23
16 15
8
7
0
Reserved
Package_Control
Activity_Window
Energy_Performance_Preference
Desired_Performance
Maximum_Performance
Minimum_Performance
Figure 14-6. IA32_HWP_REQUEST Register
•
Minimum_Performance (bits 7:0, RW) — Conveys a hint to the HWP hardware. The OS programs the
minimum performance hint to achieve the required quality of service (QOS) or to meet a service level
agreement (SLA) as needed. Note that an excursion below the level specified is possible due to hardware
constraints. The default value of this field is IA32_HWP_CAPABILITIES.Lowest_Performance.
•
Maximum_Performance (bits 15:8, RW) — Conveys a hint to the HWP hardware. The OS programs this
field to limit the maximum performance that is expected to be supplied by the HWP hardware. Excursions
above the limit requested by OS are possible due to hardware coordination between the processor cores and
other components in the package. The default value of this field is
IA32_HWP_CAPABILITIES.Highest_Performance.
•
Desired_Performance (bits 23:16, RW) — Conveys a hint to the HWP hardware. When set to zero,
hardware autonomous selection determines the performance target. When set to a non-zero value (between
the range of Lowest_Performance and Highest_Performance of IA32_HWP_CAPABILITIES) conveys an explicit
performance request hint to the hardware; effectively disabling HW Autonomous selection. The
Desired_Performance input is non-constraining in terms of Performance and Energy Efficiency optimizations,
which are independently controlled. The default value of this field is 0.
•
Energy_Performance_Preference (bits 31:24, RW) — Conveys a hint to the HWP hardware. The OS may
write a range of values from 0 (performance preference) to 0FFH (energy efficiency preference) to influence the
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POWER AND THERMAL MANAGEMENT
rate of performance increase /decrease and the result of the hardware's energy efficiency and performance
optimizations. The default value of this field is 80H. Note: If CPUID.06H:EAX[bit 10] indicates that this field is
not supported, HWP uses the value of the IA32_ENERGY_PERF_BIAS MSR to determine the energy efficiency /
performance preference.
•
Activity_Window (bits 41:32, RW) — Conveys a hint to the HWP hardware specifying a moving workload
history observation window for performance/frequency optimizations. If 0, the hardware will determine the
appropriate window size. When writing a non-zero value to this field, this field is encoded in the format of bits
38:32 as a 7-bit mantissa and bits 41:39 as a 3-bit exponent value in powers of 10. The resultant value is in
microseconds. Thus, the minimal/maximum activity window size is 1 microsecond/1270 seconds. Combined
with the Energy_Performance_Preference input, Activity_Window influences the rate of performance increase
/ decrease. This non-zero hint only has meaning when Desired_Performance = 0. The default value of this field
is 0.
•
Package_Control (bit 42, RW) — When set causes this logical processor's IA32_HWP_REQUEST control
inputs to be derived from IA32_HWP_REQUEST_PKG
•
Bits 63:43 are reserved and must be zero.
The HWP hardware clips and resolves the field values as necessary to the valid range. Reads return the last value
written not the clipped values.
Processors may support a subset of IA32_HWP_REQUEST fields as indicated by CPUID. Reads of non-supported
fields will return 0. Writes to non-supported fields are ignored.
The OS may override HWP's autonomous selection of performance state with a specific performance target by
setting the Desired_Performance field to a non zero value, however, the effective frequency delivered is subject to
the result of energy efficiency and performance optimizations, which are influenced by the Energy Performance
Preference field.
Software may disable all hardware optimizations by setting Minimum_Performance = Maximum_Performance
(subject to package coordination).
Note: The processor may run below the Minimum_Performance level due to hardware constraints including: power,
thermal, and package coordination constraints. The processor may also run below the Minimum_Performance level
for short durations (few milliseconds) following C-state exit, and when Hardware Duty Cycling (see Section 14.5)
is enabled.
63
42 41
32 31
24 23
16 15
8
7
0
Reserved
Activity_Window
Energy_Performance_Preference
Desired_Performance
Maximum_Performance
Minimum_Performance
Figure 14-7. IA32_HWP_REQUEST_PKG Register
The structure of the IA32_HWP_REQUEST_PKG MSR (package-level) is identical to the IA32_HWP_REQUEST MSR
with the exception of the Package Control field, which does not exist. Field values written to this MSR apply to all
logical processors within the physical package with the exception of logical processors whose
IA32_HWP_REQUEST.Package Control field is clear (zero). Single P-state Control mode is only supported when
IA32_HWP_REQUEST_PKG is not supported.
14.4.5
HWP Feedback
The processor provides several types of feedback to the OS during HWP operation.
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POWER AND THERMAL MANAGEMENT
The IA32_MPERF MSR and IA32_APERF MSR mechanism (see Section 14.2) allows the OS to calculate the resultant
effective frequency delivered over a time period. Energy efficiency and performance optimizations directly impact
the resultant effective frequency delivered.
The layout of the IA32_HWP_STATUS MSR is shown in Figure 14-8. It provides feedback regarding changes to
IA32_HWP_CAPABILITIES.Guaranteed_Performance and excursions to
IA32_HWP_CAPABILITIES.Minimum_Performance. The bit fields are described below:
•
Guaranteed_Performance_Change (bit 0, RWC0) — If set (1), a change to Guaranteed_Performance has
occurred. Software should query IA32_HWP_CAPABILITIES.Guaranteed_Performance value to ascertain the
new Guaranteed Performance value and to assess whether to re-adjust HWP hints via IA32_HWP_REQUEST.
Software must clear this bit by writing a zero (0).
•
Excursion_To_Minimum (bit 2, RWC0) — If set (1), an excursion to Minimum_Performance of
IA32_HWP_REQUEST has occurred. Software must clear this bit by writing a zero (0).
•
Bits 63:3, and bit 1 are reserved and must be zero.
63
3 2 1 0
Reserved
Excursion_To_Minimum
Reserved
Guaranteed_Performance_Change
Figure 14-8. IA32_HWP_STATUS MSR
The status bits of IA32_HWP_STATUS must be cleared (0) by software so that a new status condition change will
cause the hardware to set the bit again and issue the notification. Status bits are not set for “normal” excursions
e.g. running below Minimum Performance for short durations during C-state exit. Changes to
Guaranteed_Performance and excursions to Minimum_Performance will occur no more than once per second.
The OS can determine the specific reasons for a Guaranteed_Performance change or an excursion to
Minimum_Performance in IA32_HWP_REQUEST by examining the associated status and log bits reported in the
IA32_THERM_STATUS MSR. The layout of the IA32_HWP_STATUS MSR that HWP uses to support software query of
HWP feedback is shown in Figure 14-9. The bit fields of IA32_THERM_STATUS associated with HWP feedback are
described below (Bit fields of IA32_THERM_STATUS unrelated to HWP can be found in Section 14.7.5.2).
63
32 31
27
23 22
16 15 14 13 12 11 10 9 8 7
6 5
4
3
2
Reserved
Reading Valid
Resolution in Deg. Celsius
Digital Readout
Cross-domain Limit Log
Cross-domain Limit Status
Current Limit Log
Current Limit Status
Power Limit Notification Log
Power Limit Notification Status
Thermal Threshold #2 Log
Thermal Threshold #2 Status
Thermal Threshold #1 Log
Thermal Threshold #1 Status
Critical Temperature Log
Critical Temperature Status
PROCHOT# or FORCEPR# Log
PROCHOT# or FORCEPR# Event
Thermal Status Log
Thermal Status
Figure 14-9. IA32_THERM_STATUS Register With HWP Feedback
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POWER AND THERMAL MANAGEMENT
•
•
Bits 11:0, See Section 14.7.5.2.
•
Current Limit Log (bit 13, RWC0) — If set (1), an electrical current limit has been exceeded that has
adversely impacted energy efficiency optimizations since the last clearing of this bit or a reset. This bit is sticky,
software may clear this bit by writing a zero (0).
•
Cross-domain Limit Status (bit 14, RO) — If set (1), indicates another hardware domain (e.g. processor
graphics) is currently limiting energy efficiency optimizations in the processor core domain.
•
Cross-domain Limit Log (bit 15, RWC0) — If set (1), indicates another hardware domain (e.g. processor
graphics) has limited energy efficiency optimizations in the processor core domain since the last clearing of this
bit or a reset. This bit is sticky, software may clear this bit by writing a zero (0).
•
Bits 63:16, See Section 14.7.5.2.
Current Limit Status (bit 12, RO) — If set (1), indicates an electrical current limit (e.g. Electrical Design
Point/IccMax) is being exceeded and is adversely impacting energy efficiency optimizations.
14.4.5.1
Non-Architectural HWP Feedback
The Productive Performance (MSR_PPERF) MSR (non-architectural) provides hardware's view of workload scalability, which is a rough assessment of the relationship between frequency and workload performance, to software.
The layout of the MSR_PPERF is shown in Figure 14-10.
63
0
PCNT - Productive Performance Count
Figure 14-10. MSR_PPERF MSR
•
PCNT (bits 63:0, RO) — Similar to IA32_APERF but only counts cycles perceived by hardware as contributing
to instruction execution (e.g. unhalted and unstalled cycles). This counter increments at the same rate as
IA32_APERF, where the ratio of (ΔPCNT/ΔACNT) is an indicator of workload scalability (0% to 100%). Note that
values in this register are valid even when HWP is not enabled.
14.4.6
HWP Notifications
Processors may support interrupt-based notification of changes to HWP status as indicated by CPUID. If supported,
the IA32_HWP_INTERRUPT MSR is used to enable interrupt-based notifications. Notification events, when enabled,
are delivered using the existing thermal LVT entry. The layout of the IA32_HWP_INTERRUPT is shown in
Figure 14-11. The bit fields are described below:
63
2 1 0
Reserved
EN_Excursion_Minimum
EN_Guaranteed_Performance_Change
Figure 14-11. IA32_HWP_INTERRUPT MSR
•
EN_Guaranteed_Performance_Change (bit 0, RW) — When set (1), an HWP Interrupt will be generated
whenever a change to the IA32_HWP_CAPABILITIES.Guaranteed_Performance occurs. The default value is 0
(Interrupt generation is disabled).
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•
EN_Excursion_Minimum (bit 1, RW) — When set (1), an HWP Interrupt will be generated whenever the
HWP hardware is unable to meet the IA32_HWP_REQUEST.Minimum_Performance setting. The default value is
0 (Interrupt generation is disabled).
•
Bits 63:2, and bit 1 are reserved and must be zero.
14.4.7
Recommendations for OS use of HWP Controls
Common Cases of Using HWP
The default HWP control field values are expected to be suitable for many applications. The OS can enable autonomous HWP for these common cases by
•
Setting IA32_HWP_REQUEST.Desired Performance = 0 (hardware autonomous selection determines the
performance target). Set IA32_HWP_REQUEST.Activity Window = 0 (enable HW dynamic selection of window
size).
To maximize HWP benefit for the common cases, the OS should set
•
•
IA32_HWP_REQUEST.Minimum_Performance = IA32_HWP_CAPABILITIES.Lowest_Performance and
IA32_HWP_REQUEST.Maximum_Performance = IA32_HWP_CAPABILITIES.Highest_Performance.
Setting IA32_HWP_REQUEST.Minimum_Performance = IA32_HWP_REQUEST.Maximum_Performance is functionally equivalent to using of the IA32_PERF_CTL interface and is therefore not recommended (bypassing HWP).
Calibrating HWP for Application-Specific HWP Optimization
In some applications, the OS may have Quality of Service requirements that may not be met by the default values.
The OS can characterize HWP by:
•
keeping IA32_HWP_REQUEST.Minimum_Performance = IA32_HWP_REQUEST.Maximum_Performance to
prevent non-linearity in the characterization process,
•
utilizing the range values enumerated from the IA32_HWP_CAPABILITIES MSR to program
IA32_HWP_REQUEST while executing workloads of interest and observing the power and performance result.
The power and performance result of characterization is also influenced by the IA32_HWP_REQUEST.Energy
Performance Preference field, which must also be characterized.
Characterization can be used to set IA32_HWP_REQUEST.Minimum_Performance to achieve the required QOS in
terms of performance. If IA32_HWP_REQUEST.Minimum_Performance is set higher than
IA32_HWP_CAPABILITIES.Guaranteed Performance then notification of excursions to Minimum Performance may
be continuous.
If autonomous selection does not deliver the required workload performance, the OS should assess the current
delivered effective frequency and for the duration of the specific performance requirement set
IA32_HWP_REQUEST.Desired_Performance ≠ 0 and adjust IA32_HWP_REQUEST.Energy_Performance_Preference
as necessary to achieve the required workload performance. The MSR_PPERF.PCNT value can be used to better
comprehend the potential performance result from adjustments to IA32_HWP_REQUEST.Desired_Performance.
The OS should set IA32_HWP_REQUEST.Desired_Performance = 0 to re-enable autonomous selection.
Tuning for Maximum Performance or Lowest Power Consumption
Maximum performance will be delivered by setting IA32_HWP_REQUEST.Minimum_Performance =
IA32_HWP_REQUEST.Maximum_Performance = IA32_HWP_CAPABILITIES.Highest_Performance and setting
IA32_HWP_REQUEST.Energy_Performance_Preference = 0 (performance preference).
Lowest power will be achieved by setting IA32_HWP_REQUEST.Minimum_Performance =
IA32_HWP_REQUEST.Maximum_Performance = IA32_HWP_CAPABILITIES.Lowest_Performance and setting
IA32_HWP_REQUEST.Energy_Performance_Preference = 0FFH (energy efficiency preference).
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POWER AND THERMAL MANAGEMENT
Additional Guidelines
Set IA32_HWP_REQUEST.Energy_Performance_Preference as appropriate for the platform's current mode of operation. For example, a mobile platforms' setting may be towards performance preference when on AC power and
more towards energy efficiency when on DC power.
The use of the Running Average Power Limit (RAPL) processor capability (see section 14.7.1) is highly recommended when HWP is enabled. Use of IA32_HWP_Request.Maximum_Performance for thermal control is subject to
limitations and can adversely impact the performance of other processor components e.g. Graphics
If default values deliver undesirable performance latency in response to events, the OS should set
IA32_HWP_REQUEST. Activity_Window to a low (non zero) value and
IA32_HWP_REQUEST.Energy_Performance_Preference towards performance (0) for the event duration.
Similarly, for “real-time” threads, set IA32_HWP_REQUEST.Energy_Performance_Preference towards performance
(0) and IA32_HWP_REQUEST. Activity_Window to a low value, e.g. 01H, for the duration of their execution.
When executing low priority work that may otherwise cause the hardware to deliver high performance, set
IA32_HWP_REQUEST. Activity_Window to a longer value and reduce the
IA32_HWP_Request.Maximum_Performance value as appropriate to control energy efficiency. Adjustments to
IA32_HWP_REQUEST.Energy_Performance_Preference may also be necessary.
14.5
HARDWARE DUTY CYCLING (HDC)
Intel processors may contain support for Hardware Duty Cycling (HDC), which enables the processor to autonomously force its components inside the physical package into idle state. For example, the processor may selectively
force only the processor cores into an idle state.
HDC is disabled by default on processors that support it. System software can dynamically enable or disable HDC
to force one or more components into an idle state or wake up those components previously forced into an idle
state. Forced Idling (and waking up) of multiple components in a physical package can be done with one WRMSR
to a packaged-scope MSR from any logical processor within the same package.
HDC does not delay events such as timer expiration, but it may affect the latency of short (less than 1 msec) software threads, e.g. if a thread is forced to idle state just before completion and entering a “natural idle”.
HDC forced idle operation can be thought of as operating at a lower effective frequency. The effective average
frequency computed by software will include the impact of HDC forced idle.
The primary use of HDC is enable system software to manage low active workloads to increase the package level
C6 residency. Additionally, HDC can lower the effective average frequency in case or power or thermal limitation.
When HDC forces a logical processor, a processor core or a physical package to enter an idle state, its C-State is set
to C3 or deeper. The deep “C-states” referred to in this section are processor-specific C-states.
14.5.1
Hardware Duty Cycling Programming Interfaces
The programming interfaces provided by HDC include the following:
•
The CPUID instruction allows software to discover the presence of HDC support in an Intel processor. Specifically, execute CPUID instruction with EAX=06H as input, bit 13 of EAX indicates the processor’s support of the
following aspects of HDC.
— Availability of HDC baseline resource, CPUID.06H:EAX[bit 13]: If this bit is set, HDC provides the following
architectural MSRs: IA32_PKG_HDC_CTL, IA32_PM_CTL1, and the IA32_THREAD_STALL MSRs.
•
Additionally, HDC may provide several non-architectural MSR.
Table 14-2. Architectural and non-Architecture MSRs Related to HDC
Address
Architec
tural
Register Name
Description
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Table 14-2. Architectural and non-Architecture MSRs Related to HDC
DB0H
Y
IA32_PKG_HDC_CTL
DB1H
Y
IA32_PM_CTL1
Package Enable/Disable HDC.
Per-logical-processor select control to allow/block HDC forced idling.
DB2H
Y
IA32_THREAD_STALL
653H
N
MSR_CORE_HDC_RESIDENCY
Accumulate stalled cycles on this logical processor due to HDC forced idling.
Core level stalled cycle counter due to HDC forced idling on one or more
logical processor.
655H
N
MSR_PKG_HDC_SHALLOW_RE
SIDENCY
Accumulate the cycles the package was in C21 state and at least one logical
processor was in forced idle
656H
N
MSR_PKG_HDC_DEEP_RESIDE
NCY
Accumulate the cycles the package was in the software specified Cx1 state
and at least one logical processor was in forced idle. Cx is specified in
MSR_PKG_HDC_CONFIG_CTL.
652H
N
MSR_PKG_HDC_CONFIG_CTL
HDC configuration controls
NOTES:
1. The package “C-states” referred to in this section are processor-specific C-states.
14.5.2
Package level Enabling HDC
The layout of the IA32_PKG_HDC_CTL MSR is shown in Figure 14-12. IA32_PKG_HDC_CTL is a writable MSR from
any logical processor in a package. The bit fields are described below:
63
1 0
Reserved
Reserved
HDC_PKG_Enable
Figure 14-12. IA32_PKG_HDC_CTL MSR
•
HDC_PKG_Enable (bit 0, R/W) — Software sets this bit to enable HDC operation by allowing the processor
to force to idle all “HDC-allowed” (see Figure 14.5.3) logical processors in the package. Clearing this bit
disables HDC operation in the package by waking up all the processor cores that were forced into idle by a
previous ‘0’-to-’1’ transition in IA32_PKG_HDC_CTL.HDC_PKG_Enable. This bit is writable only if
CPUID.06H:EAX[bit 13] = 1. Default = zero (0).
•
Bits 63:1 are reserved and must be zero.
After processor support is determined via CPUID, system software can enable HDC operation by setting
IA32_PKG_HDC_CTL.HDC_PKG_Enable to 1. At reset, IA32_PKG_HDC_CTL.HDC_PKG_Enable is cleared to 0. A
'0'-to-'1' transition in HDC_PKG_Enable allows the processor to force to idle all HDC-allowed (indicated by the nonzero state of IA32_PM_CTL1[bit 0]) logical processors in the package. A ‘1’-to-’0’ transition wakes up those HDC
force-idled logical processors.
Software can enable or disable HDC using this package level control multiple times from any logical processor in the
package. Note the latency of writing a value to the package-visible IA32_PKG_HDC_CTL.HDC_PKG_Enable is
longer than the latency of a WRMSR operation to a Logical Processor MSR (as opposed to package level MSR) such
as: IA32_PM_CTL1 (described in Section 14.5.3). Propagation of the change in
IA32_PKG_HDC_CTL.HDC_PKG_Enable and reaching all HDC idled logical processor to be woken up may take on
the order of core C6 exit latency.
14.5.3
Logical-Processor Level HDC Control
The layout of the IA32_PM_CTL1 MSR is shown in Figure 14-13. Each logical processor in a package has its own
IA32_PM_CTL1 MSR. The bit fields are described below:
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POWER AND THERMAL MANAGEMENT
63
1 0
Reserved
HDC_Allow_Block
Reserved
Figure 14-13. IA32_PM_CTL1 MSR
•
HDC_Allow_Block (bit 0, R/W) — Software sets this bit to allow this logical processors to honor the
package-level IA32_PKG_HDC_CTL.HDC_PKG_Enable control. Clearing this bit prevents this logical processor
from using the HDC. This bit is writable only if CPUID.06H:EAX[bit 13] = 1. Default = one (1).
•
Bits 63:1 are reserved and must be zero.
Fine-grain OS control of HDC operation at the granularity of per-logical-processor is provided by IA32_PM_CTL1.
At RESET, all logical processors are allowed to participate in HDC operation such that OS can manage HDC using
the package-level IA32_PKG_HDC_CTL.
Writes to IA32_PM_CTL1 complete with the latency that is typical to WRMSR to a Logical Processor level MSR.
When the OS chooses to manage HDC operation at per-logical-processor granularity, it can write to IA32_PM_CTL1
on one or more logical processors as desired. Each write to IA32_PM_CTL1 must be done by code that executes on
the logical processor targeted to be allowed into or blocked from HDC operation.
Blocking one logical processor for HDC operation may have package level impact. For example, the processor may
decide to stop duty cycling of all other Logical Processors as well.
The propagation of IA32_PKG_HDC_CTL.HDC_PKG_Enable in a package takes longer than a WRMSR to
IA32_PM_CTL1. The last completed write to IA32_PM_CTL1 on a logical processor will be honored when a ‘0’-to-’1’
transition of IA32_PKG_HDC_CTL.HDC_PKG_Enable arrives to a logical processor.
14.5.4
HDC Residency Counters
There is a collection of counters available for software to track various residency metrics related to HDC operation.
In general, HDC residency time is defined as the time in HDC forced idle state at the granularity of per-logicalprocessor, per-core, or package. At the granularity of per-core/package-level HDC residency, at least one of the
logical processor in a core/package must be in the HDC forced idle state.
14.5.4.1
IA32_THREAD_STALL
Software can track per-logical-processor HDC residency using the architectural MSR IA32_THREAD_STALL.The
layout of the IA32_THREAD_STALL MSR is shown in Figure 14-14. Each logical processor in a package has its own
IA32_THREAD_STALL MSR. The bit fields are described below:
63
0
Stall_cycle_cnt
Figure 14-14. IA32_THREAD_STALL MSR
•
Stall_Cycle_Cnt (bits 63:0, R/O) — Stores accumulated HDC forced-idle cycle count of this processor core
since last RESET. This counter increments at the same rate of the TSC. The count is updated only after the
logical processor exits from the forced idled C-state. At each update, the number of cycles that the logical
processor was stalled due to forced-idle will be added to the counter. This counter is available only if
CPUID.06H:EAX[bit 13] = 1. Default = zero (0).
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A value of zero in IA32_THREAD_STALL indicates either HDC is not supported or the logical processor never
serviced any forced HDC idle. A non-zero value in IA32_THREAD_STALL indicates the HDC forced-idle residency
times of the logical processor. It also indicates the forced-idle cycles due to HDC that could appear as C0 time to
traditional OS accounting mechanisms (e.g. time-stamping OS idle/exit events).
Software can read IA32_THREAD_STALL irrespective of the state of IA32_PKG_HDC_CTL and IA32_PM_CTL1, as
long as CPUID.06H:EAX[bit 13] = 1.
14.5.4.2
Non-Architectural HDC Residency Counters
Processors that support HDC operation may provide the following model-specific HDC residency counters.
MSR_CORE_HDC_RESIDENCY
Software can track per-core HDC residency using the counter MSR_CORE_HDC_RESIDENCY. This counter increments when the core is in C3 state or deeper (all logical processors in this core are idle due to either HDC or other
mechanisms) and at least one of the logical processors is in HDC forced idle state. The layout of the
MSR_CORE_HDC_RESIDENCY is shown in Figure 14-15. Each processor core in a package has its own
MSR_CORE_HDC_RESIDENCY MSR. The bit fields are described below:
63
0
Core_Cx_duty_cycle_cnt
Figure 14-15. MSR_CORE_HDC_RESIDENCY MSR
•
Core_Cx_Duty_Cycle_Cnt (bits 63:0, R/O) — Stores accumulated HDC forced-idle cycle count of this
processor core since last RESET. This counter increments at the same rate of the TSC. The count is updated only
after core C-state exit from a forced idled C-state. At each update, the increment counts cycles when the core
is in a Cx state (all its logical processor are idle) and at least one logical processor in this core was forced into
idle state due to HDC. If CPUID.06H:EAX[bit 13] = 0, attempt to access this MSR will cause a #GP fault. Default
= zero (0).
A value of zero in MSR_CORE_HDC_RESIDENCY indicates either HDC is not supported or this processor core never
serviced any forced HDC idle.
MSR_PKG_HDC_SHALLOW_RESIDENCY
The counter MSR_PKG_HDC_SHALLOW_RESIDENCY allows software to track HDC residency time when the
package is in C2 state, all processor cores in the package are not active and at least one logical processor was
forced into idle state due to HDC. The layout of the MSR_PKG_HDC_SHALLOW_RESIDENCY is shown in
Figure 14-16. There is one MSR_PKG_HDC_SHALLOW_RESIDENCY per package. The bit fields are described
below:
63
0
Pkg_Duty_cycle_cnt
Figure 14-16. MSR_PKG_HDC_SHALLOW_RESIDENCY MSR
•
Pkg_Duty_Cycle_Cnt (bits 63:0, R/O) — Stores accumulated HDC forced-idle cycle count of this processor
core since last RESET. This counter increments at the same rate of the TSC. Package shallow residency may be
implementation specific. In the initial implementation, the threshold is package C2-state. The count is
updated only after package C2-state exit from a forced idled C-state. At each update, the increment counts
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POWER AND THERMAL MANAGEMENT
cycles when the package is in C2 state and at least one processor core in this package was forced into idle state
due to HDC. If CPUID.06H:EAX[bit 13] = 0, attempt to access this MSR may cause a #GP fault. Default = zero
(0).
A value of zero in MSR_PKG_HDC_SHALLOW_RESIDENCY indicates either HDC is not supported or this processor
package never serviced any forced HDC idle.
MSR_PKG_HDC_DEEP_RESIDENCY
The counter MSR_PKG_HDC_DEEP_RESIDENCY allows software to track HDC residency time when the package is
in a software-specified package Cx state, all processor cores in the package are not active and at least one logical
processor was forced into idle state due to HDC. Selection of a specific package Cx state can be configured using
MSR_PKG_HDC_CONFIG. The layout of the MSR_PKG_HDC_DEEP_RESIDENCY is shown in Figure 14-17. There is
one MSR_PKG_HDC_DEEP_RESIDENCY per package. The bit fields are described below:
63
0
Pkg_Cx_duty_cycle_cnt
Figure 14-17. MSR_PKG_HDC_DEEP_RESIDENCY MSR
•
Pkg_Cx_Duty_Cycle_Cnt (bits 63:0, R/O) — Stores accumulated HDC forced-idle cycle count of this
processor core since last RESET. This counter increments at the same rate of the TSC. The count is updated
only after package C-state exit from a forced idle state. At each update, the increment counts cycles when the
package is in the software-configured Cx state and at least one processor core in this package was forced into
idle state due to HDC. If CPUID.06H:EAX[bit 13] = 0, attempt to access this MSR may cause a #GP fault.
Default = zero (0).
A value of zero in MSR_PKG_HDC_SHALLOW_RESIDENCY indicates either HDC is not supported or this processor
package never serviced any forced HDC idle.
MSR_PKG_HDC_CONFIG
MSR_PKG_HDC_CONFIG allows software to configure the package Cx state that the counter
MSR_PKG_HDC_DEEP_RESIDENCY monitors. The layout of the MSR_PKG_HDC_CONFIG is shown in Figure 14-18.
There is one MSR_PKG_HDC_CONFIG per package. The bit fields are described below:
2
63
0
Reserved
HDC_Cx_Monitor
Reserved
Figure 14-18. MSR_PKG_HDC_CONFIG MSR
•
Pkg_Cx_Monitor (bits 2:0, R/W) — Selects which package C-state the MSR_HDC_DEEP_RESIDENCY
counter will monitor. The encoding of the HDC_Cx_Monitor field are: 0: no-counting; 1: count package C2 only,
2: count package C3 and deeper; 3: count package C6 and deeper; 4: count package C7 and deeper; other
encodings are reserved. If CPUID.06H:EAX[bit 13] = 0, attempt to access this MSR may cause a #GP fault.
Default = zero (0).
•
Bits 63:3 are reserved and must be zero.
Vol. 3B 14-17
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14.5.5
MPERF and APERF Counters Under HDC
HDC operation can be thought of as an average effective frequency drop due to all or some of the Logical Processors enter an idle state period.
1600 MHz: 25% Utilization /75% Forced Idle
Effective Frequency @ 100% Utilization: 400 MHz
Figure 14-19. Example of Effective Frequency Reduction and Forced Idle Period of HDC
By default, the IA32_MPERF counter counts during forced idle periods as if the logical processor was active. The
IA32_APERF counter does not count during forced idle state. This counting convention allows the OS to compute
the average effective frequency of the Logical Processor between the last MWAIT exit and the next MWAIT entry
(OS visible C0) by ΔACNT/ΔMCNT * TSC Frequency.
14.6
MWAIT EXTENSIONS FOR ADVANCED POWER MANAGEMENT
IA-32 processors may support a number of C-states1 that reduce power consumption for inactive states. Intel Core
Solo and Intel Core Duo processors support both deeper C-state and MWAIT extensions that can be used by OS to
implement power management policy.
Software should use CPUID to discover if a target processor supports the enumeration of MWAIT extensions. If
CPUID.05H.ECX[Bit 0] = 1, the target processor supports MWAIT extensions and their enumeration (see Chapter
3, “Instruction Set Reference, A-M,” of Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume
2A).
If CPUID.05H.ECX[Bit 1] = 1, the target processor supports using interrupts as break-events for MWAIT, even
when interrupts are disabled. Use this feature to measure C-state residency as follows:
•
Software can write to bit 0 in the MWAIT Extensions register (ECX) when issuing an MWAIT to enter into a
processor-specific C-state or sub C-state.
•
When a processor comes out of an inactive C-state or sub C-state, software can read a timestamp before an
interrupt service routine (ISR) is potentially executed.
CPUID.05H.EDX allows software to enumerate processor-specific C-states and sub C-states available for use with
MWAIT extensions. IA-32 processors may support more than one C-state of a given C-state type. These are called
sub C-states. Numerically higher C-state have higher power savings and latency (upon entering and exiting) than
lower-numbered C-state.
At CPL = 0, system software can specify desired C-state and sub C-state by using the MWAIT hints register (EAX).
Processors will not go to C-state and sub C-state deeper than what is specified by the hint register. If CPL > 0 and
if MONITOR/MWAIT is supported at CPL > 0, the processor will only enter C1-state (regardless of the C-state
request in the hints register).
Executing MWAIT generates an exception on processors operating at a privilege level where MONITOR/MWAIT are
not supported.
1. The processor-specific C-states defined in MWAIT extensions can map to ACPI defined C-state types (C0, C1, C2, C3). The mapping
relationship depends on the definition of a C-state by processor implementation and is exposed to OSPM by the BIOS using the ACPI
defined _CST table.
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POWER AND THERMAL MANAGEMENT
NOTE
If MWAIT is used to enter a C-state (including sub C-state) that is numerically higher than C1, a
store to the address range armed by MONITOR instruction will cause the processor to exit MWAIT if
the store was originated by other processor agents. A store from non-processor agent may not
cause the processor to exit MWAIT.
14.7
THERMAL MONITORING AND PROTECTION
The IA-32 architecture provides the following mechanisms for monitoring temperature and controlling thermal
power:
1. The catastrophic shutdown detector forces processor execution to stop if the processor’s core temperature
rises above a preset limit.
2. Automatic and adaptive thermal monitoring mechanisms force the processor to reduce it’s power
consumption in order to operate within predetermined temperature limits.
3. The software controlled clock modulation mechanism permits operating systems to implement power
management policies that reduce power consumption; this is in addition to the reduction offered by automatic
thermal monitoring mechanisms.
4. On-die digital thermal sensor and interrupt mechanisms permit the OS to manage thermal conditions
natively without relying on BIOS or other system board components.
The first mechanism is not visible to software. The other three mechanisms are visible to software using processor
feature information returned by executing CPUID with EAX = 1.
The second mechanism includes:
•
Automatic thermal monitoring provides two modes of operation. One mode modulates the clock duty cycle;
the second mode changes the processor’s frequency. Both modes are used to control the core temperature of
the processor.
•
Adaptive thermal monitoring can provide flexible thermal management on processors made of multiple
cores.
The third mechanism modulates the clock duty cycle of the processor. As shown in Figure 14-20, the phrase ‘duty
cycle’ does not refer to the actual duty cycle of the clock signal. Instead it refers to the time period during which
the clock signal is allowed to drive the processor chip. By using the stop clock mechanism to control how often the
processor is clocked, processor power consumption can be modulated.
Clock Applied to Processor
Stop-Clock Duty Cycle
25% Duty Cycle (example only)
Figure 14-20. Processor Modulation Through Stop-Clock Mechanism
For previous automatic thermal monitoring mechanisms, software controlled mechanisms that changed processor
operating parameters to impact changes in thermal conditions. Software did not have native access to the native
thermal condition of the processor; nor could software alter the trigger condition that initiated software program
control.
The fourth mechanism (listed above) provides access to an on-die digital thermal sensor using a model-specific
register and uses an interrupt mechanism to alert software to initiate digital thermal monitoring.
Vol. 3B 14-19
POWER AND THERMAL MANAGEMENT
14.7.1
Catastrophic Shutdown Detector
P6 family processors introduced a thermal sensor that acts as a catastrophic shutdown detector. This catastrophic
shutdown detector was also implemented in Pentium 4, Intel Xeon and Pentium M processors. It is always enabled.
When processor core temperature reaches a factory preset level, the sensor trips and processor execution is halted
until after the next reset cycle.
14.7.2
Thermal Monitor
Pentium 4, Intel Xeon and Pentium M processors introduced a second temperature sensor that is factory-calibrated
to trip when the processor’s core temperature crosses a level corresponding to the recommended thermal design
envelop. The trip-temperature of the second sensor is calibrated below the temperature assigned to the catastrophic shutdown detector.
14.7.2.1
Thermal Monitor 1
The Pentium 4 processor uses the second temperature sensor in conjunction with a mechanism called Thermal
Monitor 1 (TM1) to control the core temperature of the processor. TM1 controls the processor’s temperature by
modulating the duty cycle of the processor clock. Modulation of duty cycles is processor model specific. Note that
the processors STPCLK# pin is not used here; the stop-clock circuitry is controlled internally.
Support for TM1 is indicated by CPUID.1:EDX.TM[bit 29] = 1.
TM1 is enabled by setting the thermal-monitor enable flag (bit 3) in IA32_MISC_ENABLE [see Chapter 35, “ModelSpecific Registers (MSRs),”]. Following a power-up or reset, the flag is cleared, disabling TM1. BIOS is required to
enable only one automatic thermal monitoring modes. Operating systems and applications must not disable the
operation of these mechanisms.
14.7.2.2
Thermal Monitor 2
An additional automatic thermal protection mechanism, called Thermal Monitor 2 (TM2), was introduced in the
Intel Pentium M processor and also incorporated in newer models of the Pentium 4 processor family. Intel Core Duo
and Solo processors, and Intel Core 2 Duo processor family all support TM1 and TM2. TM2 controls the core
temperature of the processor by reducing the operating frequency and voltage of the processor and offers a higher
performance level for a given level of power reduction than TM1.
TM2 is triggered by the same temperature sensor as TM1. The mechanism to enable TM2 may be implemented
differently across various IA-32 processor families with different CPUID signatures in the family encoding value, but
will be uniform within an IA-32 processor family.
Support for TM2 is indicated by CPUID.1:ECX.TM2[bit 8] = 1.
14.7.2.3
Two Methods for Enabling TM2
On processors with CPUID family/model/stepping signature encoded as 0x69n or 0x6Dn (early Pentium M processors), TM2 is enabled if the TM_SELECT flag (bit 16) of the MSR_THERM2_CTL register is set to 1 (Figure 14-21)
and bit 3 of the IA32_MISC_ENABLE register is set to 1.
Following a power-up or reset, the TM_SELECT flag may be cleared. BIOS is required to enable either TM1 or TM2.
Operating systems and applications must not disable mechanisms that enable TM1 or TM2. If bit 3 of the
IA32_MISC_ENABLE register is set and TM_SELECT flag of the MSR_THERM2_CTL register is cleared, TM1 is
enabled.
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POWER AND THERMAL MANAGEMENT
31
0
16
Reserved
Reserved
TM_SELECT
Figure 14-21. MSR_THERM2_CTL Register On Processors with CPUID Family/Model/Stepping Signature Encoded
as 0x69n or 0x6Dn
On processors introduced after the Pentium 4 processor (this includes most Pentium M processors), the method
used to enable TM2 is different. TM2 is enable by setting bit 13 of IA32_MISC_ENABLE register to 1. This applies to
Intel Core Duo, Core Solo, and Intel Core 2 processor family.
The target operating frequency and voltage for the TM2 transition after TM2 is triggered is specified by the value
written to MSR_THERM2_CTL, bits 15:0 (Figure 14-22). Following a power-up or reset, BIOS is required to enable
at least one of these two thermal monitoring mechanisms. If both TM1 and TM2 are supported, BIOS may choose
to enable TM2 instead of TM1. Operating systems and applications must not disable the mechanisms that enable
TM1or TM2; and they must not alter the value in bits 15:0 of the MSR_THERM2_CTL register.
15
63
0
Reserved
TM2 Transition Target
Figure 14-22. MSR_THERM2_CTL Register for Supporting TM2
14.7.2.4
Performance State Transitions and Thermal Monitoring
If the thermal control circuitry (TCC) for thermal monitor (TM1/TM2) is active, writes to the IA32_PERF_CTL will
effect a new target operating point as follows:
•
If TM1 is enabled and the TCC is engaged, the performance state transition can commence before the TCC is
disengaged.
•
If TM2 is enabled and the TCC is engaged, the performance state transition specified by a write to the
IA32_PERF_CTL will commence after the TCC has disengaged.
14.7.2.5
Thermal Status Information
The status of the temperature sensor that triggers the thermal monitor (TM1/TM2) is indicated through the
thermal status flag and thermal status log flag in the IA32_THERM_STATUS MSR (see Figure 14-23).
The functions of these flags are:
•
Thermal Status flag, bit 0 — When set, indicates that the processor core temperature is currently at the trip
temperature of the thermal monitor and that the processor power consumption is being reduced via either TM1
or TM2, depending on which is enabled. When clear, the flag indicates that the core temperature is below the
thermal monitor trip temperature. This flag is read only.
•
Thermal Status Log flag, bit 1 — When set, indicates that the thermal sensor has tripped since the last
power-up or reset or since the last time that software cleared this flag. This flag is a sticky bit; once set it
remains set until cleared by software or until a power-up or reset of the processor. The default state is clear.
Vol. 3B 14-21
POWER AND THERMAL MANAGEMENT
63
210
Reserved
Thermal Status Log
Thermal Status
Figure 14-23. IA32_THERM_STATUS MSR
After the second temperature sensor has been tripped, the thermal monitor (TM1/TM2) will remain engaged for a
minimum time period (on the order of 1 ms). The thermal monitor will remain engaged until the processor core
temperature drops below the preset trip temperature of the temperature sensor, taking hysteresis into account.
While the processor is in a stop-clock state, interrupts will be blocked from interrupting the processor. This holding
off of interrupts increases the interrupt latency, but does not cause interrupts to be lost. Outstanding interrupts
remain pending until clock modulation is complete.
The thermal monitor can be programmed to generate an interrupt to the processor when the thermal sensor is
tripped. The delivery mode, mask and vector for this interrupt can be programmed through the thermal entry in the
local APIC’s LVT (see Section 10.5.1, “Local Vector Table”). The low-temperature interrupt enable and high-temperature interrupt enable flags in the IA32_THERM_INTERRUPT MSR (see Figure 14-24) control when the interrupt is
generated; that is, on a transition from a temperature below the trip point to above and/or vice-versa.
63
210
Reserved
Low-Temperature Interrupt Enable
High-Temperature Interrupt Enable
Figure 14-24. IA32_THERM_INTERRUPT MSR
•
High-Temperature Interrupt Enable flag, bit 0 — Enables an interrupt to be generated on the transition
from a low-temperature to a high-temperature when set; disables the interrupt when clear.(R/W).
•
Low-Temperature Interrupt Enable flag, bit 1 — Enables an interrupt to be generated on the transition
from a high-temperature to a low-temperature when set; disables the interrupt when clear.
The thermal monitor interrupt can be masked by the thermal LVT entry. After a power-up or reset, the low-temperature interrupt enable and high-temperature interrupt enable flags in the IA32_THERM_INTERRUPT MSR are
cleared (interrupts are disabled) and the thermal LVT entry is set to mask interrupts. This interrupt should be
handled either by the operating system or system management mode (SMM) code.
Note that the operation of the thermal monitoring mechanism has no effect upon the clock rate of the processor's
internal high-resolution timer (time stamp counter).
14.7.2.6
Adaptive Thermal Monitor
The Intel Core 2 Duo processor family supports enhanced thermal management mechanism, referred to as Adaptive Thermal Monitor (Adaptive TM).
Unlike TM2, Adaptive TM is not limited to one TM2 transition target. During a thermal trip event, Adaptive TM (if
enabled) selects an optimal target operating point based on whether or not the current operating point has effectively cooled the processor.
Similar to TM2, Adaptive TM is enable by BIOS. The BIOS is required to test the TM1 and TM2 feature flags and
enable all available thermal control mechanisms (including Adaptive TM) at platform initiation.
Adaptive TM is available only to a subset of processors that support TM2.
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POWER AND THERMAL MANAGEMENT
In each chip-multiprocessing (CMP) silicon die, each core has a unique thermal sensor that triggers independently.
These thermal sensor can trigger TM1 or TM2 transitions in the same manner as described in Section 14.7.2.1 and
Section 14.7.2.2. The trip point of the thermal sensor is not programmable by software since it is set during the
fabrication of the processor.
Each thermal sensor in a processor core may be triggered independently to engage thermal management features.
In Adaptive TM, both cores will transition to a lower frequency and/or lower voltage level if one sensor is triggered.
Triggering of this sensor is visible to software via the thermal interrupt LVT entry in the local APIC of a given core.
14.7.3
Software Controlled Clock Modulation
Pentium 4, Intel Xeon and Pentium M processors also support software-controlled clock modulation. This provides
a means for operating systems to implement a power management policy to reduce the power consumption of the
processor. Here, the stop-clock duty cycle is controlled by software through the IA32_CLOCK_MODULATION MSR
(see Figure 14-25).
63
543
10
Reserved
On-Demand Clock Modulation Enable
On-Demand Clock Modulation Duty Cycle
Reserved
Figure 14-25. IA32_CLOCK_MODULATION MSR
The IA32_CLOCK_MODULATION MSR contains the following flag and field used to enable software-controlled clock
modulation and to select the clock modulation duty cycle:
•
On-Demand Clock Modulation Enable, bit 4 — Enables on-demand software controlled clock modulation
when set; disables software-controlled clock modulation when clear.
•
On-Demand Clock Modulation Duty Cycle, bits 1 through 3 — Selects the on-demand clock modulation
duty cycle (see Table 14-3). This field is only active when the on-demand clock modulation enable flag is set.
Note that the on-demand clock modulation mechanism (like the thermal monitor) controls the processor’s stopclock circuitry internally to modulate the clock signal. The STPCLK# pin is not used in this mechanism.
Table 14-3. On-Demand Clock Modulation Duty Cycle Field Encoding
Duty Cycle Field Encoding
Duty Cycle
000B
Reserved
001B
12.5% (Default)
010B
25.0%
011B
37.5%
100B
50.0%
101B
63.5%
110B
75%
111B
87.5%
The on-demand clock modulation mechanism can be used to control processor power consumption. Power
management software can write to the IA32_CLOCK_MODULATION MSR to enable clock modulation and to select
a modulation duty cycle. If on-demand clock modulation and TM1 are both enabled and the thermal status of the
processor is hot (bit 0 of the IA32_THERM_STATUS MSR is set), clock modulation at the duty cycle specified by TM1
takes precedence, regardless of the setting of the on-demand clock modulation duty cycle.
Vol. 3B 14-23
POWER AND THERMAL MANAGEMENT
For Hyper-Threading Technology enabled processors, the IA32_CLOCK_MODULATION register is duplicated for
each logical processor. In order for the On-demand clock modulation feature to work properly, the feature must be
enabled on all the logical processors within a physical processor. If the programmed duty cycle is not identical for
all the logical processors, the processor core clock will modulate to the highest duty cycle programmed for processors with any of the following CPUID DisplayFamily_DisplayModel signatures (see CPUID instruction in Chapter3,
“Instruction Set Reference, A-L” in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume
2A): 06_1A, 06_1C, 06_1E, 06_1F, 06_25, 06_26, 06_27, 06_2C, 06_2E, 06_2F, 06_35, 06_36, and 0F_xx. For all
other processors, if the programmed duty cycle is not identical for all logical processors in the same core, the
processor core will modulate at the lowest programmed duty cycle.
For multiple processor cores in a physical package, each processor core can modulate to a programmed duty cycle
independently.
For the P6 family processors, on-demand clock modulation was implemented through the chipset, which controlled
clock modulation through the processor’s STPCLK# pin.
14.7.3.1
Extension of Software Controlled Clock Modulation
Extension of the software controlled clock modulation facility supports on-demand clock modulation duty cycle with
4-bit dynamic range (increased from 3-bit range). Granularity of clock modulation duty cycle is increased to 6.25%
(compared to 12.5%).
Four bit dynamic range control is provided by using bit 0 in conjunction with bits 3:1 of the
IA32_CLOCK_MODULATION MSR (see Figure 14-26).
63
543
0
Reserved
On-Demand Clock Modulation Enable
Extended On-Demand Clock Modulation Duty Cycle
Reserved
Figure 14-26. IA32_CLOCK_MODULATION MSR with Clock Modulation Extension
Extension to software controlled clock modulation is supported only if CPUID.06H:EAX[Bit 5] = 1. If
CPUID.06H:EAX[Bit 5] = 0, then bit 0 of IA32_CLOCK_MODULATION is reserved.
14.7.4
Detection of Thermal Monitor and Software Controlled
Clock Modulation Facilities
The ACPI flag (bit 22) of the CPUID feature flags indicates the presence of the IA32_THERM_STATUS,
IA32_THERM_INTERRUPT, IA32_CLOCK_MODULATION MSRs, and the xAPIC thermal LVT entry.
The TM1 flag (bit 29) of the CPUID feature flags indicates the presence of the automatic thermal monitoring facilities that modulate clock duty cycles.
14.7.4.1
Detection of Software Controlled Clock Modulation Extension
Processor’s support of software controlled clock modulation extension is indicated by CPUID.06H:EAX[Bit 5] = 1.
14.7.5
On Die Digital Thermal Sensors
On die digital thermal sensor can be read using an MSR (no I/O interface). In Intel Core Duo processors, each core
has a unique digital sensor whose temperature is accessible using an MSR. The digital thermal sensor is the
preferred method for reading the die temperature because (a) it is located closer to the hottest portions of the die,
(b) it enables software to accurately track the die temperature and the potential activation of thermal throttling.
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POWER AND THERMAL MANAGEMENT
14.7.5.1
Digital Thermal Sensor Enumeration
The processor supports a digital thermal sensor if CPUID.06H.EAX[0] = 1. If the processor supports digital thermal
sensor, EBX[bits 3:0] determine the number of thermal thresholds that are available for use.
Software sets thermal thresholds by using the IA32_THERM_INTERRUPT MSR. Software reads output of the digital
thermal sensor using the IA32_THERM_STATUS MSR.
14.7.5.2
Reading the Digital Sensor
Unlike traditional analog thermal devices, the output of the digital thermal sensor is a temperature relative to the
maximum supported operating temperature of the processor.
Temperature measurements returned by digital thermal sensors are always at or below TCC activation temperature. Critical temperature conditions are detected using the “Critical Temperature Status” bit. When this bit is set,
the processor is operating at a critical temperature and immediate shutdown of the system should occur. Once the
“Critical Temperature Status” bit is set, reliable operation is not guaranteed.
See Figure 14-27 for the layout of IA32_THERM_STATUS MSR. Bit fields include:
•
Thermal Status (bit 0, RO) — This bit indicates whether the digital thermal sensor high-temperature output
signal (PROCHOT#) is currently active. Bit 0 = 1 indicates the feature is active. This bit may not be written by
software; it reflects the state of the digital thermal sensor.
•
Thermal Status Log (bit 1, R/WC0) — This is a sticky bit that indicates the history of the thermal sensor
high temperature output signal (PROCHOT#). Bit 1 = 1 if PROCHOT# has been asserted since a previous
RESET or the last time software cleared the bit. Software may clear this bit by writing a zero.
•
PROCHOT# or FORCEPR# Event (bit 2, RO) — Indicates whether PROCHOT# or FORCEPR# is being
asserted by another agent on the platform.
63
32 31
27
23 22
16 15
11 10 9 8 7
6 5
4
3
2
1 0
Reserved
Reading Valid
Resolution in Deg. Celsius
Digital Readout
Power Limit Notification Log
Power Limit Notification Status
Thermal Threshold #2 Log
Thermal Threshold #2 Status
Thermal Threshold #1 Log
Thermal Threshold #1 Status
Critical Temperature Log
Critical Temperature Status
PROCHOT# or FORCEPR# Log
PROCHOT# or FORCEPR# Event
Thermal Status Log
Thermal Status
Figure 14-27. IA32_THERM_STATUS Register
•
PROCHOT# or FORCEPR# Log (bit 3, R/WC0) — Sticky bit that indicates whether PROCHOT# or
FORCEPR# has been asserted by another agent on the platform since the last clearing of this bit or a reset. If
bit 3 = 1, PROCHOT# or FORCEPR# has been externally asserted. Software may clear this bit by writing a zero.
External PROCHOT# assertions are only acknowledged if the Bidirectional Prochot feature is enabled.
•
Critical Temperature Status (bit 4, RO) — Indicates whether the critical temperature detector output signal
is currently active. If bit 4 = 1, the critical temperature detector output signal is currently active.
Vol. 3B 14-25
POWER AND THERMAL MANAGEMENT
•
Critical Temperature Log (bit 5, R/WC0) — Sticky bit that indicates whether the critical temperature
detector output signal has been asserted since the last clearing of this bit or reset. If bit 5 = 1, the output
signal has been asserted. Software may clear this bit by writing a zero.
•
Thermal Threshold #1 Status (bit 6, RO) — Indicates whether the actual temperature is currently higher
than or equal to the value set in Thermal Threshold #1. If bit 6 = 0, the actual temperature is lower. If
bit 6 = 1, the actual temperature is greater than or equal to TT#1. Quantitative information of actual
temperature can be inferred from Digital Readout, bits 22:16.
•
Thermal Threshold #1 Log (bit 7, R/WC0) — Sticky bit that indicates whether the Thermal Threshold #1
has been reached since the last clearing of this bit or a reset. If bit 7 = 1, the Threshold #1 has been reached.
Software may clear this bit by writing a zero.
•
Thermal Threshold #2 Status (bit 8, RO) — Indicates whether actual temperature is currently higher than
or equal to the value set in Thermal Threshold #2. If bit 8 = 0, the actual temperature is lower. If bit 8 = 1, the
actual temperature is greater than or equal to TT#2. Quantitative information of actual temperature can be
inferred from Digital Readout, bits 22:16.
•
Thermal Threshold #2 Log (bit 9, R/WC0) — Sticky bit that indicates whether the Thermal Threshold #2
has been reached since the last clearing of this bit or a reset. If bit 9 = 1, the Thermal Threshold #2 has been
reached. Software may clear this bit by writing a zero.
•
Power Limitation Status (bit 10, RO) — Indicates whether the processor is currently operating below OSrequested P-state (specified in IA32_PERF_CTL) or OS-requested clock modulation duty cycle (specified in
IA32_CLOCK_MODULATION). This field is supported only if CPUID.06H:EAX[bit 4] = 1. Package level power
limit notification can be delivered independently to IA32_PACKAGE_THERM_STATUS MSR.
•
Power Notification Log (bit 11, R/WCO) — Sticky bit that indicates the processor went below OSrequested P-state or OS-requested clock modulation duty cycle since the last clearing of this or RESET. This
field is supported only if CPUID.06H:EAX[bit 4] = 1. Package level power limit notification is indicated independently in IA32_PACKAGE_THERM_STATUS MSR.
•
Digital Readout (bits 22:16, RO) — Digital temperature reading in 1 degree Celsius relative to the TCC
activation temperature.
0: TCC Activation temperature,
1: (TCC Activation - 1) , etc. See the processor’s data sheet for details regarding TCC activation.
A lower reading in the Digital Readout field (bits 22:16) indicates a higher actual temperature.
•
Resolution in Degrees Celsius (bits 30:27, RO) — Specifies the resolution (or tolerance) of the digital
thermal sensor. The value is in degrees Celsius. It is recommended that new threshold values be offset from the
current temperature by at least the resolution + 1 in order to avoid hysteresis of interrupt generation.
•
Reading Valid (bit 31, RO) — Indicates if the digital readout in bits 22:16 is valid. The readout is valid if
bit 31 = 1.
Changes to temperature can be detected using two thresholds (see Figure 14-28); one is set above and the other
below the current temperature. These thresholds have the capability of generating interrupts using the core's local
APIC which software must then service. Note that the local APIC entries used by these thresholds are also used by
the Intel® Thermal Monitor; it is up to software to determine the source of a specific interrupt.
14-26 Vol. 3B
POWER AND THERMAL MANAGEMENT
63
25 24 23 22
16 15 14
8
5
4
3
2
1
0
Reserved
Power Limit Notification Enable
Threshold #2 Interrupt Enable
Threshold #2 Value
Threshold #1 Interrupt Enable
Threshold #1 Value
Overheat Interrupt Enable
FORCPR# Interrupt Enable
PROCHOT# Interrupt Enable
Low Temp. Interrupt Enable
High Temp. Interrupt Enable
Figure 14-28. IA32_THERM_INTERRUPT Register
See Figure 14-28 for the layout of IA32_THERM_INTERRUPT MSR. Bit fields include:
•
High-Temperature Interrupt Enable (bit 0, R/W) — This bit allows the BIOS to enable the generation of
an interrupt on the transition from low-temperature to a high-temperature threshold. Bit 0 = 0 (default)
disables interrupts; bit 0 = 1 enables interrupts.
•
Low-Temperature Interrupt Enable (bit 1, R/W) — This bit allows the BIOS to enable the generation of an
interrupt on the transition from high-temperature to a low-temperature (TCC de-activation). Bit 1 = 0 (default)
disables interrupts; bit 1 = 1 enables interrupts.
•
PROCHOT# Interrupt Enable (bit 2, R/W) — This bit allows the BIOS or OS to enable the generation of an
interrupt when PROCHOT# has been asserted by another agent on the platform and the Bidirectional Prochot
feature is enabled. Bit 2 = 0 disables the interrupt; bit 2 = 1 enables the interrupt.
•
FORCEPR# Interrupt Enable (bit 3, R/W) — This bit allows the BIOS or OS to enable the generation of an
interrupt when FORCEPR# has been asserted by another agent on the platform. Bit 3 = 0 disables the
interrupt; bit 3 = 1 enables the interrupt.
•
Critical Temperature Interrupt Enable (bit 4, R/W) — Enables the generation of an interrupt when the
Critical Temperature Detector has detected a critical thermal condition. The recommended response to this
condition is a system shutdown. Bit 4 = 0 disables the interrupt; bit 4 = 1 enables the interrupt.
•
Threshold #1 Value (bits 14:8, R/W) — A temperature threshold, encoded relative to the TCC Activation
temperature (using the same format as the Digital Readout). This threshold is compared against the Digital
Readout and is used to generate the Thermal Threshold #1 Status and Log bits as well as the Threshold #1
thermal interrupt delivery.
•
Threshold #1 Interrupt Enable (bit 15, R/W) — Enables the generation of an interrupt when the actual
temperature crosses the Threshold #1 setting in any direction. Bit 15 = 1 enables the interrupt; bit 15 = 0
disables the interrupt.
•
Threshold #2 Value (bits 22:16, R/W) —A temperature threshold, encoded relative to the TCC Activation
temperature (using the same format as the Digital Readout). This threshold is compared against the Digital
Readout and is used to generate the Thermal Threshold #2 Status and Log bits as well as the Threshold #2
thermal interrupt delivery.
•
Threshold #2 Interrupt Enable (bit 23, R/W) — Enables the generation of an interrupt when the actual
temperature crosses the Threshold #2 setting in any direction. Bit 23 = 1enables the interrupt; bit 23 = 0
disables the interrupt.
•
Power Limit Notification Enable (bit 24, R/W) — Enables the generation of power notification events when
the processor went below OS-requested P-state or OS-requested clock modulation duty cycle. This field is
supported only if CPUID.06H:EAX[bit 4] = 1. Package level power limit notification can be enabled independently by IA32_PACKAGE_THERM_INTERRUPT MSR.
Vol. 3B 14-27
POWER AND THERMAL MANAGEMENT
14.7.6
Power Limit Notification
Platform firmware may be capable of specifying a power limit to restrict power delivered to a platform component,
such as a physical processor package. This constraint imposed by platform firmware may occasionally cause the
processor to operate below OS-requested P or T-state. A power limit notification event can be delivered using the
existing thermal LVT entry in the local APIC.
Software can enumerate the presence of the processor’s support for power limit notification by verifying
CPUID.06H:EAX[bit 4] = 1.
If CPUID.06H:EAX[bit 4] = 1, then IA32_THERM_INTERRUPT and IA32_THERM_STATUS provides the following
facility to manage power limit notification:
•
Bits 10 and 11 in IA32_THERM_STATUS informs software of the occurrence of processor operating below OSrequested P-state or clock modulation duty cycle setting (see Figure 14-27).
•
Bit 24 in IA32_THERM_INTERRUPT enables the local APIC to deliver a thermal event when the processor went
below OS-requested P-state or clock modulation duty cycle setting (see Figure 14-28).
14.8
PACKAGE LEVEL THERMAL MANAGEMENT
The thermal management facilities like IA32_THERM_INTERRUPT and IA32_THERM_STATUS are often implemented with a processor core granularity. To facilitate software manage thermal events from a package level granularity, two architectural MSR is provided for package level thermal management. The
IA32_PACKAGE_THERM_STATUS and IA32_PACKAGE_THERM_INTERRUPT MSRs use similar interfaces as
IA32_THERM_STATUS and IA32_THERM_INTERRUPT, but are shared in each physical processor package.
Software can enumerate the presence of the processor’s support for package level thermal management facility
(IA32_PACKAGE_THERM_STATUS and IA32_PACKAGE_THERM_INTERRUPT) by verifying CPUID.06H:EAX[bit 6] =
1.
The layout of IA32_PACKAGE_THERM_STATUS MSR is shown in Figure 14-29.
63
32 31
27
23 22
16 15
11 10 9 8 7
6 5
4
3
2
1 0
Reserved
PKG Digital Readout
PKG Power Limit Notification Log
PKG Power Limit Notification Status
PKG Thermal Threshold #2 Log
PKG Thermal Threshold #2 Status
PKG Thermal Threshold #1 Log
PKG Thermal Threshold #1 Status
PKG Critical Temperature Log
PKG Critical Temperature Status
PKG PROCHOT# or FORCEPR# Log
PKG PROCHOT# or FORCEPR# Event
PKG Thermal Status Log
PKG Thermal Status
Figure 14-29. IA32_PACKAGE_THERM_STATUS Register
•
Package Thermal Status (bit 0, RO) — This bit indicates whether the digital thermal sensor hightemperature output signal (PROCHOT#) for the package is currently active. Bit 0 = 1 indicates the feature is
active. This bit may not be written by software; it reflects the state of the digital thermal sensor.
14-28 Vol. 3B
POWER AND THERMAL MANAGEMENT
•
Package Thermal Status Log (bit 1, R/WC0) — This is a sticky bit that indicates the history of the thermal
sensor high temperature output signal (PROCHOT#) of the package. Bit 1 = 1 if package PROCHOT# has been
asserted since a previous RESET or the last time software cleared the bit. Software may clear this bit by writing
a zero.
•
Package PROCHOT# Event (bit 2, RO) — Indicates whether package PROCHOT# is being asserted by
another agent on the platform.
•
Package PROCHOT# Log (bit 3, R/WC0) — Sticky bit that indicates whether package PROCHOT# has been
asserted by another agent on the platform since the last clearing of this bit or a reset. If bit 3 = 1, package
PROCHOT# has been externally asserted. Software may clear this bit by writing a zero.
•
Package Critical Temperature Status (bit 4, RO) — Indicates whether the package critical temperature
detector output signal is currently active. If bit 4 = 1, the package critical temperature detector output signal
is currently active.
•
Package Critical Temperature Log (bit 5, R/WC0) — Sticky bit that indicates whether the package critical
temperature detector output signal has been asserted since the last clearing of this bit or reset. If bit 5 = 1, the
output signal has been asserted. Software may clear this bit by writing a zero.
•
Package Thermal Threshold #1 Status (bit 6, RO) — Indicates whether the actual package temperature is
currently higher than or equal to the value set in Package Thermal Threshold #1. If bit 6 = 0, the actual
temperature is lower. If bit 6 = 1, the actual temperature is greater than or equal to PTT#1. Quantitative
information of actual package temperature can be inferred from Package Digital Readout, bits 22:16.
•
Package Thermal Threshold #1 Log (bit 7, R/WC0) — Sticky bit that indicates whether the Package
Thermal Threshold #1 has been reached since the last clearing of this bit or a reset. If bit 7 = 1, the Package
Threshold #1 has been reached. Software may clear this bit by writing a zero.
•
Package Thermal Threshold #2 Status (bit 8, RO) — Indicates whether actual package temperature is
currently higher than or equal to the value set in Package Thermal Threshold #2. If bit 8 = 0, the actual
temperature is lower. If bit 8 = 1, the actual temperature is greater than or equal to PTT#2. Quantitative
information of actual temperature can be inferred from Package Digital Readout, bits 22:16.
•
Package Thermal Threshold #2 Log (bit 9, R/WC0) — Sticky bit that indicates whether the Package
Thermal Threshold #2 has been reached since the last clearing of this bit or a reset. If bit 9 = 1, the Package
Thermal Threshold #2 has been reached. Software may clear this bit by writing a zero.
•
Package Power Limitation Status (bit 10, RO) — Indicates package power limit is forcing one ore more
processors to operate below OS-requested P-state. Note that package power limit violation may be caused by
processor cores or by devices residing in the uncore. Software can examine IA32_THERM_STATUS to
determine if the cause originates from a processor core (see Figure 14-27).
•
Package Power Notification Log (bit 11, R/WCO) — Sticky bit that indicates any processor in the package
went below OS-requested P-state or OS-requested clock modulation duty cycle since the last clearing of this or
RESET.
•
Package Digital Readout (bits 22:16, RO) — Package digital temperature reading in 1 degree Celsius
relative to the package TCC activation temperature.
0: Package TCC Activation temperature,
1: (PTCC Activation - 1) , etc. See the processor’s data sheet for details regarding PTCC activation.
A lower reading in the Package Digital Readout field (bits 22:16) indicates a higher actual temperature.
The layout of IA32_PACKAGE_THERM_INTERRUPT MSR is shown in Figure 14-30.
Vol. 3B 14-29
POWER AND THERMAL MANAGEMENT
63
25 24 23 22
16 15 14
8
5
4
3
2
1
0
Reserved
Pkg Power Limit Notification Enable
Pkg Threshold #2 Interrupt Enable
Pkg Threshold #2 Value
Pkg Threshold #1 Interrupt Enable
Pkg Threshold #1 Value
Pkg Overheat Interrupt Enable
Pkg PROCHOT# Interrupt Enable
Pkg Low Temp. Interrupt Enable
Pkg High Temp. Interrupt Enable
Figure 14-30. IA32_PACKAGE_THERM_INTERRUPT Register
•
Package High-Temperature Interrupt Enable (bit 0, R/W) — This bit allows the BIOS to enable the
generation of an interrupt on the transition from low-temperature to a package high-temperature threshold.
Bit 0 = 0 (default) disables interrupts; bit 0 = 1 enables interrupts.
•
Package Low-Temperature Interrupt Enable (bit 1, R/W) — This bit allows the BIOS to enable the
generation of an interrupt on the transition from high-temperature to a low-temperature (TCC de-activation).
Bit 1 = 0 (default) disables interrupts; bit 1 = 1 enables interrupts.
•
Package PROCHOT# Interrupt Enable (bit 2, R/W) — This bit allows the BIOS or OS to enable the
generation of an interrupt when Package PROCHOT# has been asserted by another agent on the platform and
the Bidirectional Prochot feature is enabled. Bit 2 = 0 disables the interrupt; bit 2 = 1 enables the interrupt.
•
Package Critical Temperature Interrupt Enable (bit 4, R/W) — Enables the generation of an interrupt
when the Package Critical Temperature Detector has detected a critical thermal condition. The recommended
response to this condition is a system shutdown. Bit 4 = 0 disables the interrupt; bit 4 = 1 enables the
interrupt.
•
Package Threshold #1 Value (bits 14:8, R/W) — A temperature threshold, encoded relative to the
Package TCC Activation temperature (using the same format as the Digital Readout). This threshold is
compared against the Package Digital Readout and is used to generate the Package Thermal Threshold #1
Status and Log bits as well as the Package Threshold #1 thermal interrupt delivery.
•
Package Threshold #1 Interrupt Enable (bit 15, R/W) — Enables the generation of an interrupt when the
actual temperature crosses the Package Threshold #1 setting in any direction. Bit 15 = 1 enables the interrupt;
bit 15 = 0 disables the interrupt.
•
Package Threshold #2 Value (bits 22:16, R/W) —A temperature threshold, encoded relative to the PTCC
Activation temperature (using the same format as the Package Digital Readout). This threshold is compared
against the Package Digital Readout and is used to generate the Package Thermal Threshold #2 Status and Log
bits as well as the Package Threshold #2 thermal interrupt delivery.
•
Package Threshold #2 Interrupt Enable (bit 23, R/W) — Enables the generation of an interrupt when the
actual temperature crosses the Package Threshold #2 setting in any direction. Bit 23 = 1 enables the interrupt;
bit 23 = 0 disables the interrupt.
•
Package Power Limit Notification Enable (bit 24, R/W) — Enables the generation of package power
notification events.
14.8.1
Support for Passive and Active cooling
Passive and active cooling may be controlled by the OS power management agent through ACPI control methods.
On platforms providing package level thermal management facility described in the previous section, it is recommended that active cooling (FAN control) should be driven by measuring the package temperature using the
IA32_PACKAGE_THERM_INTERRUPT MSR.
14-30 Vol. 3B
POWER AND THERMAL MANAGEMENT
Passive cooling (frequency throttling) should be driven by measuring (a) the core and package temperatures, or
(b) only the package temperature. If measured package temperature led the power management agent to choose
which core to execute passive cooling, then all cores need to execute passive cooling. Core temperature is
measured using the IA32_THERMAL_STATUS and IA32_THERMAL_INTERRUPT MSRs. The exact implementation
details depend on the platform firmware and possible solutions include defining two different thermal zones (one
for core temperature and passive cooling and the other for package temperature and active cooling).
14.9
PLATFORM SPECIFIC POWER MANAGEMENT SUPPORT
This section covers power management interfaces that are not architectural but addresses the power management
needs of several platform specific components. Specifically, RAPL (Running Average Power Limit) interfaces
provide mechanisms to enforce power consumption limit. Power limiting usages have specific usages in client and
server platforms.
For client platform power limit control and for server platforms used in a data center, the following power and
thermal related usages are desirable:
•
Platform Thermal Management: Robust mechanisms to manage component, platform, and group-level
thermals, either proactively or reactively (e.g., in response to a platform-level thermal trip point).
•
Platform Power Limiting: More deterministic control over the system's power consumption, for example to
meet battery life targets on rack-level or container-level power consumption goals within a datacenter.
•
Power/Performance Budgeting: Efficient means to control the power consumed (and therefore the sustained
performance delivered) within and across platforms.
The server and client usage models are addressed by RAPL interfaces, which expose multiple domains of power
rationing within each processor socket. Generally, these RAPL domains may be viewed to include hierarchically:
•
•
Package domain is the processor die.
Memory domain includes the directly-attached DRAM; an additional power plane may constitute a separate
domain.
In order to manage the power consumed across multiple sockets via RAPL, individual limits must be programmed
for each processor complex. Programming specific RAPL domain across multiple sockets is not supported.
14.9.1
RAPL Interfaces
RAPL interfaces consist of non-architectural MSRs. Each RAPL domain supports the following set of capabilities,
some of which are optional as stated below.
•
•
•
Power limit - MSR interfaces to specify power limit, time window; lock bit, clamp bit etc.
•
Power Info (Optional) - Interface providing information on the range of parameters for a given domain,
minimum power, maximum power etc.
•
Policy (Optional) - 4-bit priority information that is a hint to hardware for dividing budget between sub-domains
in a parent domain.
Energy Status - Power metering interface providing energy consumption information.
Perf Status (Optional) - Interface providing information on the performance effects (regression) due to power
limits. It is defined as a duration metric that measures the power limit effect in the respective domain. The
meaning of duration is domain specific.
Each of the above capabilities requires specific units in order to describe them. Power is expressed in Watts, Time
is expressed in Seconds, and Energy is expressed in Joules. Scaling factors are supplied to each unit to make the
information presented meaningful in a finite number of bits. Units for power, energy, and time are exposed in the
read-only MSR_RAPL_POWER_UNIT MSR.
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POWER AND THERMAL MANAGEMENT
63
20 19
16 15 13 12
8 7
4
3
0
Reserved
Time units
Energy status units
Power units
Figure 14-31. MSR_RAPL_POWER_UNIT Register
MSR_RAPL_POWER_UNIT (Figure 14-31) provides the following information across all RAPL domains:
•
Power Units (bits 3:0): Power related information (in Watts) is based on the multiplier, 1/ 2^PU; where PU is
an unsigned integer represented by bits 3:0. Default value is 0011b, indicating power unit is in 1/8 Watts
increment.
•
Energy Status Units (bits 12:8): Energy related information (in Joules) is based on the multiplier, 1/2^ESU;
where ESU is an unsigned integer represented by bits 12:8. Default value is 10000b, indicating energy status
unit is in 15.3 micro-Joules increment.
•
Time Units (bits 19:16): Time related information (in Seconds) is based on the multiplier, 1/ 2^TU; where TU
is an unsigned integer represented by bits 19:16. Default value is 1010b, indicating time unit is in 976 microseconds increment.
14.9.2
RAPL Domains and Platform Specificity
The specific RAPL domains available in a platform vary across product segments. Platforms targeting the client
segment support the following RAPL domain hierarchy:
•
•
Package
Two power planes: PP0 and PP1 (PP1 may reflect to uncore devices)
Platforms targeting the server segment support the following RAPL domain hierarchy:
•
•
•
Package
Power plane: PP0
DRAM
Each level of the RAPL hierarchy provides a respective set of RAPL interface MSRs. Table 14-4 lists the RAPL MSR
interfaces available for each RAPL domain. The power limit MSR of each RAPL domain is located at offset 0 relative
to an MSR base address which is non-architectural (see Chapter 35). The energy status MSR of each domain is
located at offset 1 relative to the MSR base address of respective domain.
Table 14-4. RAPL MSR Interfaces and RAPL Domains
Domain
PKG
DRAM
PP0
14-32 Vol. 3B
Power Limit
(Offset 0)
MSR_PKG_POWER_
LIMIT
Energy Status (Offset
1)
MSR_PKG_ENERGY_STA RESERVED
TUS
MSR_DRAM_POWER MSR_DRAM_ENERGY_S
_LIMIT
TATUS
MSR_PP0_POWER_
LIMIT
Policy
(Offset 2)
RESERVED
MSR_PP0_ENERGY_STA MSR_PP0_POLICY
TUS
Perf Status
(Offset 3)
Power Info
(Offset 4)
MSR_PKG_PERF_STATUS
MSR_PKG_POWER_I
NFO
MSR_DRAM_PERF_STATUS
MSR_DRAM_POWER
_INFO
MSR_PP0_PERF_STATUS
RESERVED
POWER AND THERMAL MANAGEMENT
Table 14-4. RAPL MSR Interfaces and RAPL Domains
PP1
MSR_PP1_POWER_
LIMIT
MSR_PP1_ENERGY_STA MSR_PP1_POLICY
TUS
RESERVED
RESERVED
The presence of the optional MSR interfaces (the three right-most columns of Table 14-4) may be model-specific.
See Chapter 35 for detail.
14.9.3
Package RAPL Domain
The MSR interfaces defined for the package RAPL domain are:
•
MSR_PKG_POWER_LIMIT allows software to set power limits for the package and measurement attributes
associated with each limit,
•
•
MSR_PKG_ENERGY_STATUS reports measured actual energy usage,
MSR_PKG_POWER_INFO reports the package power range information for RAPL usage.
MSR_PKG_PERF_STATUS can report the performance impact of power limiting, but its availability may be modelspecific.
63 62
L
O
C
K
56 55
49 48 47 46
Time window
Power Limit #2
32 31
24 23
Pkg Power Limit #2
17 16 15 14
Time window
Power Limit #1
0
Pkg Power Limit #1
Enable limit #1
Pkg clamping limit #1
Enable limit #2
Pkg clamping limit #2
Figure 14-32. MSR_PKG_POWER_LIMIT Register
MSR_PKG_POWER_LIMIT allows a software agent to define power limitation for the package domain. Power limitation is defined in terms of average power usage (Watts) over a time window specified in MSR_PKG_POWER_LIMIT.
Two power limits can be specified, corresponding to time windows of different sizes. Each power limit provides
independent clamping control that would permit the processor cores to go below OS-requested state to meet the
power limits. A lock mechanism allow the software agent to enforce power limit settings. Once the lock bit is set,
the power limit settings are static and un-modifiable until next RESET.
The bit fields of MSR_PKG_POWER_LIMIT (Figure 14-32) are:
•
Package Power Limit #1(bits 14:0): Sets the average power usage limit of the package domain corresponding to time window # 1. The unit of this field is specified by the “Power Units” field of
MSR_RAPL_POWER_UNIT.
•
•
Enable Power Limit #1(bit 15): 0 = disabled; 1 = enabled.
•
Time Window for Power Limit #1 (bits 23:17): Indicates the time window for power limit #1
Package Clamping Limitation #1 (bit 16): Allow going below OS-requested P/T state setting during time
window specified by bits 23:17.
Time limit = 2^Y * (1.0 + Z/4.0) * Time_Unit
Here “Y” is the unsigned integer value represented. by bits 21:17, “Z” is an unsigned integer represented by
bits 23:22. “Time_Unit” is specified by the “Time Units” field of MSR_RAPL_POWER_UNIT.
Vol. 3B 14-33
POWER AND THERMAL MANAGEMENT
•
Package Power Limit #2(bits 46:32): Sets the average power usage limit of the package domain corresponding to time window # 2. The unit of this field is specified by the “Power Units” field of
MSR_RAPL_POWER_UNIT.
•
•
Enable Power Limit #2(bit 47): 0 = disabled; 1 = enabled.
•
Time Window for Power Limit #2 (bits 55:49): Indicates the time window for power limit #2
Package Clamping Limitation #2 (bit 48): Allow going below OS-requested P/T state setting during time
window specified by bits 23:17.
Time limit = 2^Y * (1.0 + Z/4.0) * Time_Unit
Here “Y” is the unsigned integer value represented. by bits 53:49, “Z” is an unsigned integer represented by
bits 55:54. “Time_Unit” is specified by the “Time Units” field of MSR_RAPL_POWER_UNIT. This field may have
a hard-coded value in hardware and ignores values written by software.
•
Lock (bit 63): If set, all write attempts to this MSR are ignored until next RESET.
MSR_PKG_ENERGY_STATUS is a read-only MSR. It reports the actual energy use for the package domain. This MSR
is updated every ~1msec. It has a wraparound time of around 60 secs when power consumption is high, and may
be longer otherwise.
32 31
63
0
Reserved
Total Energy Consumed
Reserved
Figure 14-33. MSR_PKG_ENERGY_STATUS MSR
•
Total Energy Consumed (bits 31:0): The unsigned integer value represents the total amount of energy
consumed since that last time this register is cleared. The unit of this field is specified by the “Energy Status
Units” field of MSR_RAPL_POWER_UNIT.
MSR_PKG_POWER_INFO is a read-only MSR. It reports the package power range information for RAPL usage. This
MSR provides maximum/minimum values (derived from electrical specification), thermal specification power of the
package domain. It also provides the largest possible time window for software to program the RAPL interface.
63
54 53
48 47 46
Maximum Time window
32 31 30
Maximum Power
Minimum Power
16 15 14
0
Thermal Spec Power
Figure 14-34. MSR_PKG_POWER_INFO Register
•
Thermal Spec Power (bits 14:0): The unsigned integer value is the equivalent of thermal specification power
of the package domain. The unit of this field is specified by the “Power Units” field of MSR_RAPL_POWER_UNIT.
•
Minimum Power (bits 30:16): The unsigned integer value is the equivalent of minimum power derived from
electrical spec of the package domain. The unit of this field is specified by the “Power Units” field of
MSR_RAPL_POWER_UNIT.
•
Maximum Power (bits 46:32): The unsigned integer value is the equivalent of maximum power derived from
the electrical spec of the package domain. The unit of this field is specified by the “Power Units” field of
MSR_RAPL_POWER_UNIT.
14-34 Vol. 3B
POWER AND THERMAL MANAGEMENT
•
Maximum Time Window (bits 53:48): The unsigned integer value is the equivalent of largest acceptable
value to program the time window of MSR_PKG_POWER_LIMIT. The unit of this field is specified by the “Time
Units” field of MSR_RAPL_POWER_UNIT.
MSR_PKG_PERF_STATUS is a read-only MSR. It reports the total time for which the package was throttled due to
the RAPL power limits. Throttling in this context is defined as going below the OS-requested P-state or T-state. It
has a wrap-around time of many hours. The availability of this MSR is platform specific (see Chapter 35).
32 31
63
0
Reserved
Accumulated pkg throttled time
Reserved
Figure 14-35. MSR_PKG_PERF_STATUS MSR
•
Accumulated Package Throttled Time (bits 31:0): The unsigned integer value represents the cumulative
time (since the last time this register is cleared) that the package has throttled. The unit of this field is specified
by the “Time Units” field of MSR_RAPL_POWER_UNIT.
14.9.4
PP0/PP1 RAPL Domains
The MSR interfaces defined for the PP0 and PP1 domains are identical in layout. Generally, PP0 refers to the
processor cores. The availability of PP1 RAPL domain interface is platform-specific. For a client platform, the PP1
domain refers to the power plane of a specific device in the uncore. For server platforms, the PP1 domain is not
supported, but its PP0 domain supports the MSR_PP0_PERF_STATUS interface.
•
MSR_PP0_POWER_LIMIT/MSR_PP1_POWER_LIMIT allow software to set power limits for the respective power
plane domain.
•
•
MSR_PP0_ENERGY_STATUS/MSR_PP1_ENERGY_STATUS report actual energy usage on a power plane.
MSR_PP0_POLICY/MSR_PP1_POLICY allow software to adjust balance for respective power plane.
MSR_PP0_PERF_STATUS can report the performance impact of power limiting, but it is not available in client platforms.
63
32 31 30
L
O
C
K
24 23
Time window
Power Limit
17 16 15 14
0
Power Limit
Enable limit
Clamping limit
Figure 14-36. MSR_PP0_POWER_LIMIT/MSR_PP1_POWER_LIMIT Register
MSR_PP0_POWER_LIMIT/MSR_PP1_POWER_LIMIT allow a software agent to define power limitation for the
respective power plane domain. A lock mechanism in each power plane domain allows the software agent to
enforce power limit settings independently. Once a lock bit is set, the power limit settings in that power plane are
static and un-modifiable until next RESET.
The bit fields of MSR_PP0_POWER_LIMIT/MSR_PP1_POWER_LIMIT (Figure 14-36) are:
•
Power Limit (bits 14:0): Sets the average power usage limit of the respective power plane domain. The unit
of this field is specified by the “Power Units” field of MSR_RAPL_POWER_UNIT.
Vol. 3B 14-35
POWER AND THERMAL MANAGEMENT
•
•
Enable Power Limit (bit 15): 0 = disabled; 1 = enabled.
•
Time Window for Power Limit (bits 23:17): Indicates the length of time window over which the power limit
#1 will be used by the processor. The numeric value encoded by bits 23:17 is represented by the product of
2^Y *F; where F is a single-digit decimal floating-point value between 1.0 and 1.3 with the fraction digit
represented by bits 23:22, Y is an unsigned integer represented by bits 21:17. The unit of this field is specified
by the “Time Units” field of MSR_RAPL_POWER_UNIT.
•
Lock (bit 31): If set, all write attempts to the MSR and corresponding policy
MSR_PP0_POLICY/MSR_PP1_POLICY are ignored until next RESET.
Clamping Limitation (bit 16): Allow going below OS-requested P/T state setting during time window specified
by bits 23:17.
MSR_PP0_ENERGY_STATUS/MSR_PP1_ENERGY_STATUS are read-only MSRs. They report the actual energy use
for the respective power plane domains. These MSRs are updated every ~1msec.
32 31
63
0
Reserved
Total Energy Consumed
Reserved
Figure 14-37. MSR_PP0_ENERGY_STATUS/MSR_PP1_ENERGY_STATUS MSR
•
Total Energy Consumed (bits 31:0): The unsigned integer value represents the total amount of energy
consumed since the last time this register was cleared. The unit of this field is specified by the “Energy Status
Units” field of MSR_RAPL_POWER_UNIT.
MSR_PP0_POLICY/MSR_PP1_POLICY provide balance power policy control for each power plane by providing
inputs to the power budgeting management algorithm. On platforms that support PP0 (IA cores) and PP1 (uncore
graphic device), the default values give priority to the non-IA power plane. These MSRs enable the PCU to balance
power consumption between the IA cores and uncore graphic device.
63
5 4
0
Priority Level
Figure 14-38. MSR_PP0_POLICY/MSR_PP1_POLICY Register
•
Priority Level (bits 4:0): Priority level input to the PCU for respective power plane. PP0 covers the IA
processor cores, PP1 covers the uncore graphic device. The value 31 is considered highest priority.
MSR_PP0_PERF_STATUS is a read-only MSR. It reports the total time for which the PP0 domain was throttled due
to the power limits. This MSR is supported only in server platform. Throttling in this context is defined as going
below the OS-requested P-state or T-state.
14-36 Vol. 3B
POWER AND THERMAL MANAGEMENT
32 31
63
0
Reserved
Accumulated PP0 throttled time
Reserved
Figure 14-39. MSR_PP0_PERF_STATUS MSR
•
Accumulated PP0 Throttled Time (bits 31:0): The unsigned integer value represents the cumulative time
(since the last time this register is cleared) that the PP0 domain has throttled. The unit of this field is specified
by the “Time Units” field of MSR_RAPL_POWER_UNIT.
14.9.5
DRAM RAPL Domain
The MSR interfaces defined for the DRAM domains are supported only in the server platform. The MSR interfaces
are:
•
MSR_DRAM_POWER_LIMIT allows software to set power limits for the DRAM domain and measurement
attributes associated with each limit.
•
•
•
MSR_DRAM_ENERGY_STATUS reports measured actual energy usage.
MSR_DRAM_POWER_INFO reports the DRAM domain power range information for RAPL usage.
MSR_DRAM_PERF_STATUS can report the performance impact of power limiting.
63
32 31 30
24 23
L
O
C
K
Time window
Power Limit
17 16 15 14
0
Power Limit
Enable limit
Clamping limit
Figure 14-40. MSR_DRAM_POWER_LIMIT Register
MSR_DRAM_POWER_LIMIT allows a software agent to define power limitation for the DRAM domain. Power limitation is defined in terms of average power usage (Watts) over a time window specified in
MSR_DRAM_POWER_LIMIT. A power limit can be specified along with a time window. A lock mechanism allow the
software agent to enforce power limit settings. Once the lock bit is set, the power limit settings are static and unmodifiable until next RESET.
The bit fields of MSR_DRAM_POWER_LIMIT (Figure 14-40) are:
•
DRAM Power Limit #1(bits 14:0): Sets the average power usage limit of the DRAM domain corresponding to
time window # 1. The unit of this field is specified by the “Power Units” field of MSR_RAPL_POWER_UNIT.
•
•
Enable Power Limit #1(bit 15): 0 = disabled; 1 = enabled.
•
Lock (bit 31): If set, all write attempts to this MSR are ignored until next RESET.
Time Window for Power Limit (bits 23:17): Indicates the length of time window over which the power limit
will be used by the processor. The numeric value encoded by bits 23:17 is represented by the product of 2^Y
*F; where F is a single-digit decimal floating-point value between 1.0 and 1.3 with the fraction digit
represented by bits 23:22, Y is an unsigned integer represented by bits 21:17. The unit of this field is specified
by the “Time Units” field of MSR_RAPL_POWER_UNIT.
Vol. 3B 14-37
POWER AND THERMAL MANAGEMENT
MSR_DRAM_ENERGY_STATUS is a read-only MSR. It reports the actual energy use for the DRAM domain. This MSR
is updated every ~1msec.
32 31
63
0
Reserved
Total Energy Consumed
Reserved
Figure 14-41. MSR_DRAM_ENERGY_STATUS MSR
•
Total Energy Consumed (bits 31:0): The unsigned integer value represents the total amount of energy
consumed since that last time this register is cleared. The unit of this field is specified by the “Energy Status
Units” field of MSR_RAPL_POWER_UNIT.
MSR_DRAM_POWER_INFO is a read-only MSR. It reports the DRAM power range information for RAPL usage. This
MSR provides maximum/minimum values (derived from electrical specification), thermal specification power of the
DRAM domain. It also provides the largest possible time window for software to program the RAPL interface.
63
54 53
48 47 46
Maximum Time window
32 31 30
Maximum Power
Minimum Power
16 15 14
0
Thermal Spec Power
Figure 14-42. MSR_DRAM_POWER_INFO Register
•
Thermal Spec Power (bits 14:0): The unsigned integer value is the equivalent of thermal specification power
of the DRAM domain. The unit of this field is specified by the “Power Units” field of MSR_RAPL_POWER_UNIT.
•
Minimum Power (bits 30:16): The unsigned integer value is the equivalent of minimum power derived from
electrical spec of the DRAM domain. The unit of this field is specified by the “Power Units” field of
MSR_RAPL_POWER_UNIT.
•
Maximum Power (bits 46:32): The unsigned integer value is the equivalent of maximum power derived from
the electrical spec of the DRAM domain. The unit of this field is specified by the “Power Units” field of
MSR_RAPL_POWER_UNIT.
•
Maximum Time Window (bits 53:48): The unsigned integer value is the equivalent of largest acceptable
value to program the time window of MSR_DRAM_POWER_LIMIT. The unit of this field is specified by the “Time
Units” field of MSR_RAPL_POWER_UNIT.
MSR_DRAM_PERF_STATUS is a read-only MSR. It reports the total time for which the package was throttled due to
the RAPL power limits. Throttling in this context is defined as going below the OS-requested P-state or T-state. It
has a wrap-around time of many hours. The availability of this MSR is platform specific (see Chapter 35).
32 31
63
Reserved
Accumulated DRAM throttled time
Reserved
Figure 14-43. MSR_DRAM_PERF_STATUS MSR
14-38 Vol. 3B
0
POWER AND THERMAL MANAGEMENT
•
Accumulated Package Throttled Time (bits 31:0): The unsigned integer value represents the cumulative
time (since the last time this register is cleared) that the DRAM domain has throttled. The unit of this field is
specified by the “Time Units” field of MSR_RAPL_POWER_UNIT.
Vol. 3B 14-39
POWER AND THERMAL MANAGEMENT
14-40 Vol. 3B
CHAPTER 15
MACHINE-CHECK ARCHITECTURE
This chapter describes the machine-check architecture and machine-check exception mechanism found in the
Pentium 4, Intel Xeon, Intel Atom, and P6 family processors. See Chapter 6, “Interrupt 18—Machine-Check Exception (#MC),” for more information on machine-check exceptions. A brief description of the Pentium processor’s
machine check capability is also given.
Additionally, a signaling mechanism for software to respond to hardware corrected machine check error is covered.
15.1
MACHINE-CHECK ARCHITECTURE
The Pentium 4, Intel Xeon, Intel Atom, and P6 family processors implement a machine-check architecture that
provides a mechanism for detecting and reporting hardware (machine) errors, such as: system bus errors, ECC
errors, parity errors, cache errors, and TLB errors. It consists of a set of model-specific registers (MSRs) that are
used to set up machine checking and additional banks of MSRs used for recording errors that are detected.
The processor signals the detection of an uncorrected machine-check error by generating a machine-check exception (#MC), which is an abort class exception. The implementation of the machine-check architecture does not
ordinarily permit the processor to be restarted reliably after generating a machine-check exception. However, the
machine-check-exception handler can collect information about the machine-check error from the machine-check
MSRs.
Starting with 45 nm Intel 64 processor on which CPUID reports DisplayFamily_DisplayModel as 06H_1AH (see
CPUID instruction in Chapter 3, “Instruction Set Reference, A-M” in the Intel® 64 and IA-32 Architectures Software
Developer’s Manual, Volume 2A), the processor can report information on corrected machine-check errors and
deliver a programmable interrupt for software to respond to MC errors, referred to as corrected machine-check
error interrupt (CMCI). See Section 15.5 for detail.
Intel 64 processors supporting machine-check architecture and CMCI may also support an additional enhancement, namely, support for software recovery from certain uncorrected recoverable machine check errors. See
Section 15.6 for detail.
15.2
COMPATIBILITY WITH PENTIUM PROCESSOR
The Pentium 4, Intel Xeon, Intel Atom, and P6 family processors support and extend the machine-check exception
mechanism introduced in the Pentium processor. The Pentium processor reports the following machine-check
errors:
•
•
data parity errors during read cycles
unsuccessful completion of a bus cycle
The above errors are reported using the P5_MC_TYPE and P5_MC_ADDR MSRs (implementation specific for the
Pentium processor). Use the RDMSR instruction to read these MSRs. See Chapter 35, “Model-Specific Registers
(MSRs),” for the addresses.
The machine-check error reporting mechanism that Pentium processors use is similar to that used in Pentium 4,
Intel Xeon, Intel Atom, and P6 family processors. When an error is detected, it is recorded in P5_MC_TYPE and
P5_MC_ADDR; the processor then generates a machine-check exception (#MC).
See Section 15.3.3, “Mapping of the Pentium Processor Machine-Check Errors to the Machine-Check Architecture,”
and Section 15.10.2, “Pentium Processor Machine-Check Exception Handling,” for information on compatibility
between machine-check code written to run on the Pentium processors and code written to run on P6 family
processors.
Vol. 3B 15-1
MACHINE-CHECK ARCHITECTURE
15.3
MACHINE-CHECK MSRS
Machine check MSRs in the Pentium 4, Intel Atom, Intel Xeon, and P6 family processors consist of a set of global
control and status registers and several error-reporting register banks. See Figure 15-1.
Error-Reporting Bank Registers
(One Set for Each Hardware Unit)
Global Control MSRs
63
0
63
IA32_MCG_CAP MSR
63
0
63
IA32_MCG_STATUS MSR
63
IA32_MCG_CTL MSR
0
IA32_MCi_ADDR MSR
0
63
0
IA32_MCi_STATUS MSR
0
63
0
IA32_MCi_CTL MSR
63
IA32_MCG_EXT_CTL MSR
0
IA32_MCi_MISC MSR
0
63
IA32_MCi_CTL2 MSR
Figure 15-1. Machine-Check MSRs
Each error-reporting bank is associated with a specific hardware unit (or group of hardware units) in the processor.
Use RDMSR and WRMSR to read and to write these registers.
15.3.1
Machine-Check Global Control MSRs
The machine-check global control MSRs include the IA32_MCG_CAP, IA32_MCG_STATUS, and optionally
IA32_MCG_CTL and IA32_MCG_EXT_CTL. See Chapter 35, “Model-Specific Registers (MSRs),” for the addresses of
these registers.
15.3.1.1
IA32_MCG_CAP MSR
The IA32_MCG_CAP MSR is a read-only register that provides information about the machine-check architecture of
the processor. Figure 15-2 shows the layout of the register.
15-2 Vol. 3B
MACHINE-CHECK ARCHITECTURE
63
27 26
25 24 23
16 15
0
12 11 10 9 8 7
Count
Reserved
MCG_LMCE_P[27]
MCG_ELOG_P[26]
MCG_EMC_P[25]
MCG_SER_P[24]
MCG_EXT_CNT[23:16]
MCG_TES_P[11]
MCG_CMCI_P[10]
MCG_EXT_P[9]
MCG_CTL_P[8]
Figure 15-2. IA32_MCG_CAP Register
Where:
•
Count field, bits 7:0 — Indicates the number of hardware unit error-reporting banks available in a particular
processor implementation.
•
MCG_CTL_P (control MSR present) flag, bit 8 — Indicates that the processor implements the
IA32_MCG_CTL MSR when set; this register is absent when clear.
•
MCG_EXT_P (extended MSRs present) flag, bit 9 — Indicates that the processor implements the extended
machine-check state registers found starting at MSR address 180H; these registers are absent when clear.
•
MCG_CMCI_P (Corrected MC error counting/signaling extension present) flag, bit 10 — Indicates
(when set) that extended state and associated MSRs necessary to support the reporting of an interrupt on a
corrected MC error event and/or count threshold of corrected MC errors, is present. When this bit is set, it does
not imply this feature is supported across all banks. Software should check the availability of the necessary
logic on a bank by bank basis when using this signaling capability (i.e. bit 30 settable in individual
IA32_MCi_CTL2 register).
•
MCG_TES_P (threshold-based error status present) flag, bit 11 — Indicates (when set) that bits 56:53
of the IA32_MCi_STATUS MSR are part of the architectural space. Bits 56:55 are reserved, and bits 54:53 are
used to report threshold-based error status. Note that when MCG_TES_P is not set, bits 56:53 of the
IA32_MCi_STATUS MSR are model-specific.
•
MCG_EXT_CNT, bits 23:16 — Indicates the number of extended machine-check state registers present. This
field is meaningful only when the MCG_EXT_P flag is set.
•
MCG_SER_P (software error recovery support present) flag, bit 24 — Indicates (when set) that the
processor supports software error recovery (see Section 15.6), and IA32_MCi_STATUS MSR bits 56:55 are
used to report the signaling of uncorrected recoverable errors and whether software must take recovery
actions for uncorrected errors. Note that when MCG_TES_P is not set, bits 56:53 of the IA32_MCi_STATUS MSR
are model-specific. If MCG_TES_P is set but MCG_SER_P is not set, bits 56:55 are reserved.
•
MCG_EMC_P (Enhanced Machine Check Capability) flag, bit 25 — Indicates (when set) that the
processor supports enhanced machine check capabilities for firmware first signaling.
•
MCG_ELOG_P (extended error logging) flag, bit 26 — Indicates (when set) that the processor allows
platform firmware to be invoked when an error is detected so that it may provide additional platform specific
information in an ACPI format “Generic Error Data Entry” that augments the data included in machine check
bank registers.
For additional information about extended error logging interface, see
http://www.intel.com/content/www/us/en/architecture-and-technology/enhanced-mca-logging-xeonpaper.html
Vol. 3B 15-3
MACHINE-CHECK ARCHITECTURE
•
MCG_LMCE_P (local machine check exception) flag, bit 27 — Indicates (when set) that the following
interfaces are present:
— an extended state LMCE_S (located in bit 3 of IA32_MCG_STATUS), and
— the IA32_MCG_EXT_CTL MSR, necessary to support Local Machine Check Exception (LMCE).
A non-zero MCG_LMCE_P indicates that, when LMCE is enabled as described in Section 15.3.1.5, some machine
check errors may be delivered to only a single logical processor.
The effect of writing to the IA32_MCG_CAP MSR is undefined.
15.3.1.2
IA32_MCG_STATUS MSR
The IA32_MCG_STATUS MSR describes the current state of the processor after a machine-check exception has
occurred (see Figure 15-3).
63
3 2 1 0
Reserved
M
C
I
P
E R
I I
P P
V V
LMCE_S—Local machine check exception signaled
MCIP—Machine check in progress flag
EIPV—Error IP valid flag
RIPV—Restart IP valid flag
Figure 15-3. IA32_MCG_STATUS Register
Where:
•
RIPV (restart IP valid) flag, bit 0 — Indicates (when set) that program execution can be restarted reliably
at the instruction pointed to by the instruction pointer pushed on the stack when the machine-check exception
is generated. When clear, the program cannot be reliably restarted at the pushed instruction pointer.
•
EIPV (error IP valid) flag, bit 1 — Indicates (when set) that the instruction pointed to by the instruction
pointer pushed onto the stack when the machine-check exception is generated is directly associated with the
error. When this flag is cleared, the instruction pointed to may not be associated with the error.
•
MCIP (machine check in progress) flag, bit 2 — Indicates (when set) that a machine-check exception was
generated. Software can set or clear this flag. The occurrence of a second Machine-Check Event while MCIP is
set will cause the processor to enter a shutdown state. For information on processor behavior in the shutdown
state, please refer to the description in Chapter 6, “Interrupt and Exception Handling”: “Interrupt 8—Double
Fault Exception (#DF)”.
•
LMCE_S (local machine check exception signaled), bit 3 — Indicates (when set) that a local machinecheck exception was generated. This indicates that the current machine-check event was delivered to only this
logical processor.
Bits 63:04 in IA32_MCG_STATUS are reserved. An attempt to write to IA32_MCG_STATUS with any value other
than 0 would result in #GP.
15.3.1.3
IA32_MCG_CTL MSR
The IA32_MCG_CTL MSR is present if the capability flag MCG_CTL_P is set in the IA32_MCG_CAP MSR.
IA32_MCG_CTL controls the reporting of machine-check exceptions. If present, writing 1s to this register enables
machine-check features and writing all 0s disables machine-check features. All other values are undefined and/or
implementation specific.
15-4 Vol. 3B
MACHINE-CHECK ARCHITECTURE
15.3.1.4
IA32_MCG_EXT_CTL MSR
The IA32_MCG_EXT_CTL MSR is present if the capability flag MCG_LMCE_P is set in the IA32_MCG_CAP MSR.
IA32_MCG_EXT_CTL.LMCE_EN (bit 0) allows the processor to signal some MCEs to only a single logical processor
in the system.
If MCG_LMCE_P is not set in IA32_MCG_CAP, or platform software has not enabled LMCE by setting
IA32_FEATURE_CONTROL.LMCE_ON (bit 20), any attempt to write or read IA32_MCG_EXT_CTL will result in #GP.
The IA32_MCG_EXT_CTL MSR is cleared on RESET.
Figure 15-4 shows the layout of the IA32_MCG_EXT_CTL register
63
1 0
Reserved
LMCE_EN - system software control to enable/disable LMCE
Figure 15-4. IA32_MCG_EXT_CTL Register
where
•
LMCE_EN (local machine check exception enable) flag, bit 0 - System software sets this to allow
hardware to signal some MCEs to only a single logical processor. System software can set LMCE_EN only if the
platform software has configured IA32_FEATURE_CONTROL as described in Section 15.3.1.5.
15.3.1.5
Enabling Local Machine Check
The intended usage of LMCE requires proper configuration by both platform software and system software. Platform software can turn LMCE on by setting bit 20 (LMCE_ON) in IA32_FEATURE_CONTROL MSR (MSR address
3AH).
System software must ensure that both IA32_FEATURE_CONTROL.Lock (bit 0)and
IA32_FEATURE_CONTROL.LMCE_ON (bit 20) are set before attempting to set IA32_MCG_EXT_CTL.LMCE_EN (bit
0). When system software has enabled LMCE, then hardware will determine if a particular error can be delivered
only to a single logical processor. Software should make no assumptions about the type of error that hardware can
choose to deliver as LMCE. The severity and override rules stay the same as described in Table 15-7 to determine
the recovery actions.
15.3.2
Error-Reporting Register Banks
Each error-reporting register bank can contain the IA32_MCi_CTL, IA32_MCi_STATUS, IA32_MCi_ADDR, and
IA32_MCi_MISC MSRs. The number of reporting banks is indicated by bits [7:0] of IA32_MCG_CAP MSR (address
0179H). The first error-reporting register (IA32_MC0_CTL) always starts at address 400H.
See Chapter 35, “Model-Specific Registers (MSRs),” for addresses of the error-reporting registers in the Pentium 4,
Intel Atom, and Intel Xeon processors; and for addresses of the error-reporting registers P6 family processors.
15.3.2.1
IA32_MCi_CTL MSRs
The IA32_MCi_CTL MSR controls signaling of #MC for errors produced by a particular hardware unit (or group of
hardware units). Each of the 64 flags (EEj) represents a potential error. Setting an EEj flag enables signaling #MC
of the associated error and clearing it disables signaling of the error. Error logging happens regardless of the
setting of these bits. The processor drops writes to bits that are not implemented. Figure 15-5 shows the bit fields
of IA32_MCi_CTL.
Vol. 3B 15-5
MACHINE-CHECK ARCHITECTURE
63 62 61
E
E
6
3
E
E
6
2
.....
E
E
6
1
3 2 1 0
E
E
0
2
E E
E E
0 0
1 0
EEj—Error reporting enable flag
(where j is 00 through 63)
Figure 15-5. IA32_MCi_CTL Register
NOTE
For P6 family processors, processors based on Intel Core microarchitecture (excluding those on
which on which CPUID reports DisplayFamily_DisplayModel as 06H_1AH and onward): the
operating system or executive software must not modify the contents of the IA32_MC0_CTL MSR.
This MSR is internally aliased to the EBL_CR_POWERON MSR and controls platform-specific error
handling features. System specific firmware (the BIOS) is responsible for the appropriate initialization of the IA32_MC0_CTL MSR. P6 family processors only allow the writing of all 1s or all 0s to
the IA32_MCi_CTL MSR.
15.3.2.2
IA32_MCi_STATUS MSRS
Each IA32_MCi_STATUS MSR contains information related to a machine-check error if its VAL (valid) flag is set (see
Figure 15-6). Software is responsible for clearing IA32_MCi_STATUS MSRs by explicitly writing 0s to them; writing
1s to them causes a general-protection exception.
NOTE
Figure 15-6 depicts the IA32_MCi_STATUS MSR when IA32_MCG_CAP[24] = 1,
IA32_MCG_CAP[11] = 1 and IA32_MCG_CAP[10] = 1. When IA32_MCG_CAP[24] = 0 and
IA32_MCG_CAP[11] = 1, bits 56:55 is reserved and bits 54:53 for threshold-based error reporting.
When IA32_MCG_CAP[11] = 0, bits 56:53 are part of the “Other Information” field. The use of bits
54:53 for threshold-based error reporting began with Intel Core Duo processors, and is currently
used for cache memory. See Section 15.4, “Enhanced Cache Error reporting,” for more information.
When IA32_MCG_CAP[10] = 0, bits 52:38 are part of the “Other Information” field. The use of bits
52:38 for corrected MC error count is introduced with Intel 64 processor on which CPUID reports
DisplayFamily_DisplayModel as 06H_1AH.
Where:
•
MCA (machine-check architecture) error code field, bits 15:0 — Specifies the machine-check architecture-defined error code for the machine-check error condition detected. The machine-check architecturedefined error codes are guaranteed to be the same for all IA-32 processors that implement the machine-check
architecture. See Section 15.9, “Interpreting the MCA Error Codes,” and Chapter 16, “Interpreting MachineCheck Error Codes”, for information on machine-check error codes.
•
Model-specific error code field, bits 31:16 — Specifies the model-specific error code that uniquely
identifies the machine-check error condition detected. The model-specific error codes may differ among IA-32
processors for the same machine-check error condition. See Chapter 16, “Interpreting Machine-Check Error
Codes”for information on model-specific error codes.
•
Reserved, Error Status, and Other Information fields, bits 56:32 —
•
If IA32_MCG_CAP.MCG_EMC_P[bit 25] is 0, bits 37:32 contain “Other Information” that is implementation-specific and is not part of the machine-check architecture.
•
If IA32_MCG_CAP.MCG_EMC_P is 1, “Other Information” is in bits 36:32. If bit 37 is 0, system firmware
has not changed the contents of IA32_MCi_STATUS. If bit 37 is 1, system firmware may have edited the
contents of IA32_MCi_STATUS.
•
If IA32_MCG_CAP.MCG_CMCI_P[bit 10] is 0, bits 52:38 also contain “Other Information” (in the same
sense as bits 37:32).
15-6 Vol. 3B
MACHINE-CHECK ARCHITECTURE
63 62 61 60 59 58 57 56 55 54 53 52
V O U E
A V C N
L E
R
P S A
C
R
C
Corrected Error
Count
38 37 36
32 31
Other
Info
16 15
MSCOD Model
Specific Error Code
0
MCA Error Code
Firmware updated error status indicator (37)*
Threshold-based error status (54:53)**
AR — Recovery action required for UCR error (55)***
S — Signaling an uncorrected recoverable (UCR) error (56)***
PCC — Processor context corrupted (57)
ADDRV — MCi_ADDR register valid (58)
MISCV — MCi_MISC register valid (59)
EN — Error reporting enabled (60)
UC — Uncorrected error (61)
OVER — Error overflow (62)
VAL — MCi_STATUS register valid (63)
* When IA32_MCG_CAP[25] (MCG_EMC_P) is set, bit 37 is not part of “Other Information”.
** When IA32_MCG_CAP[11] (MCG_TES_P) is not set, these bits are model-specific
(part of “Other Information”).
*** When IA32_MCG_CAP[11] or IA32_MCG_CAP[24] are not set, these bits are reserved, or
model-specific (part of “Other Information”).
Figure 15-6. IA32_MCi_STATUS Register
•
If IA32_MCG_CAP[10] is 1, bits 52:38 are architectural (not model-specific). In this case, bits 52:38
reports the value of a 15 bit counter that increments each time a corrected error is observed by the MCA
recording bank. This count value will continue to increment until cleared by software. The most
significant bit, 52, is a sticky count overflow bit.
•
•
If IA32_MCG_CAP[11] is 0, bits 56:53 also contain “Other Information” (in the same sense).
If IA32_MCG_CAP[11] is 1, bits 56:53 are architectural (not model-specific). In this case, bits 56:53
have the following functionality:
•
•
•
If IA32_MCG_CAP[24] is 0, bits 56:55 are reserved.
If IA32_MCG_CAP[24] is 1, bits 56:55 are defined as follows:
S (Signaling) flag, bit 56 - Signals the reporting of UCR errors in this MC bank. See Section 15.6.2
for additional detail.
•
AR (Action Required) flag, bit 55 - Indicates (when set) that MCA error code specific recovery
action must be performed by system software at the time this error was signaled. See Section
15.6.2 for additional detail.
•
•
If the UC bit (Figure 15-6) is 1, bits 54:53 are undefined.
If the UC bit (Figure 15-6) is 0, bits 54:53 indicate the status of the hardware structure that
reported the threshold-based error. See Table 15-1.
Table 15-1. Bits 54:53 in IA32_MCi_STATUS MSRs when IA32_MCG_CAP[11] = 1 and UC = 0
Bits 54:53
Meaning
00
No tracking - No hardware status tracking is provided for the structure reporting this event.
01
Green - Status tracking is provided for the structure posting the event; the current status is green (below threshold).
For more information, see Section 15.4, “Enhanced Cache Error reporting”.
10
Yellow - Status tracking is provided for the structure posting the event; the current status is yellow (above threshold).
For more information, see Section 15.4, “Enhanced Cache Error reporting”.
11
Reserved
Vol. 3B 15-7
MACHINE-CHECK ARCHITECTURE
•
PCC (processor context corrupt) flag, bit 57 — Indicates (when set) that the state of the processor might
have been corrupted by the error condition detected and that reliable restarting of the processor may not be
possible. When clear, this flag indicates that the error did not affect the processor’s state, and software may be
able to restart. When system software supports recovery, consult Section 15.10.4, “Machine-Check Software
Handler Guidelines for Error Recovery” for additional rules that apply.
•
ADDRV (IA32_MCi_ADDR register valid) flag, bit 58 — Indicates (when set) that the IA32_MCi_ADDR
register contains the address where the error occurred (see Section 15.3.2.3, “IA32_MCi_ADDR MSRs”). When
clear, this flag indicates that the IA32_MCi_ADDR register is either not implemented or does not contain the
address where the error occurred. Do not read these registers if they are not implemented in the processor.
•
MISCV (IA32_MCi_MISC register valid) flag, bit 59 — Indicates (when set) that the IA32_MCi_MISC
register contains additional information regarding the error. When clear, this flag indicates that the
IA32_MCi_MISC register is either not implemented or does not contain additional information regarding the
error. Do not read these registers if they are not implemented in the processor.
•
EN (error enabled) flag, bit 60 — Indicates (when set) that the error was enabled by the associated EEj bit
of the IA32_MCi_CTL register.
•
UC (error uncorrected) flag, bit 61 — Indicates (when set) that the processor did not or was not able to
correct the error condition. When clear, this flag indicates that the processor was able to correct the error
condition.
•
OVER (machine check overflow) flag, bit 62 — Indicates (when set) that a machine-check error occurred
while the results of a previous error were still in the error-reporting register bank (that is, the VAL bit was
already set in the IA32_MCi_STATUS register). The processor sets the OVER flag and software is responsible for
clearing it. In general, enabled errors are written over disabled errors, and uncorrected errors are written over
corrected errors. Uncorrected errors are not written over previous valid uncorrected errors. When
MCG_CMCI_P is set, corrected errors may not set the OVER flag. Software can rely on corrected error count in
IA32_MCi_Status[52:38] to determine if any additional corrected errors may have occurred. For more information, see Section 15.3.2.2.1, “Overwrite Rules for Machine Check Overflow”.
•
VAL (IA32_MCi_STATUS register valid) flag, bit 63 — Indicates (when set) that the information within the
IA32_MCi_STATUS register is valid. When this flag is set, the processor follows the rules given for the OVER flag
in the IA32_MCi_STATUS register when overwriting previously valid entries. The processor sets the VAL flag
and software is responsible for clearing it.
15.3.2.2.1 Overwrite Rules for Machine Check Overflow
Table 15-2 shows the overwrite rules for how to treat a second event if the cache has already posted an event to
the MC bank – that is, what to do if the valid bit for an MC bank already is set to 1. When more than one structure
posts events in a given bank, these rules specify whether a new event will overwrite a previous posting or not.
These rules define a priority for uncorrected (highest priority), yellow, and green/unmonitored (lowest priority)
status.
In Table 15-2, the values in the two left-most columns are IA32_MCi_STATUS[54:53].
Table 15-2. Overwrite Rules for Enabled Errors
First Event
Second Event
UC bit
Color
MCA Info
00/green
00/green
0
00/green
either
00/green
yellow
0
yellow
second error
yellow
00/green
0
yellow
first error
yellow
yellow
0
yellow
either
00/green/yellow
UC
1
undefined
second
UC
00/green/yellow
1
undefined
first
If a second event overwrites a previously posted event, the information (as guarded by individual valid bits) in the
MCi bank is entirely from the second event. Similarly, if a first event is retained, all of the information previously
posted for that event is retained. In general, when the logged error or the recent error is a corrected error, the
OVER bit (MCi_Status[62]) may be set to indicate an overflow. When MCG_CMCI_P is set in IA32_MCG_CAP,
system software should consult IA32_MCi_STATUS[52:38] to determine if additional corrected errors may have
15-8 Vol. 3B
MACHINE-CHECK ARCHITECTURE
occurred. Software may re-read IA32_MCi_STATUS, IA32_MCi_ADDR and IA32_MCi_MISC appropriately to ensure
data collected represent the last error logged.
After software polls a posting and clears the register, the valid bit is no longer set and therefore the meaning of the
rest of the bits, including the yellow/green/00 status field in bits 54:53, is undefined. The yellow/green indication
will only be posted for events associated with monitored structures – otherwise the unmonitored (00) code will be
posted in IA32_MCi_STATUS[54:53].
15.3.2.3
IA32_MCi_ADDR MSRs
The IA32_MCi_ADDR MSR contains the address of the code or data memory location that produced the machinecheck error if the ADDRV flag in the IA32_MCi_STATUS register is set (see Section 15-7, “IA32_MCi_ADDR MSR”).
The IA32_MCi_ADDR register is either not implemented or contains no address if the ADDRV flag in the
IA32_MCi_STATUS register is clear. When not implemented in the processor, all reads and writes to this MSR will
cause a general protection exception.
The address returned is an offset into a segment, linear address, or physical address. This depends on the error
encountered. When these registers are implemented, these registers can be cleared by explicitly writing 0s to
these registers. Writing 1s to these registers will cause a general-protection exception. See Figure 15-7.
Processor Without Support For Intel 64 Architecture
63
0
36 35
Address
Reserved
Processor With Support for Intel 64 Architecture
63
0
Address*
* Useful bits in this field depend on the address methodology in use when the
the register state is saved.
Figure 15-7. IA32_MCi_ADDR MSR
15.3.2.4
IA32_MCi_MISC MSRs
The IA32_MCi_MISC MSR contains additional information describing the machine-check error if the MISCV flag in
the IA32_MCi_STATUS register is set. The IA32_MCi_MISC_MSR is either not implemented or does not contain
additional information if the MISCV flag in the IA32_MCi_STATUS register is clear.
When not implemented in the processor, all reads and writes to this MSR will cause a general protection exception.
When implemented in a processor, these registers can be cleared by explicitly writing all 0s to them; writing 1s to
them causes a general-protection exception to be generated. This register is not implemented in any of the errorreporting register banks for the P6 or Intel Atom family processors.
If both MISCV and IA32_MCG_CAP[24] are set, the IA32_MCi_MISC_MSR is defined according to Figure 15-8 to
support software recovery of uncorrected errors (see Section 15.6):
Vol. 3B 15-9
MACHINE-CHECK ARCHITECTURE
9 8
63
6 5
0
Model Specific Information
Address Mode
Recoverable Address LSB
Figure 15-8. UCR Support in IA32_MCi_MISC Register
•
Recoverable Address LSB (bits 5:0): The lowest valid recoverable address bit. Indicates the position of the least
significant bit (LSB) of the recoverable error address. For example, if the processor logs bits [43:9] of the
address, the LSB sub-field in IA32_MCi_MISC is 01001b (9 decimal). For this example, bits [8:0] of the
recoverable error address in IA32_MCi_ADDR should be ignored.
•
Address Mode (bits 8:6): Address mode for the address logged in IA32_MCi_ADDR. The supported address
modes are given in Table 15-3.
Table 15-3. Address Mode in IA32_MCi_MISC[8:6]
IA32_MCi_MISC[8:6] Encoding
000
Segment Offset
001
Linear Address
010
Physical Address
011
Memory Address
100 to 110
111
•
Definition
Reserved
Generic
Model Specific Information (bits 63:9): Not architecturally defined.
15.3.2.5
IA32_MCi_CTL2 MSRs
The IA32_MCi_CTL2 MSR provides the programming interface to use corrected MC error signaling capability that is
indicated by IA32_MCG_CAP[10] = 1. Software must check for the presence of IA32_MCi_CTL2 on a per-bank
basis.
When IA32_MCG_CAP[10] = 1, the IA32_MCi_CTL2 MSR for each bank exists, i.e. reads and writes to these MSR
are supported. However, signaling interface for corrected MC errors may not be supported in all banks.
The layout of IA32_MCi_CTL2 is shown in Figure 15-9:
63
31 30 29
Reserved
15 14
Reserved
CMCI_EN—Enable/disable CMCI
Corrected error count threshold
Figure 15-9. IA32_MCi_CTL2 Register
15-10 Vol. 3B
0
MACHINE-CHECK ARCHITECTURE
•
Corrected error count threshold, bits 14:0 — Software must initialize this field. The value is compared with
the corrected error count field in IA32_MCi_STATUS, bits 38 through 52. An overflow event is signaled to the
CMCI LVT entry (see Table 10-1) in the APIC when the count value equals the threshold value. The new LVT
entry in the APIC is at 02F0H offset from the APIC_BASE. If CMCI interface is not supported for a particular
bank (but IA32_MCG_CAP[10] = 1), this field will always read 0.
•
CMCI_EN (Corrected error interrupt enable/disable/indicator), bits 30 — Software sets this bit to
enable the generation of corrected machine-check error interrupt (CMCI). If CMCI interface is not supported for
a particular bank (but IA32_MCG_CAP[10] = 1), this bit is writeable but will always return 0 for that bank. This
bit also indicates CMCI is supported or not supported in the corresponding bank. See Section 15.5 for details of
software detection of CMCI facility.
Some microarchitectural sub-systems that are the source of corrected MC errors may be shared by more than one
logical processors. Consequently, the facilities for reporting MC errors and controlling mechanisms may be shared
by more than one logical processors. For example, the IA32_MCi_CTL2 MSR is shared between logical processors
sharing a processor core. Software is responsible to program IA32_MCi_CTL2 MSR in a consistent manner with
CMCI delivery and usage.
After processor reset, IA32_MCi_CTL2 MSRs are zero’ed.
15.3.2.6
IA32_MCG Extended Machine Check State MSRs
The Pentium 4 and Intel Xeon processors implement a variable number of extended machine-check state MSRs.
The MCG_EXT_P flag in the IA32_MCG_CAP MSR indicates the presence of these extended registers, and the
MCG_EXT_CNT field indicates the number of these registers actually implemented. See Section 15.3.1.1,
“IA32_MCG_CAP MSR.” Also see Table 15-4.
Table 15-4. Extended Machine Check State MSRs
in Processors Without Support for Intel 64 Architecture
MSR
Address
Description
IA32_MCG_EAX
180H
Contains state of the EAX register at the time of the machine-check error.
IA32_MCG_EBX
181H
Contains state of the EBX register at the time of the machine-check error.
IA32_MCG_ECX
182H
Contains state of the ECX register at the time of the machine-check error.
IA32_MCG_EDX
183H
Contains state of the EDX register at the time of the machine-check error.
IA32_MCG_ESI
184H
Contains state of the ESI register at the time of the machine-check error.
IA32_MCG_EDI
185H
Contains state of the EDI register at the time of the machine-check error.
IA32_MCG_EBP
186H
Contains state of the EBP register at the time of the machine-check error.
IA32_MCG_ESP
187H
Contains state of the ESP register at the time of the machine-check error.
IA32_MCG_EFLAGS
188H
Contains state of the EFLAGS register at the time of the machine-check error.
IA32_MCG_EIP
189H
Contains state of the EIP register at the time of the machine-check error.
IA32_MCG_MISC
18AH
When set, indicates that a page assist or page fault occurred during DS normal
operation.
In processors with support for Intel 64 architecture, 64-bit machine check state MSRs are aliased to the legacy
MSRs. In addition, there may be registers beyond IA32_MCG_MISC. These may include up to five reserved MSRs
(IA32_MCG_RESERVED[1:5]) and save-state MSRs for registers introduced in 64-bit mode. See Table 15-5.
Table 15-5. Extended Machine Check State MSRs
In Processors With Support For Intel 64 Architecture
MSR
Address
Description
IA32_MCG_RAX
180H
Contains state of the RAX register at the time of the machine-check error.
IA32_MCG_RBX
181H
Contains state of the RBX register at the time of the machine-check error.
Vol. 3B 15-11
MACHINE-CHECK ARCHITECTURE
Table 15-5. Extended Machine Check State MSRs
In Processors With Support For Intel 64 Architecture (Contd.)
MSR
Address
Description
IA32_MCG_RCX
182H
Contains state of the RCX register at the time of the machine-check error.
IA32_MCG_RDX
183H
Contains state of the RDX register at the time of the machine-check error.
IA32_MCG_RSI
184H
Contains state of the RSI register at the time of the machine-check error.
IA32_MCG_RDI
185H
Contains state of the RDI register at the time of the machine-check error.
IA32_MCG_RBP
186H
Contains state of the RBP register at the time of the machine-check error.
IA32_MCG_RSP
187H
Contains state of the RSP register at the time of the machine-check error.
IA32_MCG_RFLAGS
188H
Contains state of the RFLAGS register at the time of the machine-check error.
IA32_MCG_RIP
189H
Contains state of the RIP register at the time of the machine-check error.
IA32_MCG_MISC
18AH
When set, indicates that a page assist or page fault occurred during DS normal
operation.
IA32_MCG_
RSERVED[1:5]
18BH18FH
These registers, if present, are reserved.
IA32_MCG_R8
190H
Contains state of the R8 register at the time of the machine-check error.
IA32_MCG_R9
191H
Contains state of the R9 register at the time of the machine-check error.
IA32_MCG_R10
192H
Contains state of the R10 register at the time of the machine-check error.
IA32_MCG_R11
193H
Contains state of the R11 register at the time of the machine-check error.
IA32_MCG_R12
194H
Contains state of the R12 register at the time of the machine-check error.
IA32_MCG_R13
195H
Contains state of the R13 register at the time of the machine-check error.
IA32_MCG_R14
196H
Contains state of the R14 register at the time of the machine-check error.
IA32_MCG_R15
197H
Contains state of the R15 register at the time of the machine-check error.
When a machine-check error is detected on a Pentium 4 or Intel Xeon processor, the processor saves the state of
the general-purpose registers, the R/EFLAGS register, and the R/EIP in these extended machine-check state MSRs.
This information can be used by a debugger to analyze the error.
These registers are read/write to zero registers. This means software can read them; but if software writes to
them, only all zeros is allowed. If software attempts to write a non-zero value into one of these registers, a generalprotection (#GP) exception is generated. These registers are cleared on a hardware reset (power-up or RESET),
but maintain their contents following a soft reset (INIT reset).
15.3.3
Mapping of the Pentium Processor Machine-Check Errors
to the Machine-Check Architecture
The Pentium processor reports machine-check errors using two registers: P5_MC_TYPE and P5_MC_ADDR. The
Pentium 4, Intel Xeon, Intel Atom, and P6 family processors map these registers to the IA32_MCi_STATUS and
IA32_MCi_ADDR in the error-reporting register bank. This bank reports on the same type of external bus errors
reported in P5_MC_TYPE and P5_MC_ADDR.
The information in these registers can then be accessed in two ways:
•
By reading the IA32_MCi_STATUS and IA32_MCi_ADDR registers as part of a general machine-check exception
handler written for Pentium 4, Intel Atom and P6 family processors.
•
By reading the P5_MC_TYPE and P5_MC_ADDR registers using the RDMSR instruction.
The second capability permits a machine-check exception handler written to run on a Pentium processor to be run
on a Pentium 4, Intel Xeon, Intel Atom, or P6 family processor. There is a limitation in that information returned by
the Pentium 4, Intel Xeon, Intel Atom, and P6 family processors is encoded differently than information returned
by the Pentium processor. To run a Pentium processor machine-check exception handler on a Pentium 4, Intel
Xeon, Intel Atom, or P6 family processor; the handler must be written to interpret P5_MC_TYPE encodings
correctly.
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MACHINE-CHECK ARCHITECTURE
15.4
ENHANCED CACHE ERROR REPORTING
Starting with Intel Core Duo processors, cache error reporting was enhanced. In earlier Intel processors, cache
status was based on the number of correction events that occurred in a cache. In the new paradigm, called
“threshold-based error status”, cache status is based on the number of lines (ECC blocks) in a cache that incur
repeated corrections. The threshold is chosen by Intel, based on various factors. If a processor supports thresholdbased error status, it sets IA32_MCG_CAP[11] (MCG_TES_P) to 1; if not, to 0.
A processor that supports enhanced cache error reporting contains hardware that tracks the operating status of
certain caches and provides an indicator of their “health”. The hardware reports a “green” status when the number
of lines that incur repeated corrections is at or below a pre-defined threshold, and a “yellow” status when the
number of affected lines exceeds the threshold. Yellow status means that the cache reporting the event is operating correctly, but you should schedule the system for servicing within a few weeks.
Intel recommends that you rely on this mechanism for structures supported by threshold-base error reporting.
The CPU/system/platform response to a yellow event should be less severe than its response to an uncorrected
error. An uncorrected error means that a serious error has actually occurred, whereas the yellow condition is a
warning that the number of affected lines has exceeded the threshold but is not, in itself, a serious event: the error
was corrected and system state was not compromised.
The green/yellow status indicator is not a foolproof early warning for an uncorrected error resulting from the failure
of two bits in the same ECC block. Such a failure can occur and cause an uncorrected error before the yellow
threshold is reached. However, the chance of an uncorrected error increases as the number of affected lines
increases.
15.5
CORRECTED MACHINE CHECK ERROR INTERRUPT
Corrected machine-check error interrupt (CMCI) is an architectural enhancement to the machine-check architecture. It provides capabilities beyond those of threshold-based error reporting (Section 15.4). With threshold-based
error reporting, software is limited to use periodic polling to query the status of hardware corrected MC errors.
CMCI provides a signaling mechanism to deliver a local interrupt based on threshold values that software can
program using the IA32_MCi_CTL2 MSRs.
CMCI is disabled by default. System software is required to enable CMCI for each IA32_MCi bank that support the
reporting of hardware corrected errors if IA32_MCG_CAP[10] = 1.
System software use IA32_MCi_CTL2 MSR to enable/disable the CMCI capability for each bank and program
threshold values into IA32_MCi_CTL2 MSR. CMCI is not affected by the CR4.MCE bit, and it is not affected by the
IA32_MCi_CTL MSRs.
To detect the existence of thresholding for a given bank, software writes only bits 14:0 with the threshold value. If
the bits persist, then thresholding is available (and CMCI is available). If the bits are all 0's, then no thresholding
exists. To detect that CMCI signaling exists, software writes a 1 to bit 30 of the MCi_CTL2 register. Upon subsequent read, if bit 30 = 0, no CMCI is available for this bank and no corrected or UCNA errors will be reported on this
bank. If bit 30 = 1, then CMCI is available and enabled.
15.5.1
CMCI Local APIC Interface
The operation of CMCI is depicted in Figure 15-10.
Vol. 3B 15-13
MACHINE-CHECK ARCHITECTURE
Software write 1 to enable
63
31 30 29
MCi_CTL2
Error threshold
?=
53 52
MCi_STATUS
0
14
Count overflow threshold -> CMCI LVT in local APIC
38 37
0
APIC_BASE + 2F0H
Error count
Figure 15-10. CMCI Behavior
CMCI interrupt delivery is configured by writing to the LVT CMCI register entry in the local APIC register space at
default address of APIC_BASE + 2F0H. A CMCI interrupt can be delivered to more than one logical processors if
multiple logical processors are affected by the associated MC errors. For example, if a corrected bit error in a cache
shared by two logical processors caused a CMCI, the interrupt will be delivered to both logical processors sharing
that microarchitectural sub-system. Similarly, package level errors may cause CMCI to be delivered to all logical
processors within the package. However, system level errors will not be handled by CMCI.
See Section 10.5.1, “Local Vector Table” for details regarding the LVT CMCI register.
15.5.2
System Software Recommendation for Managing CMCI and Machine Check Resources
System software must enable and manage CMCI, set up interrupt handlers to service CMCI interrupts delivered to
affected logical processors, program CMCI LVT entry, and query machine check banks that are shared by more than
one logical processors.
This section describes techniques system software can implement to manage CMCI initialization, service CMCI
interrupts in a efficient manner to minimize contentions to access shared MSR resources.
15.5.2.1
CMCI Initialization
Although a CMCI interrupt may be delivered to more than one logical processors depending on the nature of the
corrected MC error, only one instance of the interrupt service routine needs to perform the necessary service and
make queries to the machine-check banks. The following steps describes a technique that limits the amount of
work the system has to do in response to a CMCI.
•
To provide maximum flexibility, system software should define per-thread data structure for each logical
processor to allow equal-opportunity and efficient response to interrupt delivery. Specifically, the per-thread
data structure should include a set of per-bank fields to track which machine check bank it needs to access in
response to a delivered CMCI interrupt. The number of banks that needs to be tracked is determined by
IA32_MCG_CAP[7:0].
•
Initialization of per-thread data structure. The initialization of per-thread data structure must be done serially
on each logical processor in the system. The sequencing order to start the per-thread initialization between
different logical processor is arbitrary. But it must observe the following specific detail to satisfy the shared
nature of specific MSR resources:
a. Each thread initializes its data structure to indicate that it does not own any MC bank registers.
b. Each thread examines IA32_MCi_CTL2[30] indicator for each bank to determine if another thread has
already claimed ownership of that bank.
•
If IA32_MCi_CTL2[30] had been set by another thread. This thread can not own bank i and should
proceed to step b. and examine the next machine check bank until all of the machine check banks are
exhausted.
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MACHINE-CHECK ARCHITECTURE
•
c.
•
If IA32_MCi_CTL2[30] = 0, proceed to step c.
Check whether writing a 1 into IA32_MCi_CTL2[30] can return with 1 on a subsequent read to determine
this bank can support CMCI.
•
If IA32_MCi_CTL2[30] = 0, this bank does not support CMCI. This thread can not own bank i and should
proceed to step b. and examine the next machine check bank until all of the machine check banks are
exhausted.
•
If IA32_MCi_CTL2[30] = 1, modify the per-thread data structure to indicate this thread claims
ownership to the MC bank; proceed to initialize the error threshold count (bits 15:0) of that bank as
described in Chapter 15, “CMCI Threshold Management”. Then proceed to step b. and examine the next
machine check bank until all of the machine check banks are exhausted.
After the thread has examined all of the machine check banks, it sees if it owns any MC banks to service CMCI.
If any bank has been claimed by this thread:
— Ensure that the CMCI interrupt handler has been set up as described in Chapter 15, “CMCI Interrupt
Handler”.
— Initialize the CMCI LVT entry, as described in Section 15.5.1, “CMCI Local APIC Interface”.
— Log and clear all of IA32_MCi_Status registers for the banks that this thread owns. This will allow new
errors to be logged.
15.5.2.2
CMCI Threshold Management
The Corrected MC error threshold field, IA32_MCi_CTL2[15:0], is architecturally defined. Specifically, all these bits
are writable by software, but different processor implementations may choose to implement less than 15 bits as
threshold for the overflow comparison with IA32_MCi_STATUS[52:38]. The following describes techniques that
software can manage CMCI threshold to be compatible with changes in implementation characteristics:
•
Software can set the initial threshold value to 1 by writing 1 to IA32_MCi_CTL2[15:0]. This will cause overflow
condition on every corrected MC error and generates a CMCI interrupt.
•
To increase the threshold and reduce the frequency of CMCI servicing:
a. Find the maximum threshold value a given processor implementation supports. The steps are:
•
•
Write 7FFFH to IA32_MCi_CTL2[15:0],
Read back IA32_MCi_CTL2[15:0], the lower 15 bits (14:0) is the maximum threshold supported by the
processor.
b. Increase the threshold to a value below the maximum value discovered using step a.
15.5.2.3
CMCI Interrupt Handler
The following describes techniques system software may consider to implement a CMCI service routine:
•
The service routine examines its private per-thread data structure to check which set of MC banks it has
ownership. If the thread does not have ownership of a given MC bank, proceed to the next MC bank. Ownership
is determined at initialization time which is described in Section [Cross Reference to 14.5.2.1].
If the thread had claimed ownership to an MC bank, this technique will allow each logical processors to handle
corrected MC errors independently and requires no synchronization to access shared MSR resources. Consult
Example 15-5 for guidelines on logging when processing CMCI.
15.6
RECOVERY OF UNCORRECTED RECOVERABLE (UCR) ERRORS
Recovery of uncorrected recoverable machine check errors is an enhancement in machine-check architecture. The
first processor that supports this feature is 45 nm Intel 64 processor on which CPUID reports
DisplayFamily_DisplayModel as 06H_2EH (see CPUID instruction in Chapter 3, “Instruction Set Reference, A-M” in
the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 2A). This allow system software to
perform recovery action on certain class of uncorrected errors and continue execution.
Vol. 3B 15-15
MACHINE-CHECK ARCHITECTURE
15.6.1
Detection of Software Error Recovery Support
Software must use bit 24 of IA32_MCG_CAP (MCG_SER_P) to detect the presence of software error recovery
support (see Figure 15-2). When IA32_MCG_CAP[24] is set, this indicates that the processor supports software
error recovery. When this bit is clear, this indicates that there is no support for error recovery from the processor
and the primary responsibility of the machine check handler is logging the machine check error information and
shutting down the system.
The new class of architectural MCA errors from which system software can attempt recovery is called Uncorrected
Recoverable (UCR) Errors. UCR errors are uncorrected errors that have been detected and signaled but have not
corrupted the processor context. For certain UCR errors, this means that once system software has performed a
certain recovery action, it is possible to continue execution on this processor. UCR error reporting provides an error
containment mechanism for data poisoning. The machine check handler will use the error log information from the
error reporting registers to analyze and implement specific error recovery actions for UCR errors.
15.6.2
UCR Error Reporting and Logging
IA32_MCi_STATUS MSR is used for reporting UCR errors and existing corrected or uncorrected errors. The definitions of IA32_MCi_STATUS, including bit fields to identify UCR errors, is shown in Figure 15-6. UCR errors can be
signaled through either the corrected machine check interrupt (CMCI) or machine check exception (MCE) path
depending on the type of the UCR error.
When IA32_MCG_CAP[24] is set, a UCR error is indicated by the following bit settings in the IA32_MCi_STATUS
register:
•
•
•
Valid (bit 63) = 1
UC (bit 61) = 1
PCC (bit 57) = 0
Additional information from the IA32_MCi_MISC and the IA32_MCi_ADDR registers for the UCR error are available
when the ADDRV and the MISCV flags in the IA32_MCi_STATUS register are set (see Section 15.3.2.4). The MCA
error code field of the IA32_MCi_STATUS register indicates the type of UCR error. System software can interpret
the MCA error code field to analyze and identify the necessary recovery action for the given UCR error.
In addition, the IA32_MCi_STATUS register bit fields, bits 56:55, are defined (see Figure 15-6) to provide additional information to help system software to properly identify the necessary recovery action for the UCR error:
•
S (Signaling) flag, bit 56 - Indicates (when set) that a machine check exception was generated for the UCR
error reported in this MC bank and system software needs to check the AR flag and the MCA error code fields in
the IA32_MCi_STATUS register to identify the necessary recovery action for this error. When the S flag in the
IA32_MCi_STATUS register is clear, this UCR error was not signaled via a machine check exception and instead
was reported as a corrected machine check (CMC). System software is not required to take any recovery action
when the S flag in the IA32_MCi_STATUS register is clear.
•
AR (Action Required) flag, bit 55 - Indicates (when set) that MCA error code specific recovery action must be
performed by system software at the time this error was signaled. This recovery action must be completed
successfully before any additional work is scheduled for this processor. When the RIPV flag in the
IA32_MCG_STATUS is clear, an alternative execution stream needs to be provided; when the MCA error code
specific recovery specific recovery action cannot be successfully completed, system software must shut down
the system. When the AR flag in the IA32_MCi_STATUS register is clear, system software may still take MCA
error code specific recovery action but this is optional; system software can safely resume program execution
at the instruction pointer saved on the stack from the machine check exception when the RIPV flag in the
IA32_MCG_STATUS register is set.
Both the S and the AR flags in the IA32_MCi_STATUS register are defined to be sticky bits, which mean that once
set, the processor does not clear them. Only software and good power-on reset can clear the S and the AR-flags.
Both the S and the AR flags are only set when the processor reports the UCR errors (MCG_CAP[24] is set).
15.6.3
UCR Error Classification
With the S and AR flag encoding in the IA32_MCi_STATUS register, UCR errors can be classified as:
15-16 Vol. 3B
MACHINE-CHECK ARCHITECTURE
•
Uncorrected no action required (UCNA) - is a UCR error that is not signaled via a machine check exception and,
instead, is reported to system software as a corrected machine check error. UCNA errors indicate that some
data in the system is corrupted, but the data has not been consumed and the processor state is valid and you
may continue execution on this processor. UCNA errors require no action from system software to continue
execution. A UNCA error is indicated with UC=1, PCC=0, S=0 and AR=0 in the IA32_MCi_STATUS register.
•
Software recoverable action optional (SRAO) - a UCR error is signaled either via a machine check exception or
CMCI. System software recovery action is optional and not required to continue execution from this machine
check exception. SRAO errors indicate that some data in the system is corrupt, but the data has not been
consumed and the processor state is valid. SRAO errors provide the additional error information for system
software to perform a recovery action. An SRAO error when signaled as a machine check is indicated with
UC=1, PCC=0, S=1, EN=1 and AR=0 in the IA32_MCi_STATUS register. In cases when SRAO is signaled via
CMCI the error signature is indicated via UC=1, PCC=0, S=0. Recovery actions for SRAO errors are MCA error
code specific. The MISCV and the ADDRV flags in the IA32_MCi_STATUS register are set when the additional
error information is available from the IA32_MCi_MISC and the IA32_MCi_ADDR registers. System software
needs to inspect the MCA error code fields in the IA32_MCi_STATUS register to identify the specific recovery
action for a given SRAO error. If MISCV and ADDRV are not set, it is recommended that no system software
error recovery be performed however, system software can resume execution.
•
Software recoverable action required (SRAR) - a UCR error that requires system software to take a recovery
action on this processor before scheduling another stream of execution on this processor. SRAR errors indicate
that the error was detected and raised at the point of the consumption in the execution flow. An SRAR error is
indicated with UC=1, PCC=0, S=1, EN=1 and AR=1 in the IA32_MCi_STATUS register. Recovery actions are
MCA error code specific. The MISCV and the ADDRV flags in the IA32_MCi_STATUS register are set when the
additional error information is available from the IA32_MCi_MISC and the IA32_MCi_ADDR registers. System
software needs to inspect the MCA error code fields in the IA32_MCi_STATUS register to identify the specific
recovery action for a given SRAR error. If MISCV and ADDRV are not set, it is recommended that system
software shutdown the system.
Table 15-6 summarizes UCR, corrected, and uncorrected errors.
Table 15-6. MC Error Classifications
Type of Error1
UC
EN
PCC
S
AR
Signaling Software Action
Uncorrected Error (UC)
1
1
1
x
x
MCE
If EN=1, reset the system, else log
and OK to keep the system running.
SRAR
1
1
0
1
1
MCE
For known MCACOD, take specific
recovery action;
Example
Cache to processor load
error.
For unknown MCACOD, must
bugcheck.
If OVER=1, reset system, else take
specific recovery action.
SRAO
1
x2
0
x2 0
MCE/CMC
For known MCACOD, take specific
recovery action;
Patrol scrub and explicit
writeback poison errors.
For unknown MCACOD, OK to keep
the system running.
UCNA
1
x
0
0
0
CMC
Log the error and Ok to keep the
system running.
Poison detection error.
Corrected Error (CE)
0
x
x
x
x
CMC
Log the error and no corrective
action required.
ECC in caches and
memory.
NOTES:
1. SRAR, SRAO and UCNA errors are supported by the processor only when IA32_MCG_CAP[24] (MCG_SER_P) is set.
2. EN=1, S=1 when signaled via MCE. EN=x, S=0 when signaled via CMC.
15.6.4
UCR Error Overwrite Rules
In general, the overwrite rules are as follows:
Vol. 3B 15-17
MACHINE-CHECK ARCHITECTURE
•
•
•
•
UCR errors will overwrite corrected errors.
Uncorrected (PCC=1) errors overwrite UCR (PCC=0) errors.
UCR errors are not written over previous UCR errors.
Corrected errors do not write over previous UCR errors.
Regardless of whether the 1st error is retained or the 2nd error is overwritten over the 1st error, the OVER flag in
the IA32_MCi_STATUS register will be set to indicate an overflow condition. As the S flag and AR flag in the
IA32_MCi_STATUS register are defined to be sticky flags, a second event cannot clear these 2 flags once set,
however the MC bank information may be filled in for the 2nd error. The table below shows the overwrite rules and
how to treat a second error if the first event is already logged in a MC bank along with the resulting bit setting of
the UC, PCC, and AR flags in the IA32_MCi_STATUS register. As UCNA and SRA0 errors do not require recovery
action from system software to continue program execution, a system reset by system software is not required
unless the AR flag or PCC flag is set for the UCR overflow case (OVER=1, VAL=1, UC=1, PCC=0).
Table 15-7 lists overwrite rules for uncorrected errors, corrected errors, and uncorrected recoverable errors.
Table 15-7. Overwrite Rules for UC, CE, and UCR Errors
First Event
Second Event
UC
PCC
S
CE
UCR
1
0
UCR
CE
1
0
UCNA
UCNA
1
UCNA
SRAO
UCNA
SRAO
MCA Bank
Reset System
0 if UCNA, else 1 1 if SRAR, else 0
second
yes, if AR=1
0 if UCNA, else 1 1 if SRAR, else 0
first
yes, if AR=1
0
0
0
first
no
1
0
1
0
first
no
SRAR
1
0
1
1
first
yes
UCNA
1
0
1
0
first
no
SRAO
SRAO
1
0
1
0
first
no
SRAO
SRAR
1
0
1
1
first
yes
SRAR
UCNA
1
0
1
1
first
yes
SRAR
SRAO
1
0
1
1
first
yes
SRAR
SRAR
1
0
1
1
first
yes
UCR
UC
1
1
undefined
undefined
second
yes
UC
UCR
1
1
undefined
undefined
first
yes
15.7
AR
MACHINE-CHECK AVAILABILITY
The machine-check architecture and machine-check exception (#MC) are model-specific features. Software can
execute the CPUID instruction to determine whether a processor implements these features. Following the execution of the CPUID instruction, the settings of the MCA flag (bit 14) and MCE flag (bit 7) in EDX indicate whether the
processor implements the machine-check architecture and machine-check exception.
15.8
MACHINE-CHECK INITIALIZATION
To use the processors machine-check architecture, software must initialize the processor to activate the machinecheck exception and the error-reporting mechanism.
Example 15-1 gives pseudocode for performing this initialization. This pseudocode checks for the existence of the
machine-check architecture and exception; it then enables machine-check exception and the error-reporting
register banks. The pseudocode shown is compatible with the Pentium 4, Intel Xeon, Intel Atom, P6 family, and
Pentium processors.
Following power up or power cycling, IA32_MCi_STATUS registers are not guaranteed to have valid data until after
they are initially cleared to zero by software (as shown in the initialization pseudocode in Example 15-1). In addition, when using P6 family processors, software must set MCi_STATUS registers to zero when doing a soft-reset.
15-18 Vol. 3B
MACHINE-CHECK ARCHITECTURE
Example 15-1. Machine-Check Initialization Pseudocode
Check CPUID Feature Flags for MCE and MCA support
IF CPU supports MCE
THEN
IF CPU supports MCA
THEN
IF (IA32_MCG_CAP.MCG_CTL_P = 1)
(* IA32_MCG_CTL register is present *)
THEN
IA32_MCG_CTL ← FFFFFFFFFFFFFFFFH;
(* enables all MCA features *)
FI
IF (IA32_MCG_CAP.MCG_LMCE_P = 1 and IA32_FEATURE_CONTROL.LOCK = 1 and IA32_FEATURE_CONTROL.LMCE_ON= 1)
(* IA32_MCG_EXT_CTL register is present and platform has enabled LMCE to permit system software to use LMCE *)
THEN
IA32_MCG_EXT_CTL ← IA32_MCG_EXT_CTL | 01H;
(* System software enables LMCE capability for hardware to signal MCE to a single logical processor*)
FI
(* Determine number of error-reporting banks supported *)
COUNT← IA32_MCG_CAP.Count;
MAX_BANK_NUMBER ← COUNT - 1;
IF (Processor Family is 6H and Processor EXTMODEL:MODEL is less than 1AH)
THEN
(* Enable logging of all errors except for MC0_CTL register *)
FOR error-reporting banks (1 through MAX_BANK_NUMBER)
DO
IA32_MCi_CTL ← 0FFFFFFFFFFFFFFFFH;
OD
ELSE
(* Enable logging of all errors including MC0_CTL register *)
FOR error-reporting banks (0 through MAX_BANK_NUMBER)
DO
IA32_MCi_CTL ← 0FFFFFFFFFFFFFFFFH;
OD
FI
(* BIOS clears all errors only on power-on reset *)
IF (BIOS detects Power-on reset)
THEN
FOR error-reporting banks (0 through MAX_BANK_NUMBER)
DO
IA32_MCi_STATUS ← 0;
OD
ELSE
FOR error-reporting banks (0 through MAX_BANK_NUMBER)
DO
(Optional for BIOS and OS) Log valid errors
(OS only) IA32_MCi_STATUS ← 0;
OD
FI
FI
Setup the Machine Check Exception (#MC) handler for vector 18 in IDT
Set the MCE bit (bit 6) in CR4 register to enable Machine-Check Exceptions
FI
Vol. 3B 15-19
MACHINE-CHECK ARCHITECTURE
15.9
INTERPRETING THE MCA ERROR CODES
When the processor detects a machine-check error condition, it writes a 16-bit error code to the MCA error code
field of one of the IA32_MCi_STATUS registers and sets the VAL (valid) flag in that register. The processor may also
write a 16-bit model-specific error code in the IA32_MCi_STATUS register depending on the implementation of the
machine-check architecture of the processor.
The MCA error codes are architecturally defined for Intel 64 and IA-32 processors. To determine the cause of a
machine-check exception, the machine-check exception handler must read the VAL flag for each
IA32_MCi_STATUS register. If the flag is set, the machine check-exception handler must then read the MCA error
code field of the register. It is the encoding of the MCA error code field [15:0] that determines the type of error
being reported and not the register bank reporting it.
There are two types of MCA error codes: simple error codes and compound error codes.
15.9.1
Simple Error Codes
Table 15-8 shows the simple error codes. These unique codes indicate global error information.
Table 15-8. IA32_MCi_Status [15:0] Simple Error Code Encoding
Error Code
Binary Encoding
Meaning
No Error
0000 0000 0000 0000
No error has been reported to this bank of error-reporting
registers.
Unclassified
0000 0000 0000 0001
This error has not been classified into the MCA error classes.
Microcode ROM Parity Error
0000 0000 0000 0010
Parity error in internal microcode ROM
External Error
0000 0000 0000 0011
The BINIT# from another processor caused this processor to
enter machine check.1
FRC Error
0000 0000 0000 0100
FRC (functional redundancy check) master/slave error
Internal Parity Error
0000 0000 0000 0101
Internal parity error.
SMM Handler Code Access
Violation
0000 0000 0000 0110
An attempt was made by the SMM Handler to execute
outside the ranges specified by SMRR.
Internal Timer Error
0000 0100 0000 0000
Internal timer error.
I/O Error
0000 1110 0000 1011
generic I/O error.
Internal Unclassified
0000 01xx xxxx xxxx
Internal unclassified errors. 2
NOTES:
1. BINIT# assertion will cause a machine check exception if the processor (or any processor on the same external bus) has BINIT#
observation enabled during power-on configuration (hardware strapping) and if machine check exceptions are enabled (by setting
CR4.MCE = 1).
2. At least one X must equal one. Internal unclassified errors have not been classified.
15.9.2
Compound Error Codes
Compound error codes describe errors related to the TLBs, memory, caches, bus and interconnect logic, and
internal timer. A set of sub-fields is common to all of compound errors. These sub-fields describe the type of access,
level in the cache hierarchy, and type of request. Table 15-9 shows the general form of the compound error codes.
Table 15-9. IA32_MCi_Status [15:0] Compound Error Code Encoding
Type
Form
Generic Cache Hierarchy
000F 0000 0000 11LL
Generic cache hierarchy error
TLB Errors
000F 0000 0001 TTLL
{TT}TLB{LL}_ERR
Memory Controller Errors
000F 0000 1MMM CCCC
{MMM}_CHANNEL{CCCC}_ERR
15-20 Vol. 3B
Interpretation
MACHINE-CHECK ARCHITECTURE
Table 15-9. IA32_MCi_Status [15:0] Compound Error Code Encoding (Contd.)
Cache Hierarchy Errors
000F 0001 RRRR TTLL
{TT}CACHE{LL}_{RRRR}_ERR
Bus and Interconnect Errors
000F 1PPT RRRR IILL
BUS{LL}_{PP}_{RRRR}_{II}_{T}_ERR
The “Interpretation” column in the table indicates the name of a compound error. The name is constructed by
substituting mnemonics for the sub-field names given within curly braces. For example, the error code
ICACHEL1_RD_ERR is constructed from the form:
{TT}CACHE{LL}_{RRRR}_ERR,
where {TT} is replaced by I, {LL} is replaced by L1, and {RRRR} is replaced by RD.
For more information on the “Form” and “Interpretation” columns, see Sections Section 15.9.2.1, “Correction
Report Filtering (F) Bit” through Section 15.9.2.5, “Bus and Interconnect Errors”.
15.9.2.1
Correction Report Filtering (F) Bit
Starting with Intel Core Duo processors, bit 12 in the “Form” column in Table 15-9 is used to indicate that a particular posting to a log may be the last posting for corrections in that line/entry, at least for some time:
•
•
0 in bit 12 indicates “normal” filtering (original P6/Pentium4/Atom/Xeon processor meaning).
1 in bit 12 indicates “corrected” filtering (filtering is activated for the line/entry in the posting). Filtering means
that some or all of the subsequent corrections to this entry (in this structure) will not be posted. The enhanced
error reporting introduced with the Intel Core Duo processors is based on tracking the lines affected by
repeated corrections (see Section 15.4, “Enhanced Cache Error reporting”). This capability is indicated by
IA32_MCG_CAP[11]. Only the first few correction events for a line are posted; subsequent redundant
correction events to the same line are not posted. Uncorrected events are always posted.
The behavior of error filtering after crossing the yellow threshold is model-specific. Filtering has meaning only for
corrected errors (UC=0 in IA32_MCi_STATUS MSR). System software must ignore filtering bit (12) for uncorrected
errors.
15.9.2.2
Transaction Type (TT) Sub-Field
The 2-bit TT sub-field (Table 15-10) indicates the type of transaction (data, instruction, or generic). The sub-field
applies to the TLB, cache, and interconnect error conditions. Note that interconnect error conditions are primarily
associated with P6 family and Pentium processors, which utilize an external APIC bus separate from the system
bus. The generic type is reported when the processor cannot determine the transaction type.
Table 15-10. Encoding for TT (Transaction Type) Sub-Field
Transaction Type
Mnemonic
Binary Encoding
Instruction
I
00
Data
D
01
Generic
G
10
15.9.2.3
Level (LL) Sub-Field
The 2-bit LL sub-field (see Table 15-11) indicates the level in the memory hierarchy where the error occurred (level
0, level 1, level 2, or generic). The LL sub-field also applies to the TLB, cache, and interconnect error conditions.
The Pentium 4, Intel Xeon, Intel Atom, and P6 family processors support two levels in the cache hierarchy and one
level in the TLBs. Again, the generic type is reported when the processor cannot determine the hierarchy level.
Table 15-11. Level Encoding for LL (Memory Hierarchy Level) Sub-Field
Hierarchy Level
Mnemonic
Binary Encoding
Level 0
L0
00
Level 1
L1
01
Vol. 3B 15-21
MACHINE-CHECK ARCHITECTURE
Table 15-11. Level Encoding for LL (Memory Hierarchy Level) Sub-Field (Contd.)
Level 2
L2
10
Generic
LG
11
15.9.2.4
Request (RRRR) Sub-Field
The 4-bit RRRR sub-field (see Table 15-12) indicates the type of action associated with the error. Actions include
read and write operations, prefetches, cache evictions, and snoops. Generic error is returned when the type of
error cannot be determined. Generic read and generic write are returned when the processor cannot determine the
type of instruction or data request that caused the error. Eviction and snoop requests apply only to the caches. All
of the other requests apply to TLBs, caches and interconnects.
Table 15-12. Encoding of Request (RRRR) Sub-Field
Request Type
Mnemonic
Generic Error
ERR
0000
Generic Read
RD
0001
Generic Write
WR
0010
Data Read
DRD
0011
Data Write
DWR
0100
Instruction Fetch
IRD
0101
Prefetch
PREFETCH
0110
Eviction
EVICT
0111
Snoop
SNOOP
1000
15.9.2.5
Binary Encoding
Bus and Interconnect Errors
The bus and interconnect errors are defined with the 2-bit PP (participation), 1-bit T (time-out), and 2-bit II
(memory or I/O) sub-fields, in addition to the LL and RRRR sub-fields (see Table 15-13). The bus error conditions
are implementation dependent and related to the type of bus implemented by the processor. Likewise, the interconnect error conditions are predicated on a specific implementation-dependent interconnect model that describes
the connections between the different levels of the storage hierarchy. The type of bus is implementation dependent, and as such is not specified in this document. A bus or interconnect transaction consists of a request involving
an address and a response.
Table 15-13. Encodings of PP, T, and II Sub-Fields
Sub-Field
Transaction
Mnemonic
PP (Participation)
Local processor* originated request
SRC
00
Local processor* responded to request
RES
01
Local processor* observed error as third party
OBS
10
Generic
T (Time-out)
II (Memory or I/O)
Binary Encoding
11
Request timed out
TIMEOUT
1
Request did not time out
NOTIMEOUT
0
Memory Access
M
00
Reserved
I/O
Other transaction
01
IO
10
11
NOTE:
* Local processor differentiates the processor reporting the error from other system components (including the APIC, other processors, etc.).
15-22 Vol. 3B
MACHINE-CHECK ARCHITECTURE
15.9.2.6
Memory Controller Errors
The memory controller errors are defined with the 3-bit MMM (memory transaction type), and 4-bit CCCC
(channel) sub-fields. The encodings for MMM and CCCC are defined in Table 15-14.
Table 15-14. Encodings of MMM and CCCC Sub-Fields
Sub-Field
Transaction
Mnemonic
Binary Encoding
MMM
Generic undefined request
GEN
000
Memory read error
RD
001
Memory write error
WR
010
Address/Command Error
AC
011
Memory Scrubbing Error
MS
100
Reserved
CCCC
101-111
Channel number
CHN
0000-1110
Channel not specified
15.9.3
1111
Architecturally Defined UCR Errors
Software recoverable compound error code are defined in this section.
15.9.3.1
Architecturally Defined SRAO Errors
The following two SRAO errors are architecturally defined.
•
•
UCR Errors detected by memory controller scrubbing; and
UCR Errors detected during L3 cache (L3) explicit writebacks.
The MCA error code encodings for these two architecturally-defined UCR errors corresponds to sub-classes of
compound MCA error codes (see Table 15-9). Their values and compound encoding format are given in Table
15-15.
Table 15-15. MCA Compound Error Code Encoding for SRAO Errors
Type
MCACOD Value
Memory Scrubbing
C0H - CFH
MCA Error Code Encoding1
0000_0000_1100_CCCC
000F 0000 1MMM CCCC (Memory Controller Error), where
Memory subfield MMM = 100B (memory scrubbing)
Channel subfield CCCC = channel # or generic
L3 Explicit Writeback 17AH
0000_0001_0111_1010
000F 0001 RRRR TTLL (Cache Hierarchy Error) where
Request subfields RRRR = 0111B (Eviction)
Transaction Type subfields TT = 10B (Generic)
Level subfields LL = 10B
NOTES:
1. Note that for both of these errors the correction report filtering (F) bit (bit 12) of the MCA error must be ignored.
Table 15-16 lists values of relevant bit fields of IA32_MCi_STATUS for architecturally defined SRAO errors.
Table 15-16. IA32_MCi_STATUS Values for SRAO Errors
SRAO Error
Memory Scrubbing
L3 Explicit Writeback
Valid
1
1
OVER
0
0
UC
1
1
EN
x
1
x
1
MISCV
1
1
ADDRV
1
1
PCC
S
AR
MCACOD
0
x1
0
C0H-CFH
0
x1
0
17AH
Vol. 3B 15-23
MACHINE-CHECK ARCHITECTURE
NOTES:
1. When signaled as MCE, EN=1 and S=1. If error was signaled via CMC, then EN=x, and S=0.
For both the memory scrubbing and L3 explicit writeback errors, the ADDRV and MISCV flags in the
IA32_MCi_STATUS register are set to indicate that the offending physical address information is available from the
IA32_MCi_MISC and the IA32_MCi_ADDR registers. For the memory scrubbing and L3 explicit writeback errors,
the address mode in the IA32_MCi_MISC register should be set as physical address mode (010b) and the address
LSB information in the IA32_MCi_MISC register should indicate the lowest valid address bit in the address information provided from the IA32_MCi_ADDR register.
MCE signal is broadcast to all logical processors as outlined in Section 15.10.4.1. If LMCE is supported and enabled,
some errors (not limited to UCR errors) may be delivered to only a single logical processor. System software should
consult IA32_MCG_STATUS.LMCE_S to determine if the MCE signaled is only to this logical processor.
IA32_MCi_STATUS banks can be shared by logical processors within a core or within the same package. So several
logical processors may find an SRAO error in the shared IA32_MCi_STATUS bank but other processors do not find
it in any of the IA32_MCi_STATUS banks. Table 15-17 shows the RIPV and EIPV flag indication in the
IA32_MCG_STATUS register for the memory scrubbing and L3 explicit writeback errors on both the reporting and
non-reporting logical processors.
Table 15-17. IA32_MCG_STATUS Flag Indication for SRAO Errors
SRAO Type
Reporting Logical Processors
Non-reporting Logical Processors
RIPV
EIPV
RIPV
EIPV
Memory Scrubbing
1
0
1
0
L3 Explicit Writeback
1
0
1
0
15.9.3.2
Architecturally Defined SRAR Errors
The following two SRAR errors are architecturally defined.
•
•
UCR Errors detected on data load; and
UCR Errors detected on instruction fetch.
The MCA error code encodings for these two architecturally-defined UCR errors corresponds to sub-classes of
compound MCA error codes (see Table 15-9). Their values and compound encoding format are given in Table
15-18.
Table 15-18. MCA Compound Error Code Encoding for SRAR Errors
Type
MCACOD Value
Data Load
134H
MCA Error Code Encoding1
0000_0001_0011_0100
000F 0001 RRRR TTLL (Cache Hierarchy Error), where
Request subfield RRRR = 0011B (Data Load)
Transaction Type subfield TT= 01B (Data)
Level subfield LL = 00B (Level 0)
Instruction Fetch
150H
0000_0001_0101_0000
000F 0001 RRRR TTLL (Cache Hierarchy Error), where
Request subfield RRRR = 0101B (Instruction Fetch)
Transaction Type subfield TT= 00B (Instruction)
Level subfield LL = 00B (Level 0)
NOTES:
1. Note that for both of these errors the correction report filtering (F) bit (bit 12) of the MCA error must be ignored.
15-24 Vol. 3B
MACHINE-CHECK ARCHITECTURE
Table 15-19 lists values of relevant bit fields of IA32_MCi_STATUS for architecturally defined SRAR errors.
Table 15-19. IA32_MCi_STATUS Values for SRAR Errors
SRAR Error
Valid
OVER
UC
EN
MISCV
ADDRV
PCC
S
AR
MCACOD
Data Load
1
0
1
1
1
1
0
1
1
134H
Instruction Fetch
1
0
1
1
1
1
0
1
1
150H
For both the data load and instruction fetch errors, the ADDRV and MISCV flags in the IA32_MCi_STATUS register
are set to indicate that the offending physical address information is available from the IA32_MCi_MISC and the
IA32_MCi_ADDR registers. For the memory scrubbing and L3 explicit writeback errors, the address mode in the
IA32_MCi_MISC register should be set as physical address mode (010b) and the address LSB information in the
IA32_MCi_MISC register should indicate the lowest valid address bit in the address information provided from the
IA32_MCi_ADDR register.
MCE signal is broadcast to all logical processors on the system on which the UCR errors are supported, except when
the processor supports LMCE and LMCE is enabled by system software (see Section 15.3.1.5). The
IA32_MCG_STATUS MSR allows system software to distinguish the affected logical processor of an SRAR error
amongst logical processors that observed SRAR via MCi_STATUS bank.
Table 15-20 shows the RIPV and EIPV flag indication in the IA32_MCG_STATUS register for the data load and
instruction fetch errors on both the reporting and non-reporting logical processors. The recoverable SRAR error
reported by a processor may be continuable, where the system software can interpret the context of continuable
as follows: the error was isolated, contained. If software can rectify the error condition in the current instruction
stream, the execution context on that logical processor can be continued without loss of information.
Table 15-20. IA32_MCG_STATUS Flag Indication for SRAR Errors
SRAR Type
Affected Logical Processor
RIPV
EIPV
Non-Affected Logical Processors
Continuable
Recoverablecontinuable
1
1
Yes
Recoverable-notcontinuable
0
x
No
RIPV
EIPV
Continuable
1
1
0
Yes
NOTES:
1. see the definition of the context of “continuable” above and additional detail below.
SRAR Error And Affected Logical Processors
The affected logical processor is the one that has detected and raised an SRAR error at the point of the consumption in the execution flow. The affected logical processor should find the Data Load or the Instruction Fetch error
information in the IA32_MCi_STATUS register that is reporting the SRAR error.
Table 15-20 list the actionable scenarios that system software can respond to an SRAR error on an affected logical
processor according to RIPV and EIPV values:
•
Recoverable-Continuable SRAR Error (RIPV=1, EIPV=1):
For Recoverable-Continuable SRAR errors, the affected logical processor should find that both the
IA32_MCG_STATUS.RIPV and the IA32_MCG_STATUS.EIPV flags are set, indicating that system software may
be able to restart execution from the interrupted context if it is able to rectify the error condition. If system
software cannot rectify the error condition then it must treat the error as a recoverable error where restarting
execution with the interrupted context is not possible. Restarting without rectifying the error condition will
result in most cases with another SRAR error on the same instruction.
•
Recoverable-not-continuable SRAR Error (RIPV=0, EIPV=x):
For Recoverable-not-continuable errors, the affected logical processor should find that either
— IA32_MCG_STATUS.RIPV= 0, IA32_MCG_STATUS.EIPV=1, or
— IA32_MCG_STATUS.RIPV= 0, IA32_MCG_STATUS.EIPV=0.
Vol. 3B 15-25
MACHINE-CHECK ARCHITECTURE
In either case, this indicates that the error is detected at the instruction pointer saved on the stack for this
machine check exception and restarting execution with the interrupted context is not possible. System
software may take the following recovery actions for the affected logical processor:
•
The current executing thread cannot be continued. System software must terminate the interrupted
stream of execution and provide a new stream of execution on return from the machine check handler
for the affected logical processor.
SRAR Error And Non-Affected Logical Processors
The logical processors that observed but not affected by an SRAR error should find that the RIPV flag in the
IA32_MCG_STATUS register is set and the EIPV flag in the IA32_MCG_STATUS register is cleared, indicating that it
is safe to restart the execution at the instruction saved on the stack for the machine check exception on these
processors after the recovery action is successfully taken by system software.
15.9.4
Multiple MCA Errors
When multiple MCA errors are detected within a certain detection window, the processor may aggregate the
reporting of these errors together as a single event, i.e. a single machine exception condition. If this occurs,
system software may find multiple MCA errors logged in different MC banks on one logical processor or find multiple
MCA errors logged across different processors for a single machine check broadcast event. In order to handle
multiple UCR errors reported from a single machine check event and possibly recover from multiple errors, system
software may consider the following:
•
Whether it can recover from multiple errors is determined by the most severe error reported on the system. If
the most severe error is found to be an unrecoverable error (VAL=1, UC=1, PCC=1 and EN=1) after system
software examines the MC banks of all processors to which the MCA signal is broadcast, recovery from the
multiple errors is not possible and system software needs to reset the system.
•
When multiple recoverable errors are reported and no other fatal condition (e.g. overflowed condition for SRAR
error) is found for the reported recoverable errors, it is possible for system software to recover from the
multiple recoverable errors by taking necessary recovery action for each individual recoverable error. However,
system software can no longer expect one to one relationship with the error information recorded in the
IA32_MCi_STATUS register and the states of the RIPV and EIPV flags in the IA32_MCG_STATUS register as the
states of the RIPV and the EIPV flags in the IA32_MCG_STATUS register may indicate the information for the
most severe error recorded on the processor. System software is required to use the RIPV flag indication in the
IA32_MCG_STATUS register to make a final decision of recoverability of the errors and find the restart-ability
requirement after examining each IA32_MCi_STATUS register error information in the MC banks.
In certain cases where system software observes more than one SRAR error logged for a single logical
processor, it can no longer rely on affected threads as specified in Table 15-20 above. System software is
recommended to reset the system if this condition is observed.
15.9.5
Machine-Check Error Codes Interpretation
Chapter 16, “Interpreting Machine-Check Error Codes,” provides information on interpreting the MCA error code,
model-specific error code, and other information error code fields. For P6 family processors, information has been
included on decoding external bus errors. For Pentium 4 and Intel Xeon processors; information is included on
external bus, internal timer and cache hierarchy errors.
15.10
GUIDELINES FOR WRITING MACHINE-CHECK SOFTWARE
The machine-check architecture and error logging can be used in three different ways:
•
•
•
To detect machine errors during normal instruction execution, using the machine-check exception (#MC).
To periodically check and log machine errors.
To examine recoverable UCR errors, determine software recoverability and perform recovery actions via a
machine-check exception handler or a corrected machine-check interrupt handler.
15-26 Vol. 3B
MACHINE-CHECK ARCHITECTURE
To use the machine-check exception, the operating system or executive software must provide a machine-check
exception handler. This handler may need to be designed specifically for each family of processors.
A special program or utility is required to log machine errors.
Guidelines for writing a machine-check exception handler or a machine-error logging utility are given in the
following sections.
15.10.1 Machine-Check Exception Handler
The machine-check exception (#MC) corresponds to vector 18. To service machine-check exceptions, a trap gate
must be added to the IDT. The pointer in the trap gate must point to a machine-check exception handler. Two
approaches can be taken to designing the exception handler:
1. The handler can merely log all the machine status and error information, then call a debugger or shut down the
system.
2. The handler can analyze the reported error information and, in some cases, attempt to correct the error and
restart the processor.
For Pentium 4, Intel Xeon, Intel Atom, P6 family, and Pentium processors; virtually all machine-check conditions
cannot be corrected (they result in abort-type exceptions). The logging of status and error information is therefore
a baseline implementation requirement.
When IA32_MCG_CAP[24] is clear, consider the following when writing a machine-check exception handler:
•
To determine the nature of the error, the handler must read each of the error-reporting register banks. The
count field in the IA32_MCG_CAP register gives number of register banks. The first register of register bank 0
is at address 400H.
•
The VAL (valid) flag in each IA32_MCi_STATUS register indicates whether the error information in the register
is valid. If this flag is clear, the registers in that bank do not contain valid error information and do not need to
be checked.
•
To write a portable exception handler, only the MCA error code field in the IA32_MCi_STATUS register should be
checked. See Section 15.9, “Interpreting the MCA Error Codes,” for information that can be used to write an
algorithm to interpret this field.
•
Correctable errors are corrected automatically by the processor. The UC flag in each IA32_MCi_STATUS register indicates whether the processor automatically corrected an error.
•
The RIPV, PCC, and OVER flags in each IA32_MCi_STATUS register indicate whether recovery from the error is
possible. If PCC or OVER are set, recovery is not possible. If RIPV is not set, program execution can not be
restarted reliably. When recovery is not possible, the handler typically records the error information and signals
an abort to the operating system.
•
The RIPV flag in the IA32_MCG_STATUS register indicates whether the program can be restarted at the
instruction indicated by the instruction pointer (the address of the instruction pushed on the stack when the
exception was generated). If this flag is clear, the processor may still be able to be restarted (for debugging
purposes) but not without loss of program continuity.
•
For unrecoverable errors, the EIPV flag in the IA32_MCG_STATUS register indicates whether the instruction
indicated by the instruction pointer pushed on the stack (when the exception was generated) is related to the
error. If the flag is clear, the pushed instruction may not be related to the error.
•
The MCIP flag in the IA32_MCG_STATUS register indicates whether a machine-check exception was generated.
Before returning from the machine-check exception handler, software should clear this flag so that it can be
used reliably by an error logging utility. The MCIP flag also detects recursion. The machine-check architecture
does not support recursion. When the processor detects machine-check recursion, it enters the shutdown
state.
Example 15-2 gives typical steps carried out by a machine-check exception handler.
Vol. 3B 15-27
MACHINE-CHECK ARCHITECTURE
Example 15-2. Machine-Check Exception Handler Pseudocode
IF CPU supports MCE
THEN
IF CPU supports MCA
THEN
call errorlogging routine; (* returns restartability *)
FI;
ELSE (* Pentium(R) processor compatible *)
READ P5_MC_ADDR
READ P5_MC_TYPE;
report RESTARTABILITY to console;
FI;
IF error is not restartable
THEN
report RESTARTABILITY to console;
abort system;
FI;
CLEAR MCIP flag in IA32_MCG_STATUS;
15.10.2 Pentium Processor Machine-Check Exception Handling
Machine-check exception handler on P6 family, Intel Atom and later processor families, should follow the guidelines
described in Section 15.10.1 and Example 15-2 that check the processor’s support of MCA.
NOTE
On processors that support MCA (CPUID.1.EDX.MCA = 1) reading the P5_MC_TYPE and
P5_MC_ADDR registers may produce invalid data.
When machine-check exceptions are enabled for the Pentium processor (MCE flag is set in control register CR4),
the machine-check exception handler uses the RDMSR instruction to read the error type from the P5_MC_TYPE
register and the machine check address from the P5_MC_ADDR register. The handler then normally reports these
register values to the system console before aborting execution (see Example 15-2).
15.10.3 Logging Correctable Machine-Check Errors
The error handling routine for servicing the machine-check exceptions is responsible for logging uncorrected
errors.
If a machine-check error is correctable, the processor does not generate a machine-check exception for it. To
detect correctable machine-check errors, a utility program must be written that reads each of the machine-check
error-reporting register banks and logs the results in an accounting file or data structure. This utility can be implemented in either of the following ways.
•
•
A system daemon that polls the register banks on an infrequent basis, such as hourly or daily.
•
An interrupt service routine servicing CMCI can read the MC banks and log the error. Please refer to Section
15.10.4.2 for guidelines on logging correctable machine checks.
A user-initiated application that polls the register banks and records the exceptions. Here, the actual polling
service is provided by an operating-system driver or through the system call interface.
Example 15-3 gives pseudocode for an error logging utility.
15-28 Vol. 3B
MACHINE-CHECK ARCHITECTURE
Example 15-3. Machine-Check Error Logging Pseudocode
Assume that execution is restartable;
IF the processor supports MCA
THEN
FOR each bank of machine-check registers
DO
READ IA32_MCi_STATUS;
IF VAL flag in IA32_MCi_STATUS = 1
THEN
IF ADDRV flag in IA32_MCi_STATUS = 1
THEN READ IA32_MCi_ADDR;
FI;
IF MISCV flag in IA32_MCi_STATUS = 1
THEN READ IA32_MCi_MISC;
FI;
IF MCIP flag in IA32_MCG_STATUS = 1
(* Machine-check exception is in progress *)
AND PCC flag in IA32_MCi_STATUS = 1
OR RIPV flag in IA32_MCG_STATUS = 0
(* execution is not restartable *)
THEN
RESTARTABILITY = FALSE;
return RESTARTABILITY to calling procedure;
FI;
Save time-stamp counter and processor ID;
Set IA32_MCi_STATUS to all 0s;
Execute serializing instruction (i.e., CPUID);
FI;
OD;
FI;
If the processor supports the machine-check architecture, the utility reads through the banks of error-reporting
registers looking for valid register entries. It then saves the values of the IA32_MCi_STATUS, IA32_MCi_ADDR,
IA32_MCi_MISC and IA32_MCG_STATUS registers for each bank that is valid. The routine minimizes processing
time by recording the raw data into a system data structure or file, reducing the overhead associated with polling.
User utilities analyze the collected data in an off-line environment.
When the MCIP flag is set in the IA32_MCG_STATUS register, a machine-check exception is in progress and the
machine-check exception handler has called the exception logging routine.
Once the logging process has been completed the exception-handling routine must determine whether execution
can be restarted, which is usually possible when damage has not occurred (The PCC flag is clear, in the
IA32_MCi_STATUS register) and when the processor can guarantee that execution is restartable (the RIPV flag is
set in the IA32_MCG_STATUS register). If execution cannot be restarted, the system is not recoverable and the
exception-handling routine should signal the console appropriately before returning the error status to the Operating System kernel for subsequent shutdown.
The machine-check architecture allows buffering of exceptions from a given error-reporting bank although the
Pentium 4, Intel Xeon, Intel Atom, and P6 family processors do not implement this feature. The error logging
routine should provide compatibility with future processors by reading each hardware error-reporting bank's
IA32_MCi_STATUS register and then writing 0s to clear the OVER and VAL flags in this register. The error logging
utility should re-read the IA32_MCi_STATUS register for the bank ensuring that the valid bit is clear. The processor
will write the next error into the register bank and set the VAL flags.
Additional information that should be stored by the exception-logging routine includes the processor’s time-stamp
counter value, which provides a mechanism to indicate the frequency of exceptions. A multiprocessing operating
system stores the identity of the processor node incurring the exception using a unique identifier, such as the
processor’s APIC ID (see Section 10.8, “Handling Interrupts”).
The basic algorithm given in Example 15-3 can be modified to provide more robust recovery techniques. For
example, software has the flexibility to attempt recovery using information unavailable to the hardware. Specifically, the machine-check exception handler can, after logging carefully analyze the error-reporting registers when
the error-logging routine reports an error that does not allow execution to be restarted. These recovery techniques
Vol. 3B 15-29
MACHINE-CHECK ARCHITECTURE
can use external bus related model-specific information provided with the error report to localize the source of the
error within the system and determine the appropriate recovery strategy.
15.10.4 Machine-Check Software Handler Guidelines for Error Recovery
15.10.4.1 Machine-Check Exception Handler for Error Recovery
When writing a machine-check exception (MCE) handler to support software recovery from Uncorrected Recoverable (UCR) errors, consider the following:
•
When IA32_MCG_CAP [24] is zero, there are no recoverable errors supported and all machine-check are fatal
exceptions. The logging of status and error information is therefore a baseline implementation requirement.
•
When IA32_MCG_CAP [24] is 1, certain uncorrected errors called uncorrected recoverable (UCR) errors may be
software recoverable. The handler can analyze the reported error information, and in some cases attempt to
recover from the uncorrected error and continue execution.
•
For processors on which CPUID reports DisplayFamily_DisplayModel as 06H_0EH and onward, an MCA signal is
broadcast to all logical processors in the system (see CPUID instruction in Chapter 3, “Instruction Set
Reference, A-M” in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 2A). Due to
the potentially shared machine check MSR resources among the logical processors on the same package/core,
the MCE handler may be required to synchronize with the other processors that received a machine check error
and serialize access to the machine check registers when analyzing, logging and clearing the information in the
machine check registers.
— On processors that indicate ability for local machine-check exception (MCG_LMCE_P), hardware can choose
to report the error to only a single logical processor if system software has enabled LMCE by setting
IA32_MCG_EXT_CTL[LMCE_EN] = 1 as outlined in Section 15.3.1.5.
•
The VAL (valid) flag in each IA32_MCi_STATUS register indicates whether the error information in the register
is valid. If this flag is clear, the registers in that bank do not contain valid error information and should not be
checked.
•
The MCE handler is primarily responsible for processing uncorrected errors. The UC flag in each
IA32_MCi_Status register indicates whether the reported error was corrected (UC=0) or uncorrected (UC=1).
The MCE handler can optionally log and clear the corrected errors in the MC banks if it can implement software
algorithm to avoid the undesired race conditions with the CMCI or CMC polling handler.
•
For uncorrectable errors, the EIPV flag in the IA32_MCG_STATUS register indicates (when set) that the
instruction pointed to by the instruction pointer pushed onto the stack when the machine-check exception is
generated is directly associated with the error. When this flag is cleared, the instruction pointed to may not be
associated with the error.
•
The MCIP flag in the IA32_MCG_STATUS register indicates whether a machine-check exception was generated.
When a machine check exception is generated, it is expected that the MCIP flag in the IA32_MCG_STATUS
register is set to 1. If it is not set, this machine check was generated by either an INT 18 instruction or some
piece of hardware signaling an interrupt with vector 18.
When IA32_MCG_CAP [24] is 1, the following rules can apply when writing a machine check exception (MCE)
handler to support software recovery:
•
The PCC flag in each IA32_MCi_STATUS register indicates whether recovery from the error is possible for
uncorrected errors (UC=1). If the PCC flag is set for enabled uncorrected errors (UC=1 and EN=1), recovery is
not possible. When recovery is not possible, the MCE handler typically records the error information and signals
the operating system to reset the system.
•
The RIPV flag in the IA32_MCG_STATUS register indicates whether restarting the program execution from the
instruction pointer saved on the stack for the machine check exception is possible. When the RIPV is set,
program execution can be restarted reliably when recovery is possible. If the RIPV flag is not set, program
execution cannot be restarted reliably. In this case the recovery algorithm may involve terminating the current
program execution and resuming an alternate thread of execution upon return from the machine check handler
when recovery is possible. When recovery is not possible, the MCE handler signals the operating system to
reset the system.
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MACHINE-CHECK ARCHITECTURE
•
When the EN flag is zero but the VAL and UC flags are one in the IA32_MCi_STATUS register, the reported
uncorrected error in this bank is not enabled. As uncorrected errors with the EN flag = 0 are not the source of
machine check exceptions, the MCE handler should log and clear non-enabled errors when the S bit is set and
should continue searching for enabled errors from the other IA32_MCi_STATUS registers. Note that when
IA32_MCG_CAP [24] is 0, any uncorrected error condition (VAL =1 and UC=1) including the one with the EN
flag cleared are fatal and the handler must signal the operating system to reset the system. For the errors that
do not generate machine check exceptions, the EN flag has no meaning.
•
When the VAL flag is one, the UC flag is one, the EN flag is one and the PCC flag is zero in the
IA32_MCi_STATUS register, the error in this bank is an uncorrected recoverable (UCR) error. The MCE handler
needs to examine the S flag and the AR flag to find the type of the UCR error for software recovery and
determine if software error recovery is possible.
•
When both the S and the AR flags are clear in the IA32_MCi_STATUS register for the UCR error (VAL=1, UC=1,
EN=x and PCC=0), the error in this bank is an uncorrected no-action required error (UCNA). UCNA errors are
uncorrected but do not require any OS recovery action to continue execution. These errors indicate that some
data in the system is corrupt, but that data has not been consumed and may not be consumed. If that data is
consumed a non-UNCA machine check exception will be generated. UCNA errors are signaled in the same way
as corrected machine check errors and the CMCI and CMC polling handler is primarily responsible for handling
UCNA errors. Like corrected errors, the MCA handler can optionally log and clear UCNA errors as long as it can
avoid the undesired race condition with the CMCI or CMC polling handler. As UCNA errors are not the source of
machine check exceptions, the MCA handler should continue searching for uncorrected or software recoverable
errors in all other MC banks.
•
When the S flag in the IA32_MCi_STATUS register is set for the UCR error ((VAL=1, UC=1, EN=1 and PCC=0),
the error in this bank is software recoverable and it was signaled through a machine-check exception. The AR
flag in the IA32_MCi_STATUS register further clarifies the type of the software recoverable errors.
•
When the AR flag in the IA32_MCi_STATUS register is clear for the software recoverable error (VAL=1, UC=1,
EN=1, PCC=0 and S=1), the error in this bank is a software recoverable action optional (SRAO) error. The MCE
handler and the operating system can analyze the IA32_MCi_STATUS [15:0] to implement MCA error code
specific optional recovery action, but this recovery action is optional. System software can resume the program
execution from the instruction pointer saved on the stack for the machine check exception when the RIPV flag
in the IA32_MCG_STATUS register is set.
•
Even if the OVER flag in the IA32_MCi_STATUS register is set for the SRAO error (VAL=1, UC=1, EN=1, PCC=0,
S=1 and AR=0), the MCE handler can take recovery action for the SRAO error logged in the IA32_MCi_STATUS
register. Since the recovery action for SRAO errors is optional, restarting the program execution from the
instruction pointer saved on the stack for the machine check exception is still possible for the overflowed SRAO
error if the RIPV flag in the IA32_MCG_STATUS is set.
•
When the AR flag in the IA32_MCi_STATUS register is set for the software recoverable error (VAL=1, UC=1,
EN=1, PCC=0 and S=1), the error in this bank is a software recoverable action required (SRAR) error. The MCE
handler and the operating system must take recovery action in order to continue execution after the machinecheck exception. The MCA handler and the operating system need to analyze the IA32_MCi_STATUS [15:0] to
determine the MCA error code specific recovery action. If no recovery action can be performed, the operating
system must reset the system.
•
When the OVER flag in the IA32_MCi_STATUS register is set for the SRAR error (VAL=1, UC=1, EN=1, PCC=0,
S=1 and AR=1), the MCE handler cannot take recovery action as the information of the SRAR error in the
IA32_MCi_STATUS register was potentially lost due to the overflow condition. Since the recovery action for
SRAR errors must be taken, the MCE handler must signal the operating system to reset the system.
•
When the MCE handler cannot find any uncorrected (VAL=1, UC=1 and EN=1) or any software recoverable
errors (VAL=1, UC=1, EN=1, PCC=0 and S=1) in any of the IA32_MCi banks of the processors, this is an
unexpected condition for the MCE handler and the handler should signal the operating system to reset the
system.
•
Before returning from the machine-check exception handler, software must clear the MCIP flag in the
IA32_MCG_STATUS register. The MCIP flag is used to detect recursion. The machine-check architecture does
not support recursion. When the processor receives a machine check when MCIP is set, it automatically enters
the shutdown state.
Example 15-4 gives pseudocode for an MC exception handler that supports recovery of UCR.
Vol. 3B 15-31
MACHINE-CHECK ARCHITECTURE
Example 15-4. Machine-Check Error Handler Pseudocode Supporting UCR
MACHINE CHECK HANDLER: (* Called from INT 18 handler *)
NOERROR = TRUE;
ProcessorCount = 0;
IF CPU supports MCA
THEN
RESTARTABILITY = TRUE;
IF (Processor Family = 6 AND DisplayModel ≥ 0EH) OR (Processor Family > 6)
THEN
IF ( MCG_LMCE = 1)
MCA_BROADCAST = FALSE;
ELSE
MCA_BROADCAST = TRUE;
FI;
Acquire SpinLock;
ProcessorCount++; (* Allowing one logical processor at a time to examine machine check registers *)
CALL MCA ERROR PROCESSING; (* returns RESTARTABILITY and NOERROR *)
ELSE
MCA_BROADCAST = FALSE;
(* Implement a rendezvous mechanism with the other processors if necessary *)
CALL MCA ERROR PROCESSING;
FI;
ELSE (* Pentium(R) processor compatible *)
READ P5_MC_ADDR
READ P5_MC_TYPE;
RESTARTABILITY = FALSE;
FI;
IF NOERROR = TRUE
THEN
IF NOT (MCG_RIPV = 1 AND MCG_EIPV = 0)
THEN
RESTARTABILITY = FALSE;
FI
FI;
IF RESTARTABILITY = FALSE
THEN
Report RESTARTABILITY to console;
Reset system;
FI;
IF MCA_BROADCAST = TRUE
THEN
IF ProcessorCount = MAX_PROCESSORS
AND NOERROR = TRUE
THEN
Report RESTARTABILITY to console;
Reset system;
FI;
Release SpinLock;
Wait till ProcessorCount = MAX_PROCESSRS on system;
(* implement a timeout and abort function if necessary *)
FI;
CLEAR IA32_MCG_STATUS;
RESUME Execution;
(* End of MACHINE CHECK HANDLER*)
MCA ERROR PROCESSING: (* MCA Error Processing Routine called from MCA Handler *)
IF MCIP flag in IA32_MCG_STATUS = 0
THEN (* MCIP=0 upon MCA is unexpected *)
RESTARTABILITY = FALSE;
FI;
15-32 Vol. 3B
MACHINE-CHECK ARCHITECTURE
FOR each bank of machine-check registers
DO
CLEAR_MC_BANK = FALSE;
READ IA32_MCi_STATUS;
IF VAL Flag in IA32_MCi_STATUS = 1
THEN
IF UC Flag in IA32_MCi_STATUS = 1
THEN
IF Bit 24 in IA32_MCG_CAP = 0
THEN (* the processor does not support software error recovery *)
RESTARTABILITY = FALSE;
NOERROR = FALSE;
GOTO LOG MCA REGISTER;
FI;
(* the processor supports software error recovery *)
IF EN Flag in IA32_MCi_STATUS = 0 AND OVER Flag in IA32_MCi_STATUS=0
THEN (* It is a spurious MCA Log. Log and clear the register *)
CLEAR_MC_BANK = TRUE;
GOTO LOG MCA REGISTER;
FI;
IF PCC = 1 and EN = 1 in IA32_MCi_STATUS
THEN (* processor context might have been corrupted *)
RESTARTABILITY = FALSE;
ELSE (* It is a uncorrected recoverable (UCR) error *)
IF S Flag in IA32_MCi_STATUS = 0
THEN
IF AR Flag in IA32_MCi_STATUS = 0
THEN (* It is a uncorrected no action required (UCNA) error *)
GOTO CONTINUE; (* let CMCI and CMC polling handler to process *)
ELSE
RESTARTABILITY = FALSE; (* S=0, AR=1 is illegal *)
FI
FI;
IF RESTARTABILITY = FALSE
THEN (* no need to take recovery action if RESTARTABILITY is already false *)
NOERROR = FALSE;
GOTO LOG MCA REGISTER;
FI;
(* S in IA32_MCi_STATUS = 1 *)
IF AR Flag in IA32_MCi_STATUS = 1
THEN (* It is a software recoverable and action required (SRAR) error *)
IF OVER Flag in IA32_MCi_STATUS = 1
THEN
RESTARTABILITY = FALSE;
NOERROR = FALSE;
GOTO LOG MCA REGISTER;
FI
IF MCACOD Value in IA32_MCi_STATUS is recognized
AND Current Processor is an Affected Processor
THEN
Implement MCACOD specific recovery action;
CLEAR_MC_BANK = TRUE;
ELSE
RESTARTABILITY = FALSE;
FI;
ELSE (* It is a software recoverable and action optional (SRAO) error *)
IF OVER Flag in IA32_MCi_STATUS = 0 AND
MCACOD in IA32_MCi_STATUS is recognized
THEN
Implement MCACOD specific recovery action;
FI;
CLEAR_MC_BANK = TRUE;
FI; AR
FI; PCC
NOERROR = FALSE;
Vol. 3B 15-33
MACHINE-CHECK ARCHITECTURE
GOTO LOG MCA REGISTER;
ELSE (* It is a corrected error; continue to the next IA32_MCi_STATUS *)
GOTO CONTINUE;
FI; UC
FI; VAL
LOG MCA REGISTER:
SAVE IA32_MCi_STATUS;
If MISCV in IA32_MCi_STATUS
THEN
SAVE IA32_MCi_MISC;
FI;
IF ADDRV in IA32_MCi_STATUS
THEN
SAVE IA32_MCi_ADDR;
FI;
IF CLEAR_MC_BANK = TRUE
THEN
SET all 0 to IA32_MCi_STATUS;
If MISCV in IA32_MCi_STATUS
THEN
SET all 0 to IA32_MCi_MISC;
FI;
IF ADDRV in IA32_MCi_STATUS
THEN
SET all 0 to IA32_MCi_ADDR;
FI;
FI;
CONTINUE:
OD;
( *END FOR *)
RETURN;
(* End of MCA ERROR PROCESSING*)
15.10.4.2 Corrected Machine-Check Handler for Error Recovery
When writing a corrected machine check handler, which is invoked as a result of CMCI or called from an OS CMC
Polling dispatcher, consider the following:
•
The VAL (valid) flag in each IA32_MCi_STATUS register indicates whether the error information in the register
is valid. If this flag is clear, the registers in that bank does not contain valid error information and does not need
to be checked.
•
The CMCI or CMC polling handler is responsible for logging and clearing corrected errors. The UC flag in each
IA32_MCi_Status register indicates whether the reported error was corrected (UC=0) or not (UC=1).
•
When IA32_MCG_CAP [24] is one, the CMC handler is also responsible for logging and clearing uncorrected noaction required (UCNA) errors. When the UC flag is one but the PCC, S, and AR flags are zero in the
IA32_MCi_STATUS register, the reported error in this bank is an uncorrected no-action required (UCNA) error.
In cases when SRAO error are signaled as UCNA error via CMCI, software can perform recovery for those errors
identified in Table 15-15.
•
In addition to corrected errors and UCNA errors, the CMC handler optionally logs uncorrected (UC=1 and
PCC=1), software recoverable machine check errors (UC=1, PCC=0 and S=1), but should avoid clearing those
errors from the MC banks. Clearing these errors may result in accidentally removing these errors before these
errors are actually handled and processed by the MCE handler for attempted software error recovery.
Example 15-5 gives pseudocode for a CMCI handler with UCR support.
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MACHINE-CHECK ARCHITECTURE
Example 15-5. Corrected Error Handler Pseudocode with UCR Support
Corrected Error HANDLER: (* Called from CMCI handler or OS CMC Polling Dispatcher*)
IF CPU supports MCA
THEN
FOR each bank of machine-check registers
DO
READ IA32_MCi_STATUS;
IF VAL flag in IA32_MCi_STATUS = 1
THEN
IF UC Flag in IA32_MCi_STATUS = 0 (* It is a corrected error *)
THEN
GOTO LOG CMC ERROR;
ELSE
IF Bit 24 in IA32_MCG_CAP = 0
THEN
GOTO CONTINUE;
FI;
IF S Flag in IA32_MCi_STATUS = 0 AND AR Flag in IA32_MCi_STATUS = 0
THEN (* It is a uncorrected no action required error *)
GOTO LOG CMC ERROR
FI
IF EN Flag in IA32_MCi_STATUS = 0
THEN (* It is a spurious MCA error *)
GOTO LOG CMC ERROR
FI;
FI;
FI;
GOTO CONTINUE;
LOG CMC ERROR:
SAVE IA32_MCi_STATUS;
If MISCV Flag in IA32_MCi_STATUS
THEN
SAVE IA32_MCi_MISC;
SET all 0 to IA32_MCi_MISC;
FI;
IF ADDRV Flag in IA32_MCi_STATUS
THEN
SAVE IA32_MCi_ADDR;
SET all 0 to IA32_MCi_ADDR
FI;
SET all 0 to IA32_MCi_STATUS;
CONTINUE:
OD;
( *END FOR *)
FI;
Vol. 3B 15-35
MACHINE-CHECK ARCHITECTURE
15-36 Vol. 3B
CHAPTER 16
INTERPRETING MACHINE-CHECK
ERROR CODES
Encoding of the model-specific and other information fields is different across processor families. The differences
are documented in the following sections.
16.1
INCREMENTAL DECODING INFORMATION: PROCESSOR FAMILY 06H
MACHINE ERROR CODES FOR MACHINE CHECK
Section 16.1 provides information for interpreting additional model-specific fields for external bus errors relating to
processor family 06H. The references to processor family 06H refers to only IA-32 processors with CPUID signatures listed in Table 16-1.
Table 16-1. CPUID DisplayFamily_DisplayModel Signatures for Processor Family 06H
DisplayFamily_DisplayModel
Processor Families/Processor Number Series
06_0EH
Intel Core Duo, Intel Core Solo processors
06_0DH
Intel Pentium M processor
06_09H
Intel Pentium M processor
06_7H, 06_08H, 06_0AH, 06_0BH
Intel Pentium III Xeon Processor, Intel Pentium III Processor
06_03H, 06_05H
Intel Pentium II Xeon Processor, Intel Pentium II Processor
06_01H
Intel Pentium Pro Processor
These errors are reported in the IA32_MCi_STATUS MSRs. They are reported architecturally as compound errors
with a general form of 0000 1PPT RRRR IILL in the MCA error code field. See Chapter 15 for information on the
interpretation of compound error codes. Incremental decoding information is listed in Table 16-2.
Table 16-2. Incremental Decoding Information: Processor Family 06H Machine Error Codes For Machine Check
Type
Bit No.
Bit Function
Bit Description
MCA error
codes1
0-15
Model specific
errors
16-18
Reserved
Reserved
Model specific
errors
19-24
Bus queue request
type
000000 for BQ_DCU_READ_TYPE error
000010 for BQ_IFU_DEMAND_TYPE error
000011 for BQ_IFU_DEMAND_NC_TYPE error
000100 for BQ_DCU_RFO_TYPE error
000101 for BQ_DCU_RFO_LOCK_TYPE error
000110 for BQ_DCU_ITOM_TYPE error
001000 for BQ_DCU_WB_TYPE error
001010 for BQ_DCU_WCEVICT_TYPE error
001011 for BQ_DCU_WCLINE_TYPE error
001100 for BQ_DCU_BTM_TYPE error
Vol. 3B 16-1
INTERPRETING MACHINE-CHECK ERROR CODES
Table 16-2. Incremental Decoding Information: Processor Family 06H Machine Error Codes For Machine Check
Type
Bit No.
Bit Function
Bit Description
001101 for BQ_DCU_INTACK_TYPE error
001110 for BQ_DCU_INVALL2_TYPE error
001111 for BQ_DCU_FLUSHL2_TYPE error
010000 for BQ_DCU_PART_RD_TYPE error
010010 for BQ_DCU_PART_WR_TYPE error
010100 for BQ_DCU_SPEC_CYC_TYPE error
011000 for BQ_DCU_IO_RD_TYPE error
011001 for BQ_DCU_IO_WR_TYPE error
011100 for BQ_DCU_LOCK_RD_TYPE error
011110 for BQ_DCU_SPLOCK_RD_TYPE error
011101 for BQ_DCU_LOCK_WR_TYPE error
Model specific
errors
27-25
Bus queue error type
000 for BQ_ERR_HARD_TYPE error
001 for BQ_ERR_DOUBLE_TYPE error
010 for BQ_ERR_AERR2_TYPE error
100 for BQ_ERR_SINGLE_TYPE error
101 for BQ_ERR_AERR1_TYPE error
Model specific
errors
Other
information
28
FRC error
1 if FRC error active
29
BERR
1 if BERR is driven
30
Internal BINIT
1 if BINIT driven for this processor
31
Reserved
Reserved
32-34
Reserved
Reserved
35
External BINIT
1 if BINIT is received from external bus.
36
Response parity error This bit is asserted in IA32_MCi_STATUS if this component has received a parity
error on the RS[2:0]# pins for a response transaction. The RS signals are checked
by the RSP# external pin.
37
Bus BINIT
This bit is asserted in IA32_MCi_STATUS if this component has received a hard
error response on a split transaction one access that has needed to be split across
the 64-bit external bus interface into two accesses).
38
Timeout BINIT
This bit is asserted in IA32_MCi_STATUS if this component has experienced a ROB
time-out, which indicates that no micro-instruction has been retired for a
predetermined period of time.
A ROB time-out occurs when the 15-bit ROB time-out counter carries a 1 out of its
high order bit. 2 The timer is cleared when a micro-instruction retires, an exception
is detected by the core processor, RESET is asserted, or when a ROB BINIT occurs.
The ROB time-out counter is prescaled by the 8-bit PIC timer which is a divide by
128 of the bus clock the bus clock is 1:2, 1:3, 1:4 of the core clock). When a carry
out of the 8-bit PIC timer occurs, the ROB counter counts up by one. While this bit
is asserted, it cannot be overwritten by another error.
16-2 Vol. 3B
39-41
Reserved
Reserved
42
Hard error
This bit is asserted in IA32_MCi_STATUS if this component has initiated a bus
transactions which has received a hard error response. While this bit is asserted, it
cannot be overwritten.
INTERPRETING MACHINE-CHECK ERROR CODES
Table 16-2. Incremental Decoding Information: Processor Family 06H Machine Error Codes For Machine Check
Type
Bit No.
Bit Function
Bit Description
43
IERR
This bit is asserted in IA32_MCi_STATUS if this component has experienced a
failure that causes the IERR pin to be asserted. While this bit is asserted, it cannot
be overwritten.
44
AERR
This bit is asserted in IA32_MCi_STATUS if this component has initiated 2 failing
bus transactions which have failed due to Address Parity Errors AERR asserted).
While this bit is asserted, it cannot be overwritten.
45
UECC
The Uncorrectable ECC error bit is asserted in IA32_MCi_STATUS for uncorrected
ECC errors. While this bit is asserted, the ECC syndrome field will not be
overwritten.
46
CECC
The correctable ECC error bit is asserted in IA32_MCi_STATUS for corrected ECC
errors.
47-54
ECC syndrome
The ECC syndrome field in IA32_MCi_STATUS contains the 8-bit ECC syndrome only
if the error was a correctable/uncorrectable ECC error and there wasn't a previous
valid ECC error syndrome logged in IA32_MCi_STATUS.
A previous valid ECC error in IA32_MCi_STATUS is indicated by
IA32_MCi_STATUS.bit45 uncorrectable error occurred) being asserted. After
processing an ECC error, machine-check handling software should clear
IA32_MCi_STATUS.bit45 so that future ECC error syndromes can be logged.
55-56
Status register
validity
indicators1
Reserved
Reserved.
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
2. For processors with a CPUID signature of 06_0EH, a ROB time-out occurs when the 23-bit ROB time-out counter carries a 1 out of its
high order bit.
16.2
INCREMENTAL DECODING INFORMATION: INTEL CORE 2 PROCESSOR
FAMILY MACHINE ERROR CODES FOR MACHINE CHECK
Table 16-4 provides information for interpreting additional model-specific fields for external bus errors relating to
processor based on Intel Core microarchitecture, which implements the P4 bus specification. Table 16-3 lists the
CPUID signatures for Intel 64 processors that are covered by Table 16-4. These errors are reported in the
IA32_MCi_STATUS MSRs. They are reported architecturally as compound errors with a general form of
0000 1PPT RRRR IILL in the MCA error code field. See Chapter 15 for information on the interpretation of
compound error codes.
Table 16-3. CPUID DisplayFamily_DisplayModel Signatures for Processors Based on Intel Core Microarchitecture
DisplayFamily_DisplayModel Processor Families/Processor Number Series
06_1DH
Intel Xeon Processor 7400 series.
06_17H
Intel Xeon Processor 5200, 5400 series, Intel Core 2 Quad processor Q9650.
06_0FH
Intel Xeon Processor 3000, 3200, 5100, 5300, 7300 series, Intel Core 2 Quad, Intel Core 2 Extreme,
Intel Core 2 Duo processors, Intel Pentium dual-core processors.
Vol. 3B 16-3
INTERPRETING MACHINE-CHECK ERROR CODES
Table 16-4. Incremental Bus Error Codes of Machine Check for Processors
Based on Intel Core Microarchitecture
Type
Bit No.
Bit Function
Bit Description
MCA error
codes1
0-15
Model specific
errors
16-18
Reserved
Reserved
Model specific
errors
19-24
Bus queue request
type
‘000001 for BQ_PREF_READ_TYPE error
000000 for BQ_DCU_READ_TYPE error
000010 for BQ_IFU_DEMAND_TYPE error
000011 for BQ_IFU_DEMAND_NC_TYPE error
000100 for BQ_DCU_RFO_TYPE error
000101 for BQ_DCU_RFO_LOCK_TYPE error
000110 for BQ_DCU_ITOM_TYPE error
001000 for BQ_DCU_WB_TYPE error
001010 for BQ_DCU_WCEVICT_TYPE error
001011 for BQ_DCU_WCLINE_TYPE error
001100 for BQ_DCU_BTM_TYPE error
001101 for BQ_DCU_INTACK_TYPE error
001110 for BQ_DCU_INVALL2_TYPE error
001111 for BQ_DCU_FLUSHL2_TYPE error
010000 for BQ_DCU_PART_RD_TYPE error
010010 for BQ_DCU_PART_WR_TYPE error
010100 for BQ_DCU_SPEC_CYC_TYPE error
011000 for BQ_DCU_IO_RD_TYPE error
011001 for BQ_DCU_IO_WR_TYPE error
011100 for BQ_DCU_LOCK_RD_TYPE error
011110 for BQ_DCU_SPLOCK_RD_TYPE error
011101 for BQ_DCU_LOCK_WR_TYPE error
100100 for BQ_L2_WI_RFO_TYPE error
100110 for BQ_L2_WI_ITOM_TYPE error
Model specific
errors
27-25
Bus queue error type
‘001 for Address Parity Error
Model specific
errors
28
MCE Driven
1 if MCE is driven
29
MCE Observed
1 if MCE is observed
30
Internal BINIT
1 if BINIT driven for this processor
31
BINIT Observed
1 if BINIT is observed for this processor
32-33
Reserved
Reserved
34
PIC and FSB data
parity
Data Parity detected on either PIC or FSB access
35
Reserved
Reserved
‘010 for Response Hard Error
‘011 for Response Parity Error
Other
information
16-4 Vol. 3B
INTERPRETING MACHINE-CHECK ERROR CODES
Table 16-4. Incremental Bus Error Codes of Machine Check for Processors
Based on Intel Core Microarchitecture (Contd.)
Type
Bit No.
Bit Function
Bit Description
36
Response parity error This bit is asserted in IA32_MCi_STATUS if this component has received a parity
error on the RS[2:0]# pins for a response transaction. The RS signals are checked
by the RSP# external pin.
37
FSB address parity
Address parity error detected:
1 = Address parity error detected
0 = No address parity error
38
Timeout BINIT
This bit is asserted in IA32_MCi_STATUS if this component has experienced a ROB
time-out, which indicates that no micro-instruction has been retired for a
predetermined period of time.
A ROB time-out occurs when the 23-bit ROB time-out counter carries a 1 out of its
high order bit. The timer is cleared when a micro-instruction retires, an exception is
detected by the core processor, RESET is asserted, or when a ROB BINIT occurs.
The ROB time-out counter is prescaled by the 8-bit PIC timer which is a divide by
128 of the bus clock the bus clock is 1:2, 1:3, 1:4 of the core clock). When a carry
out of the 8-bit PIC timer occurs, the ROB counter counts up by one. While this bit
is asserted, it cannot be overwritten by another error.
Status register
validity
indicators1
39-41
Reserved
Reserved
42
Hard error
This bit is asserted in IA32_MCi_STATUS if this component has initiated a bus
transactions which has received a hard error response. While this bit is asserted, it
cannot be overwritten.
43
IERR
This bit is asserted in IA32_MCi_STATUS if this component has experienced a
failure that causes the IERR pin to be asserted. While this bit is asserted, it cannot
be overwritten.
44
Reserved
Reserved
45
Reserved
Reserved
46
Reserved
Reserved
47-54
Reserved
Reserved
55-56
Reserved
Reserved.
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
16.2.1
Model-Specific Machine Check Error Codes for Intel Xeon Processor 7400 Series
Intel Xeon processor 7400 series has machine check register banks that generally follows the description of
Chapter 15 and Section 16.2. Additional error codes specific to Intel Xeon processor 7400 series is describe in this
section.
MC4_STATUS[63:0] is the main error logging for the processor’s L3 and front side bus errors for Intel Xeon
processor 7400 series. It supports the L3 Errors, Bus and Interconnect Errors Compound Error Codes in the MCA
Error Code Field.
Vol. 3B 16-5
INTERPRETING MACHINE-CHECK ERROR CODES
16.2.1.1
Processor Machine Check Status Register
Incremental MCA Error Code Definition
Intel Xeon processor 7400 series use compound MCA Error Codes for logging its Bus internal machine check
errors, L3 Errors, and Bus/Interconnect Errors. It defines incremental Machine Check error types
(IA32_MC6_STATUS[15:0]) beyond those defined in Chapter 15. Table 16-5 lists these incremental MCA error
code types that apply to IA32_MC6_STATUS. Error code details are specified in MC6_STATUS [31:16] (see
Section 16.2.2), the “Model Specific Error Code” field. The information in the “Other_Info” field
(MC4_STATUS[56:32]) is common to the three processor error types and contains a correctable event count and
specifies the MC6_MISC register format.
Table 16-5. Incremental MCA Error Code Types for Intel Xeon Processor 7400
Processor MCA_Error_Code (MC6_STATUS[15:0])
Type
Error Code
Binary Encoding
Meaning
C
Internal Error
0000 0100 0000 0000 Internal Error Type Code
B
Bus and
Interconnect
0000 100x 0000 1111
Not used but this encoding is reserved for compatibility with other MCA
implementations
Error
0000 101x 0000 1111
Not used but this encoding is reserved for compatibility with other MCA
implementations
0000 110x 0000 1111
Not used but this encoding is reserved for compatibility with other MCA
implementations
0000 1110 0000 1111 Bus and Interconnection Error Type Code
0000 1111 0000 1111 Not used but this encoding is reserved for compatibility with other MCA
implementations
The Bold faced binary encodings are the only encodings used by the processor for MC4_STATUS[15:0].
16.2.2
Intel Xeon Processor 7400 Model Specific Error Code Field
16.2.2.1
Processor Model Specific Error Code Field
Type B: Bus and Interconnect Error
Note:
The Model Specific Error Code field in MC6_STATUS (bits 31:16).
Table 16-6. Type B Bus and Interconnect Error Codes
Bit Num
Sub-Field Name
Description
16
FSB Request Parity
Parity error detected during FSB request phase
19:17
Reserved
20
FSB Hard Fail Response
“Hard Failure“ response received for a local transaction
21
FSB Response Parity
Parity error on FSB response field detected
22
FSB Data Parity
FSB data parity error on inbound data detected
31:23
---
Reserved
16-6 Vol. 3B
INTERPRETING MACHINE-CHECK ERROR CODES
16.2.2.2
Processor Model Specific Error Code Field
Type C: Cache Bus Controller Error
Table 16-7. Type C Cache Bus Controller Error Codes
MC4_STATUS[31:16] (MSCE) Value
Error Description
0000_0000_0000_0001 0001H
Inclusion Error from Core 0
0000_0000_0000_0010 0002H
Inclusion Error from Core 1
0000_0000_0000_0011 0003H
Write Exclusive Error from Core 0
0000_0000_0000_0100 0004H
Write Exclusive Error from Core 1
0000_0000_0000_0101 0005H
Inclusion Error from FSB
0000_0000_0000_0110 0006H
SNP Stall Error from FSB
0000_0000_0000_0111 0007H
Write Stall Error from FSB
0000_0000_0000_1000 0008H
FSB Arb Timeout Error
0000_0000_0000_1010 000AH
Inclusion Error from Core 2
0000_0000_0000_1011 000BH
Write Exclusive Error from Core 2
0000_0010_0000_0000 0200H
Internal Timeout error
0000_0011_0000_0000 0300H
Internal Timeout Error
0000_0100_0000_0000 0400H
Intel® Cache Safe Technology Queue Full Error or Disabled-ways-in-a-set overflow
0000_0101_0000_0000 0500H
Quiet cycle Timeout Error (correctable)
1100_0000_0000_0010 C002H
Correctable ECC event on outgoing Core 0 data
1100_0000_0000_0100 C004H
Correctable ECC event on outgoing Core 1 data
1100_0000_0000_1000 C008H
Correctable ECC event on outgoing Core 2 data
1110_0000_0000_0010 E002H
Uncorrectable ECC error on outgoing Core 0 data
1110_0000_0000_0100 E004H
Uncorrectable ECC error on outgoing Core 1 data
1110_0000_0000_1000 E008H
Uncorrectable ECC error on outgoing Core 2 data
— all other encodings —
Reserved
16.3
INCREMENTAL DECODING INFORMATION: PROCESSOR FAMILY WITH
CPUID DISPLAYFAMILY_DISPLAYMODEL SIGNATURE 06_1AH, MACHINE
ERROR CODES FOR MACHINE CHECK
Table 16-8 through Table 16-12 provide information for interpreting additional model-specific fields for memory
controller errors relating to the processor family with CPUID DisplayFamily_DisplaySignature 06_1AH, which
supports Intel QuickPath Interconnect links. Incremental MC error codes related to the Intel QPI links are reported
in the register banks IA32_MC0 and IA32_MC1, incremental error codes for internal machine check is reported in
the register bank IA32_MC7, and incremental error codes for the memory controller unit is reported in the register
banks IA32_MC8.
Vol. 3B 16-7
INTERPRETING MACHINE-CHECK ERROR CODES
16.3.1
Intel QPI Machine Check Errors
Table 16-8. Intel QPI Machine Check Error Codes for IA32_MC0_STATUS and IA32_MC1_STATUS
Type
1
MCA error codes
Bit No.
Bit Function
Bit Description
0-15
MCACOD
Bus error format: 1PPTRRRRIILL
16
Header Parity
if 1, QPI Header had bad parity
17
Data Parity
If 1, QPI Data packet had bad parity
18
Retries Exceeded
If 1, number of QPI retries was exceeded
19
Received Poison
if 1, Received a data packet that was marked as poisoned by the sender
21-20
Reserved
Reserved
22
Unsupported Message
If 1, QPI received a message encoding it does not support
23
Unsupported Credit
If 1, QPI credit type is not supported.
24
Receive Flit Overrun
If 1, Sender sent too many QPI flits to the receiver.
25
Received Failed
Response
If 1, Indicates that sender sent a failed response to receiver.
26
Receiver Clock Jitter
If 1, clock jitter detected in the internal QPI clocking
56-27
Reserved
Reserved
Model specific errors
Status register
validity indicators1
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
Table 16-9. Intel QPI Machine Check Error Codes for IA32_MC0_MISC and IA32_MC1_MISC
Type
Model specific
Bit No.
Bit Function
Bit Description
7-0
QPI Opcode
Message class and opcode from the packet with the error
13-8
RTId
QPI Request Transaction ID
15-14
Reserved
Reserved
18-16
RHNID
QPI Requestor/Home Node ID
23-19
Reserved
Reserved
24
IIB
QPI Interleave/Head Indication Bit
errors1
NOTES:
1. Which of these fields are valid depends on the error type.
16.3.2
Internal Machine Check Errors
Table 16-10. Machine Check Error Codes for IA32_MC7_STATUS
Type
Bit No.
Bit Function
MCA error codes1
0-15
MCACOD
Model specific errors
16-8 Vol. 3B
Bit Description
INTERPRETING MACHINE-CHECK ERROR CODES
Type
Bit No.
Bit Function
Bit Description
23-16
Reserved
Reserved
31-24
Reserved except for
the following
00h - No Error
03h - Reset firmware did not complete
08h - Received an invalid CMPD
0Ah - Invalid Power Management Request
0Dh - Invalid S-state transition
11h - VID controller does not match POC controller selected
1Ah - MSID from POC does not match CPU MSID
56-32
Status register validity
indicators1
Reserved
Reserved
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
16.3.3
Memory Controller Errors
Table 16-11. Incremental Memory Controller Error Codes of Machine Check for IA32_MC8_STATUS
Type
MCA error
codes1
Bit No.
Bit Function
Bit Description
0-15
MCACOD
Memory error format: 1MMMCCCC
16
Read ECC error
if 1, ECC occurred on a read
17
RAS ECC error
If 1, ECC occurred on a scrub
18
Write parity error
If 1, bad parity on a write
19
Redundancy loss
if 1, Error in half of redundant memory
20
Reserved
Reserved
21
Memory range error
If 1, Memory access out of range
22
RTID out of range
If 1, Internal ID invalid
23
Address parity error
If 1, bad address parity
24
Byte enable parity
error
If 1, bad enable parity
37-25
Reserved
Reserved
52:38
CORE_ERR_CNT
Corrected error count
56-53
Reserved
Reserved
Model specific errors
Other information
Status register validity
indicators1
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
Vol. 3B 16-9
INTERPRETING MACHINE-CHECK ERROR CODES
Table 16-12. Incremental Memory Controller Error Codes of Machine Check for IA32_MC8_MISC
Type
Model specific
Bit No.
Bit Function
Bit Description
7-0
RTId
Transaction Tracker ID
15-8
Reserved
Reserved
17-16
DIMM
DIMM ID which got the error
19-18
Channel
Channel ID which got the error
31-20
Reserved
Reserved
63-32
Syndrome
ECC Syndrome
errors1
NOTES:
1. Which of these fields are valid depends on the error type.
16.4
INCREMENTAL DECODING INFORMATION: PROCESSOR FAMILY WITH CPUID
DISPLAYFAMILY_DISPLAYMODEL SIGNATURE 06_2DH, MACHINE ERROR
CODES FOR MACHINE CHECK
Table 16-13 through Table 16-15 provide information for interpreting additional model-specific fields for memory
controller errors relating to the processor family with CPUID DisplayFamily_DisplaySignature 06_2DH, which
supports Intel QuickPath Interconnect links. Incremental MC error codes related to the Intel QPI links are reported
in the register banks IA32_MC6 and IA32_MC7, incremental error codes for internal machine check error from PCU
controller is reported in the register bank IA32_MC4, and incremental error codes for the memory controller unit is
reported in the register banks IA32_MC8-IA32_MC11.
16.4.1
Internal Machine Check Errors
Table 16-13. Machine Check Error Codes for IA32_MC4_STATUS
Type
Bit No.
Bit Function
MCA error
codes1
0-15
MCACOD
Model specific
errors
19:16
Reserved except for
the following
Bit Description
0000b - No Error
0001b - Non_IMem_Sel
0010b - I_Parity_Error
0011b - Bad_OpCode
0100b - I_Stack_Underflow
0101b - I_Stack_Overflow
0110b - D_Stack_Underflow
0111b - D_Stack_Overflow
1000b - Non-DMem_Sel
1001b - D_Parity_Error
16-10 Vol. 3B
INTERPRETING MACHINE-CHECK ERROR CODES
Type
Bit No.
Bit Function
Bit Description
23-20
Reserved
Reserved
31-24
Reserved except for
the following
00h - No Error
0Dh - MC_IMC_FORCE_SR_S3_TIMEOUT
0Eh - MC_CPD_UNCPD_ST_TIMEOUT
0Fh - MC_PKGS_SAFE_WP_TIMEOUT
43h - MC_PECI_MAILBOX_QUIESCE_TIMEOUT
5Ch - MC_MORE_THAN_ONE_LT_AGENT
60h - MC_INVALID_PKGS_REQ_PCH
61h - MC_INVALID_PKGS_REQ_QPI
62h - MC_INVALID_PKGS_RES_QPI
63h - MC_INVALID_PKGC_RES_PCH
64h - MC_INVALID_PKG_STATE_CONFIG
70h - MC_WATCHDG_TIMEOUT_PKGC_SLAVE
71h - MC_WATCHDG_TIMEOUT_PKGC_MASTER
72h - MC_WATCHDG_TIMEOUT_PKGS_MASTER
7ah - MC_HA_FAILSTS_CHANGE_DETECTED
81h - MC_RECOVERABLE_DIE_THERMAL_TOO_HOT
56-32
Status register
validity
indicators1
Reserved
Reserved
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
16.4.2
Intel QPI Machine Check Errors
Table 16-14. Intel QPI MC Error Codes for IA32_MC6_STATUS and IA32_MC7_STATUS
Type
Bit No.
Bit Function
Bit Description
MCA error
codes1
0-15
MCACOD
Bus error format: 1PPTRRRRIILL
56-16
Reserved
Reserved
Model specific
errors
Status register
validity
indicators1
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
16.4.3
Integrated Memory Controller Machine Check Errors
MC error codes associated with integrated memory controllers are reported in the MSRs IA32_MC8_STATUSIA32_MC11_STATUS. The supported error codes are follows the architectural MCACOD definition type 1MMMCCCC
(see Chapter 15, “Machine-Check Architecture,”). MSR_ERROR_CONTROL.[bit 1] can enable additional informaVol. 3B 16-11
INTERPRETING MACHINE-CHECK ERROR CODES
tion logging of the IMC. The additional error information logged by the IMC is stored in IA32_MCi_STATUS and
IA32_MCi_MISC; (i = 8, 11).
Table 16-15. Intel IMC MC Error Codes for IA32_MCi_STATUS (i= 8, 11)
Type
Bit No.
Bit Function
Bit Description
0-15
MCACOD
Bus error format: 1PPTRRRRIILL
Model specific
errors
31:16
Reserved except for
the following
001H - Address parity error
002H - HA Wrt buffer Data parity error
004H - HA Wrt byte enable parity error
008H - Corrected patrol scrub error
010H - Uncorrected patrol scrub error
020H - Corrected spare error
040H - Uncorrected spare error
Model specific
errors
36-32
Other info
When MSR_ERROR_CONTROL.[1] is set, allows the iMC to log first device
error when corrected error is detected during normal read.
37
Reserved
Reserved
MCA error
codes1
56-38
Status register
validity indicators1
See Chapter 15, “Machine-Check Architecture,”
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
Table 16-16. Intel IMC MC Error Codes for IA32_MCi_MISC (i= 8, 11)
Type
Bit No.
MCA addr info1
Bit Function
Bit Description
0-8
See Chapter 15, “Machine-Check Architecture,”
Model specific
errors
13:9
• When MSR_ERROR_CONTROL.[1] is set, allows the iMC to log second device
error when corrected error is detected during normal read.
• Otherwise contain parity error if MCi_Status indicates HA_WB_Data or
HA_W_BE parity error.
Model specific
errors
29-14
ErrMask_1stErrDev
When MSR_ERROR_CONTROL.[1] is set, allows the iMC to log first-device error bit
mask.
Model specific
errors
45-30
ErrMask_2ndErrDev
When MSR_ERROR_CONTROL.[1] is set, allows the iMC to log second-device error
bit mask.
50:46
FailRank_1stErrDev
When MSR_ERROR_CONTROL.[1] is set, allows the iMC to log first-device error
failing rank.
55:51
FailRank_2ndErrDev
When MSR_ERROR_CONTROL.[1] is set, allows the iMC to log second-device error
failing rank.
58:56
Reserved
Reserved
61-59
Reserved
Reserved
62
Valid_1stErrDev
When MSR_ERROR_CONTROL.[1] is set, indicates the iMC has logged valid data
from the first correctable error in a memory device.
63
Valid_2ndErrDev
When MSR_ERROR_CONTROL.[1] is set, indicates the iMC has logged valid data due
to a second correctable error in a memory device. Use this information only after
there is valid first error info indicated by bit 62.
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
16-12 Vol. 3B
INTERPRETING MACHINE-CHECK ERROR CODES
16.5
INCREMENTAL DECODING INFORMATION: PROCESSOR FAMILY WITH
CPUID DISPLAYFAMILY_DISPLAYMODEL SIGNATURE 06_3EH, MACHINE
ERROR CODES FOR MACHINE CHECK
Intel Xeon processor E5 v2 family and Intel Xeon processor E7 v2 family are based on the Ivy Bridge-EP microarchitecture and can be identified with CPUID DisplayFamily_DisplaySignature 06_3EH. Incremental error codes for
internal machine check error from PCU controller is reported in the register bank IA32_MC4, Table lists modelspecific fields to interpret error codes applicable to IA32_MC4_STATUS. Incremental MC error codes related to the
Intel QPI links are reported in the register banks IA32_MC5. Information listed in Table 16-14 for QPI MC error code
apply to IA32_MC5_STATUS. Incremental error codes for the memory controller unit is reported in the register
banks IA32_MC9-IA32_MC16. Table 16-18 lists model-specific error codes apply to IA32_MCi_STATUS, i = 9-16.
16.5.1
Internal Machine Check Errors
Table 16-17. Machine Check Error Codes for IA32_MC4_STATUS
Type
MCA error
codes1
Model specific errors
Bit No.
Bit Function
0-15
MCACOD
19:16
Reserved except for
the following
Bit Description
0000b - No Error
0001b - Non_IMem_Sel
0010b - I_Parity_Error
0011b - Bad_OpCode
0100b - I_Stack_Underflow
0101b - I_Stack_Overflow
0110b - D_Stack_Underflow
0111b - D_Stack_Overflow
1000b - Non-DMem_Sel
1001b - D_Parity_Error
23-20
Reserved
Reserved
31-24
Reserved except for
the following
00h - No Error
0Dh - MC_IMC_FORCE_SR_S3_TIMEOUT
0Eh - MC_CPD_UNCPD_ST_TIMEOUT
0Fh - MC_PKGS_SAFE_WP_TIMEOUT
43h - MC_PECI_MAILBOX_QUIESCE_TIMEOUT
44h - MC_CRITICAL_VR_FAILED
45h - MC_ICC_MAX-NOTSUPPORTED
5Ch - MC_MORE_THAN_ONE_LT_AGENT
60h - MC_INVALID_PKGS_REQ_PCH
61h - MC_INVALID_PKGS_REQ_QPI
62h - MC_INVALID_PKGS_RES_QPI
63h - MC_INVALID_PKGC_RES_PCH
64h - MC_INVALID_PKG_STATE_CONFIG
70h - MC_WATCHDG_TIMEOUT_PKGC_SLAVE
71h - MC_WATCHDG_TIMEOUT_PKGC_MASTER
72h - MC_WATCHDG_TIMEOUT_PKGS_MASTER
Vol. 3B 16-13
INTERPRETING MACHINE-CHECK ERROR CODES
Type
Bit No.
Bit Function
Bit Description
7Ah - MC_HA_FAILSTS_CHANGE_DETECTED
7Bh - MC_PCIE_R2PCIE-RW_BLOCK_ACK_TIMEOUT
81h - MC_RECOVERABLE_DIE_THERMAL_TOO_HOT
56-32
Status register
validity indicators1
Reserved
Reserved
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
16.5.2
Integrated Memory Controller Machine Check Errors
MC error codes associated with integrated memory controllers are reported in the MSRs IA32_MC9_STATUSIA32_MC16_STATUS. The supported error codes are follows the architectural MCACOD definition type 1MMMCCCC
(see Chapter 15, “Machine-Check Architecture,”).
MSR_ERROR_CONTROL.[bit 1] can enable additional information logging of the IMC. The additional error information logged by the IMC is stored in IA32_MCi_STATUS and IA32_MCi_MISC; (i = 9-16).
Table 16-18. Intel IMC MC Error Codes for IA32_MCi_STATUS (i= 9-16)
Type
MCA error
codes1
Model specific
errors
Bit No.
Bit Function
Bit Description
0-15
MCACOD
Memory Controller error format: 000F 0000 1MMM CCCC
31:16
Reserved except for
the following
001H - Address parity error
002H - HA Wrt buffer Data parity error
004H - HA Wrt byte enable parity error
008H - Corrected patrol scrub error
010H - Uncorrected patrol scrub error
020H - Corrected spare error
040H - Uncorrected spare error
080H - Corrected memory read error. (Only applicable with iMC’s “Additional
Error logging” Mode-1 enabled.)
100H - iMC, WDB, parity errors
36-32
Other info
When MSR_ERROR_CONTROL.[1] is set, logs an encoded value from the first error
device.
37
56-38
Status register
validity indicators1
Reserved
Reserved
See Chapter 15, “Machine-Check Architecture,”
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
16-14 Vol. 3B
INTERPRETING MACHINE-CHECK ERROR CODES
Table 16-19. Intel IMC MC Error Codes for IA32_MCi_MISC (i= 9-16)
Type
Bit No.
MCA addr info1
0-8
Bit Function
See Chapter 15, “Machine-Check Architecture,”
Model specific
errors
13:9
If the error logged is MCWrDataPar error or MCWrBEPar error, this field is the WDB
ID that has the parity error. OR if the second error logged is a correctable read
error, MC logs the second error device in this field.
Model specific
errors
29-14
ErrMask_1stErrDev
When MSR_ERROR_CONTROL.[1] is set, allows the iMC to log first-device error bit
mask.
Model specific
errors
45-30
ErrMask_2ndErrDev
When MSR_ERROR_CONTROL.[1] is set, allows the iMC to log second-device error
bit mask.
50:46
FailRank_1stErrDev
When MSR_ERROR_CONTROL.[1] is set, allows the iMC to log first-device error
failing rank.
55:51
FailRank_2ndErrDev
When MSR_ERROR_CONTROL.[1] is set, allows the iMC to log second-device error
failing rank.
61:56
Bit Description
Reserved
62
Valid_1stErrDev
When MSR_ERROR_CONTROL.[1] is set, indicates the iMC has logged valid data
from a correctable error from memory read associated with first error device.
63
Valid_2ndErrDev
When MSR_ERROR_CONTROL.[1] is set, indicates the iMC has logged valid data due
to a second correctable error in a memory device. Use this information only after
there is valid first error info indicated by bit 62.
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
16.6
INCREMENTAL DECODING INFORMATION: PROCESSOR FAMILY WITH
CPUID DISPLAYFAMILY_DISPLAYMODEL SIGNATURE 06_3FH, MACHINE
ERROR CODES FOR MACHINE CHECK
Intel Xeon processor E5 v3 family is based on the Haswell-E microarchitecture and can be identified with CPUID
DisplayFamily_DisplaySignature 06_3FH. Incremental error codes for internal machine check error from PCU
controller is reported in the register bank IA32_MC4, Table 16-20 lists model-specific fields to interpret error codes
applicable to IA32_MC4_STATUS. Incremental MC error codes related to the Intel QPI links are reported in the
register banks IA32_MC5, IA32_MC20, and IA32_MC21. Information listed in Table 16-21 for QPI MC error codes.
Incremental error codes for the memory controller unit is reported in the register banks IA32_MC9-IA32_MC16.
Table 16-22 lists model-specific error codes apply to IA32_MCi_STATUS, i = 9-16.
Vol. 3B 16-15
INTERPRETING MACHINE-CHECK ERROR CODES
16.6.1
Internal Machine Check Errors
Table 16-20. Machine Check Error Codes for IA32_MC4_STATUS
Type
1
MCA error codes
2
MCACOD
Bit No.
Bit Function
15:0
MCACOD
15:0
internal Errors
Bit Description
0402h - PCU internal Errors
0403h - PCU internal Errors
0406h - Intel TXT Errors
0407h - Other UBOX internal Errors.
On an IERR caused by a core 3-strike the IA32_MC3_STATUS (MLC) is copied
to the IA32_MC4_STATUS (After a 3-strike, the core MCA banks will be
unavailable).
Model specific errors
19:16
Reserved except for
the following
0000b - No Error
23-20
Reserved
Reserved
31-24
Reserved except for
the following
00h - No Error
00xxb - PCU internal error
09h - MC_MESSAGE_CHANNEL_TIMEOUT
13h - MC_DMI_TRAINING_TIMEOUT
15h - MC_DMI_CPU_RESET_ACK_TIMEOUT
1Eh - MC_VR_ICC_MAX_LT_FUSED_ICC_MAX
25h - MC_SVID_COMMAND_TIMEOUT
29h - MC_VR_VOUT_MAC_LT_FUSED_SVID
2Bh - MC_PKGC_WATCHDOG_HANG_CBZ_DOWN
2Ch - MC_PKGC_WATCHDOG_HANG_CBZ_UP
44h - MC_CRITICAL_VR_FAILED
46h - MC_VID_RAMP_DOWN_FAILED
49h - MC_SVID_WRITE_REG_VOUT_MAX_FAILED
4Bh - MC_BOOT_VID_TIMEOUT. Timeout setting boot VID for DRAM 0.
4Fh - MC_SVID_COMMAND_ERROR.
52h - MC_FIVR_CATAS_OVERVOL_FAULT.
53h - MC_FIVR_CATAS_OVERCUR_FAULT.
57h - MC_SVID_PKGC_REQUEST_FAILED
58h - MC_SVID_IMON_REQUEST_FAILED
59h - MC_SVID_ALERT_REQUEST_FAILED
62h - MC_INVALID_PKGS_RSP_QPI
64h - MC_INVALID_PKG_STATE_CONFIG
67h - MC_HA_IMC_RW_BLOCK_ACK_TIMEOUT
6Ah - MC_MSGCH_PMREQ_CMP_TIMEOUT
72h - MC_WATCHDG_TIMEOUT_PKGS_MASTER
81h - MC_RECOVERABLE_DIE_THERMAL_TOO_HOT
56-32
Status register
validity indicators1
Reserved
Reserved
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
16-16 Vol. 3B
INTERPRETING MACHINE-CHECK ERROR CODES
2. The internal error codes may be model-specific.
16.6.2
Intel QPI Machine Check Errors
MC error codes associated with the Intel QPI agents are reported in the MSRs IA32_MC5_STATUS,
IA32_MC20_STATUS, and IA32_MC21_STATUS. The supported error codes follow the architectural MCACOD definition type 1PPTRRRRIILL (see Chapter 15, “Machine-Check Architecture,”).
Table 16-21 lists model-specific fields to interpret error codes applicable to IA32_MC5_STATUS,
IA32_MC20_STATUS, and IA32_MC21_STATUS.
Table 16-21. Intel QPI MC Error Codes for IA32_MCi_STATUS (i = 5, 20, 21)
Type
Bit No.
Bit Function
Bit Description
MCA error
codes1
0-15
MCACOD
Bus error format: 1PPTRRRRIILL
Model specific
errors
31-16
MSCOD
02h - Intel QPI physical layer detected drift buffer alarm.
03h - Intel QPI physical layer detected latency buffer rollover.
10h - Intel QPI link layer detected control error from R3QPI.
11h - Rx entered LLR abort state on CRC error.
12h - Unsupported or undefined packet.
13h - Intel QPI link layer control error.
15h - RBT used un-initialized value.
20h - Intel QPI physical layer detected a QPI in-band reset but aborted initialization
21h - Link failover data self-healing
22h - Phy detected in-band reset (no width change).
23h - Link failover clock failover
30h -Rx detected CRC error - successful LLR after Phy re-init.
31h -Rx detected CRC error - successful LLR without Phy re-init.
All other values are reserved.
Status register
validity
indicators1
37-32
Reserved
52-38
Corrected Error Cnt
56-53
Reserved
Reserved
Reserved
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
16.6.3
Integrated Memory Controller Machine Check Errors
MC error codes associated with integrated memory controllers are reported in the MSRs IA32_MC9_STATUSIA32_MC16_STATUS. The supported error codes follow the architectural MCACOD definition type 1MMMCCCC (see
Chapter 15, “Machine-Check Architecture,”).
MSR_ERROR_CONTROL.[bit 1] can enable additional information logging of the IMC. The additional error information logged by the IMC is stored in IA32_MCi_STATUS and IA32_MCi_MISC; (i = 9-16).
Vol. 3B 16-17
INTERPRETING MACHINE-CHECK ERROR CODES
Table 16-22. Intel IMC MC Error Codes for IA32_MCi_STATUS (i= 9-16)
Type
Bit No.
Bit Function
Bit Description
MCA error codes1
0-15
MCACOD
Memory Controller error format: 0000 0000 1MMM CCCC
Model specific
errors
31:16
Reserved except for
the following
0001H - DDR3 address parity error
0002H - Uncorrected HA write data error
0004H - Uncorrected HA data byte enable error
0008H - Corrected patrol scrub error
0010H - Uncorrected patrol scrub error
0020H - Corrected spare error
0040H - Uncorrected spare error
0080H - Corrected memory read error. (Only applicable with iMC’s “Additional
Error logging” Mode-1 enabled.)
0100H - iMC, write data buffer parity errors
0200H - DDR4 command address parity error
36-32
Other info
When MSR_ERROR_CONTROL.[1] is set, logs an encoded value from the first error
device.
37
Reserved
56-38
Status register
validity indicators1
Reserved
See Chapter 15, “Machine-Check Architecture,”
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
Table 16-23. Intel IMC MC Error Codes for IA32_MCi_MISC (i= 9-16)
Type
Bit No.
MCA addr info1
Bit Function
0-8
See Chapter 15, “Machine-Check Architecture,”
Model specific
errors
13:9
If the error logged is MCWrDataPar error or MCWrBEPar error, this field is the WDB
ID that has the parity error. OR if the second error logged is a correctable read
error, MC logs the second error device in this field.
Model specific
errors
29-14
ErrMask_1stErrDev
When MSR_ERROR_CONTROL.[1] is set, allows the iMC to log first-device error bit
mask.
Model specific
errors
45-30
ErrMask_2ndErrDev
When MSR_ERROR_CONTROL.[1] is set, allows the iMC to log second-device error
bit mask.
50:46
FailRank_1stErrDev
When MSR_ERROR_CONTROL.[1] is set, allows the iMC to log first-device error
failing rank.
55:51
FailRank_2ndErrDev
When MSR_ERROR_CONTROL.[1] is set, allows the iMC to log second-device error
failing rank.
61:56
16-18 Vol. 3B
Bit Description
Reserved
62
Valid_1stErrDev
When MSR_ERROR_CONTROL.[1] is set, indicates the iMC has logged valid data
from a correctable error from memory read associated with first error device.
63
Valid_2ndErrDev
When MSR_ERROR_CONTROL.[1] is set, indicates the iMC has logged valid data due
to a second correctable error in a memory device. Use this information only after
there is valid first error info indicated by bit 62.
INTERPRETING MACHINE-CHECK ERROR CODES
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
16.7
INCREMENTAL DECODING INFORMATION: PROCESSOR FAMILY WITH
CPUID DISPLAYFAMILY_DISPLAYMODEL SIGNATURE 06_56H, MACHINE
ERROR CODES FOR MACHINE CHECK
Intel Xeon processor D family is based on the Broadwell microarchitecture and can be identified with CPUID
DisplayFamily_DisplaySignature 06_56H. Incremental error codes for internal machine check error from PCU
controller is reported in the register bank IA32_MC4, Table 16-24 lists model-specific fields to interpret error codes
applicable to IA32_MC4_STATUS. Incremental error codes for the memory controller unit is reported in the register
banks IA32_MC9-IA32_MC10. Table 16-18 lists model-specific error codes apply to IA32_MCi_STATUS, i = 9-10.
16.7.1
Internal Machine Check Errors
Table 16-24. Machine Check Error Codes for IA32_MC4_STATUS
Type
MCA error
codes1
MCACOD2
Bit No.
Bit Function
15:0
MCACOD
15:0
internal Errors
Bit Description
0402h - PCU internal Errors
0403h - internal Errors
0406h - Intel TXT Errors
0407h - Other UBOX internal Errors.
On an IERR caused by a core 3-strike the IA32_MC3_STATUS (MLC) is copied
to the IA32_MC4_STATUS (After a 3-strike, the core MCA banks will be
unavailable).
Model specific errors
19:16
Reserved except for
the following
0000b - No Error
00x1b - PCU internal error
001xb - PCU internal error
23-20
Reserved except for
the following
x1xxb - UBOX error
31-24
Reserved except for
the following
00h - No Error
09h - MC_MESSAGE_CHANNEL_TIMEOUT
13h - MC_DMI_TRAINING_TIMEOUT
15h - MC_DMI_CPU_RESET_ACK_TIMEOUT
1Eh - MC_VR_ICC_MAX_LT_FUSED_ICC_MAX
25h - MC_SVID_COMMAND_TIMEOUT
26h - MCA_PKGC_DIRECT_WAKE_RING_TIMEOUT
29h - MC_VR_VOUT_MAC_LT_FUSED_SVID
2Bh - MC_PKGC_WATCHDOG_HANG_CBZ_DOWN
2Ch - MC_PKGC_WATCHDOG_HANG_CBZ_UP
44h - MC_CRITICAL_VR_FAILED
46h - MC_VID_RAMP_DOWN_FAILED
49h - MC_SVID_WRITE_REG_VOUT_MAX_FAILED
Vol. 3B 16-19
INTERPRETING MACHINE-CHECK ERROR CODES
Type
Bit No.
Bit Function
Bit Description
4Bh - MC_PP1_BOOT_VID_TIMEOUT. Timeout setting boot VID for DRAM 0.
4Fh - MC_SVID_COMMAND_ERROR.
52h - MC_FIVR_CATAS_OVERVOL_FAULT.
53h - MC_FIVR_CATAS_OVERCUR_FAULT.
57h - MC_SVID_PKGC_REQUEST_FAILED
58h - MC_SVID_IMON_REQUEST_FAILED
59h - MC_SVID_ALERT_REQUEST_FAILED
62h - MC_INVALID_PKGS_RSP_QPI
64h - MC_INVALID_PKG_STATE_CONFIG
67h - MC_HA_IMC_RW_BLOCK_ACK_TIMEOUT
6Ah - MC_MSGCH_PMREQ_CMP_TIMEOUT
72h - MC_WATCHDG_TIMEOUT_PKGS_MASTER
81h - MC_RECOVERABLE_DIE_THERMAL_TOO_HOT
56-32
Status register
validity indicators1
Reserved
Reserved
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
2. The internal error codes may be model-specific.
16.7.2
Integrated Memory Controller Machine Check Errors
MC error codes associated with integrated memory controllers are reported in the MSRs IA32_MC9_STATUSIA32_MC10_STATUS. The supported error codes follow the architectural MCACOD definition type 1MMMCCCC (see
Chapter 15, “Machine-Check Architecture,”).
MSR_ERROR_CONTROL.[bit 1] can enable additional information logging of the IMC. The additional error information logged by the IMC is stored in IA32_MCi_STATUS and IA32_MCi_MISC; (i = 9-10).
Table 16-25. Intel IMC MC Error Codes for IA32_MCi_STATUS (i= 9-10)
Type
MCA error
codes1
Model specific
errors
Bit No.
Bit Function
Bit Description
0-15
MCACOD
Memory Controller error format: 0000 0000 1MMM CCCC
31:16
Reserved except for
the following
0001H - DDR3 address parity error
0002H - Uncorrected HA write data error
0004H - Uncorrected HA data byte enable error
0008H - Corrected patrol scrub error
0010H - Uncorrected patrol scrub error
0100H - iMC, write data buffer parity errors
0200H - DDR4 command address parity error
36-32
Other info
Reserved
37
Reserved
Reserved
56-38
Status register
validity indicators1
16-20 Vol. 3B
57-63
See Chapter 15, “Machine-Check Architecture,”
INTERPRETING MACHINE-CHECK ERROR CODES
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
16.8
INCREMENTAL DECODING INFORMATION: PROCESSOR FAMILY WITH
CPUID DISPLAYFAMILY_DISPLAYMODEL SIGNATURE 06_4FH, MACHINE
ERROR CODES FOR MACHINE CHECK
Next Generation Intel Xeon processor E5 family is based on the Broadwell microarchitecture and can be identified
with CPUID DisplayFamily_DisplaySignature 06_4FH. Incremental error codes for internal machine check error
from PCU controller is reported in the register bank IA32_MC4, Table 16-20 in Section 16.6.1lists model-specific
fields to interpret error codes applicable to IA32_MC4_STATUS.
Incremental MC error codes related to the Intel QPI links are reported in the register banks IA32_MC5,
IA32_MC20, and IA32_MC21. Information listed in Table 16-21 of Section 16.6.1 covers QPI MC error codes.
16.8.1
Integrated Memory Controller Machine Check Errors
MC error codes associated with integrated memory controllers are reported in the MSRs IA32_MC9_STATUSIA32_MC16_STATUS. The supported error codes follow the architectural MCACOD definition type 1MMMCCCC (see
Chapter 15, “Machine-Check Architecture,”).
Table 16-26 lists model-specific error codes apply to IA32_MCi_STATUS, i = 9-16.
Table 16-26. Intel IMC MC Error Codes for IA32_MCi_STATUS (i= 9-16)
Type
MCA error
codes1
Model specific
errors
Bit No.
Bit Function
Bit Description
0-15
MCACOD
Memory Controller error format: 0000 0000 1MMM CCCC
31:16
Reserved except for
the following
0001H - DDR3 address parity error
0002H - Uncorrected HA write data error
0004H - Uncorrected HA data byte enable error
0008H - Corrected patrol scrub error
0010H - Uncorrected patrol scrub error
0020H - Corrected spare error
0040H - Uncorrected spare error
0100H - iMC, write data buffer parity errors
0200H - DDR4 command address parity error
36-32
Other info
Reserved
37
Reserved
Reserved
56-38
Status register
validity indicators1
See Chapter 15, “Machine-Check Architecture,”
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
Vol. 3B 16-21
INTERPRETING MACHINE-CHECK ERROR CODES
16.9
INCREMENTAL DECODING INFORMATION: PROCESSOR FAMILY WITH CPUID
DISPLAYFAMILY_DISPLAYMODEL SIGNATURE 06_55H, MACHINE ERROR
CODES FOR MACHINE CHECK
Future Intel Xeon processors with CPUID DisplayFamily_DisplaySignature 06_55H. Incremental error codes for
internal machine check error from PCU controller is reported in the register bank IA32_MC4, Table 16-27 in Section
16.9.1 lists model-specific fields to interpret error codes applicable to IA32_MC4_STATUS.
16.9.1
Internal Machine Check Errors
Table 16-27. Machine Check Error Codes for IA32_MC4_STATUS
Type
Bit No.
Bit Function
MCA error codes
15:0
MCACOD
MCACOD2
15:0
internal Errors
1
Bit Description
0402h - PCU internal Errors
0403h - PCU internal Errors
0406h - Intel TXT Errors
0407h - Other UBOX internal Errors.
On an IERR caused by a core 3-strike the IA32_MC3_STATUS (MLC) is copied
to the IA32_MC4_STATUS (After a 3-strike, the core MCA banks will be
unavailable).
Model specific errors
19:16
Reserved except for
the following
0000b - No Error
23-20
Reserved
Reserved
31-24
Reserved except for
the following
00h - No Error
00xxb - PCU internal error
0Dh - MCA_DMI_TRAINING_TIMEOUT
0Fh - MCA_DMI_CPU_RESET_ACK_TIMEOUT
10h - MCA_MORE_THAN_ONE_LT_AGENT
1Eh - MCA_BIOS_RST_CPL_INVALID_SEQ
1Fh - MCA_BIOS_INVALID_PKG_STATE_CONFIG
25h - MCA_MESSAGE_CHANNEL_TIMEOUT
27h - MCA_MSGCH_PMREQ_CMP_TIMEOUT
30h - MCA_PKGC_DIRECT_WAKE_RING_TIMEOUT
31h - MCA_PKGC_INVALID_RSP_PCH
33h - MCA_PKGC_WATCHDOG_HANG_CBZ_DOWN
34h - MCA_PKGC_WATCHDOG_HANG_CBZ_UP
38h - MCA_PKGC_WATCHDOG_HANG_C3_UP_SF
40h - MCA_SVID_VCCIN_VR_ICC_MAX_FAILURE
41h - MCA_SVID_COMMAND_TIMEOUT
42h - MCA_SVID_VCCIN_VR_VOUT_MAX_FAILURE
43h - MCA_SVID_CPU_VR_CAPABILITY_ERROR
44h - MCA_SVID_CRITICAL_VR_FAILED
45h - MCA_SVID_SA_ITD_ERROR
46h - MCA_SVID_READ_REG_FAILED
47h - MCA_SVID_WRITE_REG_FAILED
48h - MCA_SVID_PKGC_INIT_FAILED
16-22 Vol. 3B
INTERPRETING MACHINE-CHECK ERROR CODES
Type
Bit No.
Bit Function
Bit Description
49h - MCA_SVID_PKGC_CONFIG_FAILED
4Ah - MCA_SVID_PKGC_REQUEST_FAILED
4Bh - MCA_SVID_IMON_REQUEST_FAILED
4Ch - MCA_SVID_ALERT_REQUEST_FAILED
4Dh - MCA_SVID_MCP_VP_ABSENT_OR_RAMP_ERROR
4Eh - MCA_SVID_UNEXPECTED_MCP_VP_DETECTED
51h - MCA_FIVR_CATAS_OVERVOL_FAULT
52h - MCA_FIVR_CATAS_OVERCUR_FAULT
58h - MCA_WATCHDG_TIMEOUT_PKGC_SLAVE
59h - MCA_WATCHDG_TIMEOUT_PKGC_MASTER
5Ah - MCA_WATCHDG_TIMEOUT_PKGS_MASTER
61h - MCA_PKGS_CPD_UNPCD_TIMEOUT
63h - MCA_PKGS_INVALID_REQ_PCH
64h - MCA_PKGS_INVALID_REQ_INTERNAL
65h - MCA_PKGS_INVALID_RSP_INTERNAL
6Bh - MCA_PKGS_SMBUS_VPP_PAUSE_TIMEOUT
81h - MC_RECOVERABLE_DIE_THERMAL_TOO_HOT
Status register
validity indicators1
52-32
Reserved
Reserved
54-53
CORR_ERR_STATUS
Reserved
56-55
Reserved
Reserved
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
2. The internal error codes may be model-specific.
16.9.2
Interconnect Machine Check Errors
MC error codes associated with the link interconnect agents are reported in the MSRs IA32_MC5_STATUS,
IA32_MC12_STATUS, IA32_MC19_STATUS. The supported error codes follow the architectural MCACOD definition
type 1PPTRRRRIILL (see Chapter 15, “Machine-Check Architecture”).
Table 16-28 lists model-specific fields to interpret error codes applicable to IA32_MCi_STATUS, i= 5, 12, 19.
Vol. 3B 16-23
INTERPRETING MACHINE-CHECK ERROR CODES
Table 16-28. Interconnect MC Error Codes for IA32_MCi_STATUS, i = 5, 12, 19
Type
Bit No.
Bit Function
Bit Description
MCA error
codes1
0-15
MCACOD
Bus error format: 1PPTRRRRIILL
The two supported compound error codes:
- 0x0C0F - Unsupported/Undefined Packet
- 0x0E0F - For all other corrected and uncorrected errors
Model specific
errors
21-16
MSCOD
The encoding of Uncorrectable (UC) errors are:
00h - UC Phy Initialization Failure.
01h - UC Phy detected drift buffer alarm.
02h - UC Phy detected latency buffer rollover.
10h - UC link layer Rx detected CRC error: unsuccessful LLR entered abort state
11h - UC LL Rx unsupported or undefined packet.
12h - UC LL or Phy control error.
13h - UC LL Rx parameter exchange exception.
1fh - UC LL detected control error from the link-mesh interface
The encoding of correctable (COR) errors are:
20h - COR Phy initialization abort
21h - COR Phy reset
22h - COR Phy lane failure, recovery in x8 width.
23h - COR Phy L0c error corrected without Phy reset
24h - COR Phy L0c error triggering Phy reset
25h - COR Phy L0p exit error corrected with Phy reset
30h - COR LL Rx detected CRC error - successful LLR without Phy re-init.
31h - COR LL Rx detected CRC error - successful LLR with Phy re-init.
All other values are reserved.
31-22
MSCOD_SPARE
The definition below applies to MSCOD 12h (UC LL or Phy Control Errors)
[Bit 22] : Phy Control Error
[Bit 23] : Unexpected Retry.Ack flit
[Bit 24] : Unexpected Retry.Req flit
[Bit 25] : RF parity error
[Bit 26] : Routeback Table error
[Bit 27] : unexpected Tx Protocol flit (EOP, Header or Data)
[Bit 28] : Rx Header-or-Credit BGF credit overflow/underflow
[Bit 29] : Link Layer Reset still in progress when Phy enters L0 (Phy training should
not be enabled until after LL reset is complete as indicated by
KTILCL.LinkLayerReset going back to 0).
[Bit 30] : Link Layer reset initiated while protocol traffic not idle
[Bit 31] : Link Layer Tx Parity Error
Status register
validity
indicators1
16-24 Vol. 3B
37-32
Reserved
52-38
Corrected Error Cnt
56-53
Reserved
57-63
Reserved
Reserved
INTERPRETING MACHINE-CHECK ERROR CODES
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
16.9.3
Integrated Memory Controller Machine Check Errors
MC error codes associated with integrated memory controllers are reported in the MSRs IA32_MC13_STATUSIA32_MC16_STATUS. The supported error codes follow the architectural MCACOD definition type 1MMMCCCC (see
Chapter 15, “Machine-Check Architecture,”).
Table 16-29. Intel IMC MC Error Codes for IA32_MCi_STATUS (i= 13-16)
Type
Bit No.
Bit Function
Bit Description
MCA error codes
0-15
MCACOD
Memory Controller error format: 0000 0000 1MMM CCCC
Model specific
errors
31:16
Reserved except for
the following
0001H - Address parity error
1
0002H - HA write data parity error
0004H - HA write byte enable parity error
0008H - Corrected patrol scrub error
0010H - Uncorrected patrol scrub error
0020H - Corrected spare error
0040H - Uncorrected spare error
0080H - Any HA read error
0100H - WDB read parity error
0200H - DDR4 command address parity error
0400H - Uncorrected address parity error
0800H - Unrecognized request type
0801H - Read response to an invalid scoreboard entry
0802H - Unexpected read response
0803H - DDR4 completion to an invalid scoreboard entry
0804H - Completion to an invalid scoreboard entry
0805H - Completion FIFO overflow
0806H - Correctable parity error
0807H - Uncorrectable error
0808H - Interrupt received while outstanding interrupt was not ACKed
0809H - ERID FIFO overflow
080aH - Error on Write credits
080bH - Error on Read credits
080cH - Scheduler error
080dH - Error event
36-32
Other info
MC logs the first error device. This is an encoded 5-bit value of the device.
37
Reserved
Reserved
56-38
Status register
validity indicators1
See Chapter 15, “Machine-Check Architecture,”
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
Vol. 3B 16-25
INTERPRETING MACHINE-CHECK ERROR CODES
16.9.4
M2M Machine Check Errors
MC error codes associated with M2M are reported in the MSRs IA32_MC7_STATUS, IA32_MC8_STATUS. The
supported error codes follow the architectural MCACOD definition type 1MMMCCCC (see Chapter 15, “MachineCheck Architecture,”).
Table 16-30. M2M MC Error Codes for IA32_MCi_STATUS (i= 7-8)
Type
Bit No.
Bit Function
Bit Description
MCA error codes
0-15
MCACOD
Compound error format: 0000 0000 1MMM CCCC
Model specific
errors
16
MscodDataRdErr
Logged an MC read data error
17
Reserved
Reserved
18
MscodPtlWrErr
Logged an MC partial write data error
19
MscodFullWrErr
Logged a full write data error
20
MscodBgfErr
Logged an M2M clock-domain-crossing buffer (BGF) error
21
MscodTimeOut
Logged an M2M time out
22
MscodParErr
Logged an M2M tracker parity error
23
MscodBucket1Err
Logged a fatal Bucket1 error
31-24
Reserved
Reserved
36-32
Other info
MC logs the first error device. This is an encoded 5-bit value of the device.
37
Reserved
Reserved
1
56-38
Status register
validity indicators1
See Chapter 15, “Machine-Check Architecture,”
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
16.10
INCREMENTAL DECODING INFORMATION: PROCESSOR FAMILY 0FH
MACHINE ERROR CODES FOR MACHINE CHECK
Table 16-31 provides information for interpreting additional family 0FH model-specific fields for external bus errors.
These errors are reported in the IA32_MCi_STATUS MSRs. They are reported architecturally) as compound errors
with a general form of 0000 1PPT RRRR IILL in the MCA error code field. See Chapter 15 for information on the
interpretation of compound error codes.
Table 16-31. Incremental Decoding Information: Processor Family 0FH Machine Error Codes For Machine Check
Type
Bit No. Bit Function
MCA error
codes1
0-15
Model-specific
error codes
16
FSB address parity
Bit Description
Address parity error detected:
1 = Address parity error detected
0 = No address parity error
16-26 Vol. 3B
17
Response hard fail
Hardware failure detected on response
18
Response parity
Parity error detected on response
INTERPRETING MACHINE-CHECK ERROR CODES
Table 16-31. Incremental Decoding Information: Processor Family 0FH Machine Error Codes For Machine Check
Type
Bit No. Bit Function
Bit Description
19
PIC and FSB data parity
Data Parity detected on either PIC or FSB access
20
Processor Signature =
00000F04H: Invalid PIC
request
Processor Signature = 00000F04H. Indicates error due to an invalid PIC
request access was made to PIC space with WB memory):
1 = Invalid PIC request error
0 = No Invalid PIC request error
Reserved
All other processors:
Reserved
Other
Information
21
Pad state machine
The state machine that tracks P and N data-strobe relative timing has
become unsynchronized or a glitch has been detected.
22
Pad strobe glitch
Data strobe glitch
23
Pad address glitch
Address strobe glitch
24-56
Reserved
Reserved
Status register 57-63
validity
indicators1
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
Table 16-10 provides information on interpreting additional family 0FH, model specific fields for cache hierarchy
errors. These errors are reported in one of the IA32_MCi_STATUS MSRs. These errors are reported, architecturally,
as compound errors with a general form of 0000 0001 RRRR TTLL in the MCA error code field. See Chapter 15 for
how to interpret the compound error code.
16.10.1 Model-Specific Machine Check Error Codes for Intel Xeon Processor MP 7100 Series
Intel Xeon processor MP 7100 series has 5 register banks which contains information related to Machine Check
Errors. MCi_STATUS[63:0] refers to all 5 register banks. MC0_STATUS[63:0] through MC3_STATUS[63:0] is the
same as on previous generation of Intel Xeon processors within Family 0FH. MC4_STATUS[63:0] is the main error
logging for the processor’s L3 and front side bus errors. It supports the L3 Errors, Bus and Interconnect Errors
Compound Error Codes in the MCA Error Code Field.
Table 16-32. MCi_STATUS Register Bit Definition
Bit Field Name
Bits
Description
MCA_Error_Code
15:0
Specifies the machine check architecture defined error code for the machine check error condition
detected. The machine check architecture defined error codes are guaranteed to be the same for all
Intel Architecture processors that implement the machine check architecture. See tables below
Model_Specific_E 31:16
rror_Code
Specifies the model specific error code that uniquely identifies the machine check error condition
detected. The model specific error codes may differ among Intel Architecture processors for the same
Machine Check Error condition. See tables below
Other_Info
The functions of the bits in this field are implementation specific and are not part of the machine check
architecture. Software that is intended to be portable among Intel Architecture processors should not
rely on the values in this field.
56:32
Vol. 3B 16-27
INTERPRETING MACHINE-CHECK ERROR CODES
Table 16-32. MCi_STATUS Register Bit Definition (Contd.)
Bit Field Name
Bits
Description
PCC
57
Processor Context Corrupt flag indicates that the state of the processor might have been corrupted by
the error condition detected and that reliable restarting of the processor may not be possible. When
clear, this flag indicates that the error did not affect the processor's state. This bit will always be set for
MC errors which are not corrected.
ADDRV
58
MC_ADDR register valid flag indicates that the MC_ADDR register contains the address where the error
occurred. When clear, this flag indicates that the MC_ADDR register does not contain the address where
the error occurred. The MC_ADDR register should not be read if the ADDRV bit is clear.
MISCV
59
MC_MISC register valid flag indicates that the MC_MISC register contains additional
information regarding the error. When clear, this flag indicates that the MC_MISC register does not
contain additional information regarding the error. MC_MISC should not be read if the MISCV bit is not
set.
EN
60
Error enabled flag indicates that reporting of the machine check exception for this error was enabled by
the associated flag bit of the MC_CTL register. Note that correctable errors do not have associated
enable bits in the MC_CTL register so the EN bit should be clear when a correctable error is logged.
UC
61
Error uncorrected flag indicates that the processor did not correct the error condition. When clear, this
flag indicates that the processor was able to correct the event condition.
OVER
62
Machine check overflow flag indicates that a machine check error occurred while the results of a
previous error were still in the register bank (i.e., the VAL bit was already set in the
MC_STATUS register). The processor sets the OVER flag and software is responsible for clearing it.
Enabled errors are written over disabled errors, and uncorrected errors are written over corrected
events. Uncorrected errors are not written over previous valid uncorrected errors.
VAL
63
MC_STATUS register valid flag indicates that the information within the MC_STATUS register is valid.
When this flag is set, the processor follows the rules given for the OVER flag in the MC_STATUS register
when overwriting previously valid entries. The processor sets the VAL flag and software is responsible
for clearing it.
16.10.1.1 Processor Machine Check Status Register
MCA Error Code Definition
Intel Xeon processor MP 7100 series use compound MCA Error Codes for logging its CBC internal machine check
errors, L3 Errors, and Bus/Interconnect Errors. It defines additional Machine Check error types
(IA32_MC4_STATUS[15:0]) beyond those defined in Chapter 15. Table 16-33 lists these model-specific MCA error
codes. Error code details are specified in MC4_STATUS [31:16] (see Section 16.10.3), the “Model Specific Error
Code” field. The information in the “Other_Info” field (MC4_STATUS[56:32]) is common to the three processor
error types and contains a correctable event count and specifies the MC4_MISC register format.
Table 16-33. Incremental MCA Error Code for Intel Xeon Processor MP 7100
Processor MCA_Error_Code (MC4_STATUS[15:0])
Type
Error Code
Binary Encoding
C
Internal Error
0000 0100 0000 0000 Internal Error Type Code
A
L3 Tag Error
0000 0001 0000 1011 L3 Tag Error Type Code
16-28 Vol. 3B
Meaning
INTERPRETING MACHINE-CHECK ERROR CODES
Table 16-33. Incremental MCA Error Code for Intel Xeon Processor MP 7100 (Contd.)
Processor MCA_Error_Code (MC4_STATUS[15:0])
B
Bus and
Interconnect
0000 100x 0000 1111
Not used but this encoding is reserved for compatibility with other MCA
implementations
Error
0000 101x 0000 1111
Not used but this encoding is reserved for compatibility with other MCA
implementations
0000 110x 0000 1111
Not used but this encoding is reserved for compatibility with other MCA
implementations
0000 1110 0000 1111 Bus and Interconnection Error Type Code
0000 1111 0000 1111 Not used but this encoding is reserved for compatibility with other MCA
implementations
The Bold faced binary encodings are the only encodings used by the processor for MC4_STATUS[15:0].
16.10.2 Other_Info Field (all MCA Error Types)
The MC4_STATUS[56:32] field is common to the processor's three MCA error types (A, B & C).
Table 16-34. Other Information Field Bit Definition
Bit Field Name
Bits
Description
39:32
8-bit Correctable
Event Count
Holds a count of the number of correctable events since cold reset. This is a saturating counter;
the counter begins at 1 (with the first error) and saturates at a count of 255.
41:40
MC4_MISC
format type
The value in this field specifies the format of information in the MC4_MISC register. Currently,
only two values are defined. Valid only when MISCV is asserted.
43:42
–
Reserved
51:44
ECC syndrome
ECC syndrome value for a correctable ECC event when the “Valid ECC syndrome” bit is asserted
52
Valid ECC
syndrome
Set when correctable ECC event supplies the ECC syndrome
54:53
Threshold-Based 00: No tracking - No hardware status tracking is provided for the structure reporting this event.
Error Status
01: Green - Status tracking is provided for the structure posting the event; the current status is
green (below threshold).
10: Yellow - Status tracking is provided for the structure posting the event; the current status is
yellow (above threshold).
11: Reserved for future use
Valid only if Valid bit (bit 63) is set
Undefined if the UC bit (bit 61) is set
56:55
–
Reserved
Vol. 3B 16-29
INTERPRETING MACHINE-CHECK ERROR CODES
16.10.3 Processor Model Specific Error Code Field
16.10.3.1 MCA Error Type A: L3 Error
Note:
The Model Specific Error Code field in MC4_STATUS (bits 31:16).
Table 16-35. Type A: L3 Error Codes
Bit
Num
Sub-Field
Name
Description
Legal Value(s)
18:16
L3 Error
Code
Describes the L3
error
encountered
000 - No error
001 - More than one way reporting a correctable event
010 - More than one way reporting an uncorrectable error
011 - More than one way reporting a tag hit
100 - No error
101 - One way reporting a correctable event
110 - One way reporting an uncorrectable error
111 - One or more ways reporting a correctable event while one or more ways are
reporting an uncorrectable error
20:19
–
Reserved
00
31:21
–
Fixed pattern
0010_0000_000
16.10.3.2 Processor Model Specific Error Code Field Type B: Bus and Interconnect Error
Note:
The Model Specific Error Code field in MC4_STATUS (bits 31:16).
Table 16-36. Type B Bus and Interconnect Error Codes
Bit Num
Sub-Field Name
Description
16
FSB Request Parity
Parity error detected during FSB request phase
17
Core0 Addr Parity
Parity error detected on Core 0 request’s address field
18
Core1 Addr Parity
Parity error detected on Core 1 request’s address field
19
Reserved
20
FSB Response Parity
Parity error on FSB response field detected
21
FSB Data Parity
FSB data parity error on inbound data detected
22
Core0 Data Parity
Data parity error on data received from Core 0 detected
23
Core1 Data Parity
Data parity error on data received from Core 1 detected
24
IDS Parity
Detected an Enhanced Defer parity error (phase A or phase B)
25
FSB Inbound Data ECC
Data ECC event to error on inbound data (correctable or uncorrectable)
26
FSB Data Glitch
Pad logic detected a data strobe ‘glitch’ (or sequencing error)
27
FSB Address Glitch
Pad logic detected a request strobe ‘glitch’ (or sequencing error)
31:28
---
Reserved
Exactly one of the bits defined in the preceding table will be set for a Bus and Interconnect Error. The Data ECC can
be correctable or uncorrectable (the MC4_STATUS.UC bit, of course, distinguishes between correctable and uncorrectable cases with the Other_Info field possibly providing the ECC Syndrome for correctable errors). All other
errors for this processor MCA Error Type are uncorrectable.
16-30 Vol. 3B
INTERPRETING MACHINE-CHECK ERROR CODES
16.10.3.3 Processor Model Specific Error Code Field Type C: Cache Bus Controller Error
Table 16-37. Type C Cache Bus Controller Error Codes
MC4_STATUS[31:16] (MSCE) Value
Error Description
0000_0000_0000_0001 0001H
Inclusion Error from Core 0
0000_0000_0000_0010 0002H
Inclusion Error from Core 1
0000_0000_0000_0011 0003H
Write Exclusive Error from Core 0
0000_0000_0000_0100 0004H
Write Exclusive Error from Core 1
0000_0000_0000_0101 0005H
Inclusion Error from FSB
0000_0000_0000_0110 0006H
SNP Stall Error from FSB
0000_0000_0000_0111 0007H
Write Stall Error from FSB
0000_0000_0000_1000 0008H
FSB Arb Timeout Error
0000_0000_0000_1001 0009H
CBC OOD Queue Underflow/overflow
0000_0001_0000_0000 0100H
Enhanced Intel SpeedStep Technology TM1-TM2 Error
0000_0010_0000_0000 0200H
Internal Timeout error
0000_0011_0000_0000 0300H
Internal Timeout Error
0000_0100_0000_0000 0400H
Intel® Cache Safe Technology Queue Full Error or Disabled-ways-in-a-set overflow
1100_0000_0000_0001 C001H
Correctable ECC event on outgoing FSB data
1100_0000_0000_0010 C002H
Correctable ECC event on outgoing Core 0 data
1100_0000_0000_0100 C004H
Correctable ECC event on outgoing Core 1 data
1110_0000_0000_0001 E001H
Uncorrectable ECC error on outgoing FSB data
1110_0000_0000_0010 E002H
Uncorrectable ECC error on outgoing Core 0 data
1110_0000_0000_0100 E004H
Uncorrectable ECC error on outgoing Core 1 data
— all other encodings —
Reserved
Vol. 3B 16-31
INTERPRETING MACHINE-CHECK ERROR CODES
All errors - except for the correctable ECC types - in this table are uncorrectable. The correctable ECC events may
supply the ECC syndrome in the Other_Info field of the MC4_STATUS MSR.
Table 16-38. Decoding Family 0FH Machine Check Codes for Cache Hierarchy Errors
Type
Bit No.
MCA error
codes1
0-15
Model
specific error
codes
16-17
Bit Function
Bit Description
Tag Error Code
Contains the tag error code for this machine check error:
00 = No error detected
01 = Parity error on tag miss with a clean line
10 = Parity error/multiple tag match on tag hit
11 = Parity error/multiple tag match on tag miss
18-19
Data Error Code
Contains the data error code for this machine check error:
00 = No error detected
01 = Single bit error
10 = Double bit error on a clean line
11 = Double bit error on a modified line
20
L3 Error
This bit is set if the machine check error originated in the L3 it can be ignored for
invalid PIC request errors):
1 = L3 error
0 = L2 error
21
Invalid PIC Request
Indicates error due to invalid PIC request access was made to PIC space with WB
memory):
1 = Invalid PIC request error
0 = No invalid PIC request error
Other
Information
Status
register
validity
indicators1
22-31
Reserved
Reserved
32-39
8-bit Error Count
Holds a count of the number of errors since reset. The counter begins at 0 for the
first error and saturates at a count of 255.
40-56
Reserved
Reserved
57-63
NOTES:
1. These fields are architecturally defined. Refer to Chapter 15, “Machine-Check Architecture,” for more information.
16-32 Vol. 3B
CHAPTER 17
DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING
FEATURES
Intel 64 and IA-32 architectures provide debug facilities for use in debugging code and monitoring performance.
These facilities are valuable for debugging application software, system software, and multitasking operating
systems. Debug support is accessed using debug registers (DR0 through DR7) and model-specific registers
(MSRs):
•
Debug registers hold the addresses of memory and I/O locations called breakpoints. Breakpoints are userselected locations in a program, a data-storage area in memory, or specific I/O ports. They are set where a
programmer or system designer wishes to halt execution of a program and examine the state of the processor
by invoking debugger software. A debug exception (#DB) is generated when a memory or I/O access is made
to a breakpoint address.
•
MSRs monitor branches, interrupts, and exceptions; they record addresses of the last branch, interrupt or
exception taken and the last branch taken before an interrupt or exception.
•
•
Time stamp counter is described in Section 17.15, “Time-Stamp Counter”.
•
Features which enable control over shared platform resources are described in Section 17.17, “Intel® Resource
Director Technology (Intel® RDT) Allocation Features”.
Features which allow monitoring of shared platform resources such as the L3 cache are described in Section
17.16, “Intel® Resource Director Technology (Intel® RDT) Monitoring Features”.
17.1
OVERVIEW OF DEBUG SUPPORT FACILITIES
The following processor facilities support debugging and performance monitoring:
•
Debug exception (#DB) — Transfers program control to a debug procedure or task when a debug event
occurs.
•
•
•
Breakpoint exception (#BP) — See breakpoint instruction (INT 3) below.
Breakpoint-address registers (DR0 through DR3) — Specifies the addresses of up to 4 breakpoints.
Debug status register (DR6) — Reports the conditions that were in effect when a debug or breakpoint
exception was generated.
•
Debug control register (DR7) — Specifies the forms of memory or I/O access that cause breakpoints to be
generated.
•
T (trap) flag, TSS — Generates a debug exception (#DB) when an attempt is made to switch to a task with
the T flag set in its TSS.
•
•
RF (resume) flag, EFLAGS register — Suppresses multiple exceptions to the same instruction.
•
Breakpoint instruction (INT 3) — Generates a breakpoint exception (#BP) that transfers program control to
the debugger procedure or task. This instruction is an alternative way to set code breakpoints. It is especially
useful when more than four breakpoints are desired, or when breakpoints are being placed in the source code.
•
Last branch recording facilities — Store branch records in the last branch record (LBR) stack MSRs for the
most recent taken branches, interrupts, and/or exceptions in MSRs. A branch record consist of a branch-from
and a branch-to instruction address. Send branch records out on the system bus as branch trace messages
(BTMs).
TF (trap) flag, EFLAGS register — Generates a debug exception (#DB) after every execution of an
instruction.
These facilities allow a debugger to be called as a separate task or as a procedure in the context of the current
program or task. The following conditions can be used to invoke the debugger:
•
•
Task switch to a specific task.
Execution of the breakpoint instruction.
Vol. 3B 17-1
DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
•
•
•
•
•
•
•
Execution of any instruction.
Execution of an instruction at a specified address.
Read or write to a specified memory address/range.
Write to a specified memory address/range.
Input from a specified I/O address/range.
Output to a specified I/O address/range.
Attempt to change the contents of a debug register.
17.2
DEBUG REGISTERS
Eight debug registers (see Figure 17-1 for 32-bit operation and Figure 17-2 for 64-bit operation) control the debug
operation of the processor. These registers can be written to and read using the move to/from debug register form
of the MOV instruction. A debug register may be the source or destination operand for one of these instructions.
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
LEN R/W LEN R/W LEN R/W LEN R/W 0 0 G 0 R 1 G L G L G L G L G L
DR7
T
3
3
2
2
1
1
0
0
D
E E 3 3 2 2 1 1 0 0
M
31
16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Reserved (set to 1)
R
T B B B 0 1 1 1 1 1 1 1 1 B B B B DR6
3 2 1 0
MT S D
31
0
DR5
31
0
DR4
31
0
DR3
Breakpoint 3 Linear Address
31
0
DR2
Breakpoint 2 Linear Address
31
0
DR1
Breakpoint 1 Linear Address
31
0
Breakpoint 0 Linear Address
Reserved
Figure 17-1. Debug Registers
17-2 Vol. 3B
DR0
DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
Debug registers are privileged resources; a MOV instruction that accesses these registers can only be executed in
real-address mode, in SMM or in protected mode at a CPL of 0. An attempt to read or write the debug registers
from any other privilege level generates a general-protection exception (#GP).
The primary function of the debug registers is to set up and monitor from 1 to 4 breakpoints, numbered 0 though
3. For each breakpoint, the following information can be specified:
•
•
•
•
•
The linear address where the breakpoint is to occur.
The length of the breakpoint location: 1, 2, 4, or 8 bytes (refer to the notes in Section 17.2.4).
The operation that must be performed at the address for a debug exception to be generated.
Whether the breakpoint is enabled.
Whether the breakpoint condition was present when the debug exception was generated.
The following paragraphs describe the functions of flags and fields in the debug registers.
17.2.1
Debug Address Registers (DR0-DR3)
Each of the debug-address registers (DR0 through DR3) holds the 32-bit linear address of a breakpoint (see
Figure 17-1). Breakpoint comparisons are made before physical address translation occurs. The contents of debug
register DR7 further specifies breakpoint conditions.
17.2.2
Debug Registers DR4 and DR5
Debug registers DR4 and DR5 are reserved when debug extensions are enabled (when the DE flag in control
register CR4 is set) and attempts to reference the DR4 and DR5 registers cause invalid-opcode exceptions (#UD).
When debug extensions are not enabled (when the DE flag is clear), these registers are aliased to debug registers
DR6 and DR7.
17.2.3
Debug Status Register (DR6)
The debug status register (DR6) reports debug conditions that were sampled at the time the last debug exception
was generated (see Figure 17-1). Updates to this register only occur when an exception is generated. The flags in
this register show the following information:
•
B0 through B3 (breakpoint condition detected) flags (bits 0 through 3) — Indicates (when set) that its
associated breakpoint condition was met when a debug exception was generated. These flags are set if the
condition described for each breakpoint by the LENn, and R/Wn flags in debug control register DR7 is true.
They may or may not be set if the breakpoint is not enabled by the Ln or the Gn flags in register DR7. Therefore
on a #DB, a debug handler should check only those B0-B3 bits which correspond to an enabled breakpoint.
•
BD (debug register access detected) flag (bit 13) — Indicates that the next instruction in the instruction
stream accesses one of the debug registers (DR0 through DR7). This flag is enabled when the GD (general
detect) flag in debug control register DR7 is set. See Section 17.2.4, “Debug Control Register (DR7),” for
further explanation of the purpose of this flag.
•
BS (single step) flag (bit 14) — Indicates (when set) that the debug exception was triggered by the singlestep execution mode (enabled with the TF flag in the EFLAGS register). The single-step mode is the highestpriority debug exception. When the BS flag is set, any of the other debug status bits also may be set.
•
BT (task switch) flag (bit 15) — Indicates (when set) that the debug exception resulted from a task switch
where the T flag (debug trap flag) in the TSS of the target task was set. See Section 7.2.1, “Task-State
Segment (TSS),” for the format of a TSS. There is no flag in debug control register DR7 to enable or disable this
exception; the T flag of the TSS is the only enabling flag.
•
RTM (restricted transactional memory) flag (bit 16) — Indicates (when clear) that a debug exception
(#DB) or breakpoint exception (#BP) occurred inside an RTM region while advanced debugging of RTM transactional regions was enabled (see Section 17.3.3). This bit is set for any other debug exception (including all
those that occur when advanced debugging of RTM transactional regions is not enabled). This bit is always 1 if
the processor does not support RTM.
Vol. 3B 17-3
DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
Certain debug exceptions may clear bits 0-3. The remaining contents of the DR6 register are never cleared by the
processor. To avoid confusion in identifying debug exceptions, debug handlers should clear the register (except
bit 16, which they should set) before returning to the interrupted task.
17.2.4
Debug Control Register (DR7)
The debug control register (DR7) enables or disables breakpoints and sets breakpoint conditions (see Figure 17-1).
The flags and fields in this register control the following things:
•
L0 through L3 (local breakpoint enable) flags (bits 0, 2, 4, and 6) — Enables (when set) the breakpoint
condition for the associated breakpoint for the current task. When a breakpoint condition is detected and its
associated Ln flag is set, a debug exception is generated. The processor automatically clears these flags on
every task switch to avoid unwanted breakpoint conditions in the new task.
•
G0 through G3 (global breakpoint enable) flags (bits 1, 3, 5, and 7) — Enables (when set) the
breakpoint condition for the associated breakpoint for all tasks. When a breakpoint condition is detected and its
associated Gn flag is set, a debug exception is generated. The processor does not clear these flags on a task
switch, allowing a breakpoint to be enabled for all tasks.
•
LE and GE (local and global exact breakpoint enable) flags (bits 8, 9) — This feature is not supported in
the P6 family processors, later IA-32 processors, and Intel 64 processors. When set, these flags cause the
processor to detect the exact instruction that caused a data breakpoint condition. For backward and forward
compatibility with other Intel processors, we recommend that the LE and GE flags be set to 1 if exact
breakpoints are required.
•
RTM (restricted transactional memory) flag (bit 11) — Enables (when set) advanced debugging of RTM
transactional regions (see Section 17.3.3). This advanced debugging is enabled only if IA32_DEBUGCTL.RTM is
also set.
•
GD (general detect enable) flag (bit 13) — Enables (when set) debug-register protection, which causes a
debug exception to be generated prior to any MOV instruction that accesses a debug register. When such a
condition is detected, the BD flag in debug status register DR6 is set prior to generating the exception. This
condition is provided to support in-circuit emulators.
When the emulator needs to access the debug registers, emulator software can set the GD flag to prevent
interference from the program currently executing on the processor.
The processor clears the GD flag upon entering to the debug exception handler, to allow the handler access to
the debug registers.
•
R/W0 through R/W3 (read/write) fields (bits 16, 17, 20, 21, 24, 25, 28, and 29) — Specifies the
breakpoint condition for the corresponding breakpoint. The DE (debug extensions) flag in control register CR4
determines how the bits in the R/Wn fields are interpreted. When the DE flag is set, the processor interprets
bits as follows:
00
01
10
11
—
—
—
—
Break
Break
Break
Break
on
on
on
on
instruction execution only.
data writes only.
I/O reads or writes.
data reads or writes but not instruction fetches.
When the DE flag is clear, the processor interprets the R/Wn bits the same as for the Intel386™ and Intel486™
processors, which is as follows:
00
01
10
11
•
—
—
—
—
Break on instruction execution only.
Break on data writes only.
Undefined.
Break on data reads or writes but not instruction fetches.
LEN0 through LEN3 (Length) fields (bits 18, 19, 22, 23, 26, 27, 30, and 31) — Specify the size of the
memory location at the address specified in the corresponding breakpoint address register (DR0 through DR3).
These fields are interpreted as follows:
00
01
10
11
17-4 Vol. 3B
—
—
—
—
1-byte length.
2-byte length.
Undefined (or 8 byte length, see note below).
4-byte length.
DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
If the corresponding RWn field in register DR7 is 00 (instruction execution), then the LENn field should also be 00.
The effect of using other lengths is undefined. See Section 17.2.5, “Breakpoint Field Recognition,” below.
NOTES
For Pentium® 4 and Intel® Xeon® processors with a CPUID signature corresponding to family 15
(model 3, 4, and 6), break point conditions permit specifying 8-byte length on data read/write with
an of encoding 10B in the LENn field.
Encoding 10B is also supported in processors based on Intel Core microarchitecture or enhanced
Intel Core microarchitecture, the respective CPUID signatures corresponding to family 6, model 15,
and family 6, DisplayModel value 23 (see CPUID instruction in Chapter 3, “Instruction Set
Reference, A-M” in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume
2A). The Encoding 10B is supported in processors based on Intel® Atom™ microarchitecture, with
CPUID signature of family 6, DisplayModel value 1CH. The encoding 10B is undefined for other
processors.
17.2.5
Breakpoint Field Recognition
Breakpoint address registers (debug registers DR0 through DR3) and the LENn fields for each breakpoint define a
range of sequential byte addresses for a data or I/O breakpoint. The LENn fields permit specification of a 1-, 2-, 4, or 8-byte range, beginning at the linear address specified in the corresponding debug register (DRn). Two-byte
ranges must be aligned on word boundaries; 4-byte ranges must be aligned on doubleword boundaries. I/O
addresses are zero-extended (from 16 to 32 bits, for comparison with the breakpoint address in the selected debug
register). These requirements are enforced by the processor; it uses LENn field bits to mask the lower address bits
in the debug registers. Unaligned data or I/O breakpoint addresses do not yield valid results.
A data breakpoint for reading or writing data is triggered if any of the bytes participating in an access is within the
range defined by a breakpoint address register and its LENn field. Table 17-1 provides an example setup of debug
registers and data accesses that would subsequently trap or not trap on the breakpoints.
A data breakpoint for an unaligned operand can be constructed using two breakpoints, where each breakpoint is
byte-aligned and the two breakpoints together cover the operand. The breakpoints generate exceptions only for
the operand, not for neighboring bytes.
Instruction breakpoint addresses must have a length specification of 1 byte (the LENn field is set to 00). Code
breakpoints for other operand sizes are undefined. The processor recognizes an instruction breakpoint address
only when it points to the first byte of an instruction. If the instruction has prefixes, the breakpoint address must
point to the first prefix.
Table 17-1. Breakpoint Examples
Debug Register Setup
Debug Register
R/Wn
Breakpoint Address
LENn
DR0
DR1
DR2
DR3
R/W0 = 11 (Read/Write)
R/W1 = 01 (Write)
R/W2 = 11 (Read/Write)
R/W3 = 01 (Write)
A0001H
A0002H
B0002H
C0000H
LEN0 = 00 (1 byte)
LEN1 = 00 (1 byte)
LEN2 = 01) (2 bytes)
LEN3 = 11 (4 bytes)
Data Accesses
Operation
Address
Access Length
(In Bytes)
Vol. 3B 17-5
DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
Table 17-1. Breakpoint Examples (Contd.)
Debug Register Setup
Debug Register
Breakpoint Address
LENn
Data operations that trap
- Read or write
- Read or write
- Write
- Write
- Read or write
- Read or write
- Read or write
- Write
- Write
- Write
A0001H
A0001H
A0002H
A0002H
B0001H
B0002H
B0002H
C0000H
C0001H
C0003H
1
2
1
2
4
1
2
4
2
1
Data operations that do not trap
- Read or write
- Read
- Read or write
- Read or write
- Read
- Read or write
A0000H
A0002H
A0003H
B0000H
C0000H
C0004H
1
1
4
2
2
4
17.2.6
R/Wn
Debug Registers and Intel® 64 Processors
For Intel 64 architecture processors, debug registers DR0–DR7 are 64 bits. In 16-bit or 32-bit modes (protected
mode and compatibility mode), writes to a debug register fill the upper 32 bits with zeros. Reads from a debug
register return the lower 32 bits. In 64-bit mode, MOV DRn instructions read or write all 64 bits. Operand-size
prefixes are ignored.
In 64-bit mode, the upper 32 bits of DR6 and DR7 are reserved and must be written with zeros. Writing 1 to any of
the upper 32 bits results in a #GP(0) exception (see Figure 17-2). All 64 bits of DR0–DR3 are writable by software.
However, MOV DRn instructions do not check that addresses written to DR0–DR3 are in the linear-address limits of
the processor implementation (address matching is supported only on valid addresses generated by the processor
implementation). Break point conditions for 8-byte memory read/writes are supported in all modes.
17.3
DEBUG EXCEPTIONS
The Intel 64 and IA-32 architectures dedicate two interrupt vectors to handling debug exceptions: vector 1 (debug
exception, #DB) and vector 3 (breakpoint exception, #BP). The following sections describe how these exceptions
are generated and typical exception handler operations.
17.3.1
Debug Exception (#DB)—Interrupt Vector 1
The debug-exception handler is usually a debugger program or part of a larger software system. The processor
generates a debug exception for any of several conditions. The debugger checks flags in the DR6 and DR7 registers
to determine which condition caused the exception and which other conditions might apply. Table 17-2 shows the
states of these flags following the generation of each kind of breakpoint condition.
Instruction-breakpoint and general-detect condition (see Section 17.3.1.3, “General-Detect Exception Condition”)
result in faults; other debug-exception conditions result in traps. The debug exception may report one or both at
one time. The following sections describe each class of debug exception.
17-6 Vol. 3B
DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
63
32
DR7
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
LEN R/W LEN R/W LEN R/W LEN R/W 0 0 G 0 0 1 G L G L G L G L G L
DR7
3
3
2
2
1
1
0
0
D
E E 3 3 2 2 1 1 0 0
63
32
DR6
31
16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Reserved (set to 1)
B B B 0 1 1 1 1 1 1 1 1 1 B B B B
DR6
T S D
3 2 1 0
63
0
DR5
63
0
DR4
63
0
DR3
Breakpoint 3 Linear Address
63
0
DR2
Breakpoint 2 Linear Address
63
0
DR1
Breakpoint 1 Linear Address
63
0
DR0
Breakpoint 0 Linear Address
Reserved
Figure 17-2. DR6/DR7 Layout on Processors Supporting Intel® 64 Architecture
See also: Chapter 6, “Interrupt 1—Debug Exception (#DB),” in the Intel® 64 and IA-32 Architectures Software
Developer’s Manual, Volume 3A.
Table 17-2. Debug Exception Conditions
Debug or Breakpoint Condition
DR6 Flags Tested
DR7 Flags Tested
Exception Class
Single-step trap
BS = 1
Instruction breakpoint, at addresses defined by DRn and
LENn
Bn = 1 and
(Gn or Ln = 1)
R/Wn = 0
Fault
Data write breakpoint, at addresses defined by DRn and
LENn
Bn = 1 and
(Gn or Ln = 1)
R/Wn = 1
Trap
Trap
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
Table 17-2. Debug Exception Conditions
Debug or Breakpoint Condition
DR6 Flags Tested
DR7 Flags Tested
Exception Class
I/O read or write breakpoint, at addresses defined by DRn
and LENn
Bn = 1 and
(Gn or Ln = 1)
R/Wn = 2
Trap
Data read or write (but not instruction fetches), at
addresses defined by DRn and LENn
Bn = 1 and
(Gn or Ln = 1)
R/Wn = 3
Trap
General detect fault, resulting from an attempt to modify
debug registers (usually in conjunction with in-circuit
emulation)
BD = 1
Fault
Task switch
BT = 1
Trap
17.3.1.1
Instruction-Breakpoint Exception Condition
The processor reports an instruction breakpoint when it attempts to execute an instruction at an address specified
in a breakpoint-address register (DR0 through DR3) that has been set up to detect instruction execution (R/W flag
is set to 0). Upon reporting the instruction breakpoint, the processor generates a fault-class, debug exception
(#DB) before it executes the target instruction for the breakpoint.
Instruction breakpoints are the highest priority debug exceptions. They are serviced before any other exceptions
detected during the decoding or execution of an instruction. However, if a code instruction breakpoint is placed on
an instruction located immediately after a POP SS/MOV SS instruction, the breakpoint may not be triggered. In
most situations, POP SS/MOV SS will inhibit such interrupts (see “MOV—Move” and “POP—Pop a Value from the
Stack” in Chapter 4 of the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 2B).
Because the debug exception for an instruction breakpoint is generated before the instruction is executed, if the
instruction breakpoint is not removed by the exception handler; the processor will detect the instruction breakpoint
again when the instruction is restarted and generate another debug exception. To prevent looping on an instruction
breakpoint, the Intel 64 and IA-32 architectures provide the RF flag (resume flag) in the EFLAGS register (see
Section 2.3, “System Flags and Fields in the EFLAGS Register,” in the Intel® 64 and IA-32 Architectures Software
Developer’s Manual, Volume 3A). When the RF flag is set, the processor ignores instruction breakpoints.
All Intel 64 and IA-32 processors manage the RF flag as follows. The RF Flag is cleared at the start of the instruction
after the check for code breakpoint, CS limit violation and FP exceptions. Task Switches and IRETD/IRETQ instructions transfer the RF image from the TSS/stack to the EFLAGS register.
When calling an event handler, Intel 64 and IA-32 processors establish the value of the RF flag in the EFLAGS image
pushed on the stack:
•
For any fault-class exception except a debug exception generated in response to an instruction breakpoint, the
value pushed for RF is 1.
•
For any interrupt arriving after any iteration of a repeated string instruction but the last iteration, the value
pushed for RF is 1.
•
For any trap-class exception generated by any iteration of a repeated string instruction but the last iteration,
the value pushed for RF is 1.
•
For other cases, the value pushed for RF is the value that was in EFLAG.RF at the time the event handler was
called. This includes:
— Debug exceptions generated in response to instruction breakpoints
— Hardware-generated interrupts arriving between instructions (including those arriving after the last
iteration of a repeated string instruction)
— Trap-class exceptions generated after an instruction completes (including those generated after the last
iteration of a repeated string instruction)
— Software-generated interrupts (RF is pushed as 0, since it was cleared at the start of the software interrupt)
As noted above, the processor does not set the RF flag prior to calling the debug exception handler for debug
exceptions resulting from instruction breakpoints. The debug exception handler can prevent recurrence of the
instruction breakpoint by setting the RF flag in the EFLAGS image on the stack. If the RF flag in the EFLAGS image
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
is set when the processor returns from the exception handler, it is copied into the RF flag in the EFLAGS register by
IRETD/IRETQ or a task switch that causes the return. The processor then ignores instruction breakpoints for the
duration of the next instruction. (Note that the POPF, POPFD, and IRET instructions do not transfer the RF image
into the EFLAGS register.) Setting the RF flag does not prevent other types of debug-exception conditions (such as,
I/O or data breakpoints) from being detected, nor does it prevent non-debug exceptions from being generated.
For the Pentium processor, when an instruction breakpoint coincides with another fault-type exception (such as a
page fault), the processor may generate one spurious debug exception after the second exception has been
handled, even though the debug exception handler set the RF flag in the EFLAGS image. To prevent a spurious
exception with Pentium processors, all fault-class exception handlers should set the RF flag in the EFLAGS image.
17.3.1.2
Data Memory and I/O Breakpoint Exception Conditions
Data memory and I/O breakpoints are reported when the processor attempts to access a memory or I/O address
specified in a breakpoint-address register (DR0 through DR3) that has been set up to detect data or I/O accesses
(R/W flag is set to 1, 2, or 3). The processor generates the exception after it executes the instruction that made the
access, so these breakpoint condition causes a trap-class exception to be generated.
Because data breakpoints are traps, an instruction that writes memory overwrites the original data before the
debug exception generated by a data breakpoint is generated. If a debugger needs to save the contents of a write
breakpoint location, it should save the original contents before setting the breakpoint. The handler can report the
saved value after the breakpoint is triggered. The address in the debug registers can be used to locate the new
value stored by the instruction that triggered the breakpoint.
If a data breakpoint is detected during an iteration of a string instruction executed with fast-string operation (see
Section 7.3.9.3 of Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 1), delivery of the
resulting debug exception may be delayed until completion of the corresponding group of iterations.
Intel486 and later processors ignore the GE and LE flags in DR7. In Intel386 processors, exact data breakpoint
matching does not occur unless it is enabled by setting the LE and/or the GE flags.
For repeated INS and OUTS instructions that generate an I/O-breakpoint debug exception, the processor generates the exception after the completion of the first iteration. Repeated INS and OUTS instructions generate a databreakpoint debug exception after the iteration in which the memory address breakpoint location is accessed.
17.3.1.3
General-Detect Exception Condition
When the GD flag in DR7 is set, the general-detect debug exception occurs when a program attempts to access any
of the debug registers (DR0 through DR7) at the same time they are being used by another application, such as an
emulator or debugger. This protection feature guarantees full control over the debug registers when required. The
debug exception handler can detect this condition by checking the state of the BD flag in the DR6 register. The
processor generates the exception before it executes the MOV instruction that accesses a debug register, which
causes a fault-class exception to be generated.
17.3.1.4
Single-Step Exception Condition
The processor generates a single-step debug exception if (while an instruction is being executed) it detects that the
TF flag in the EFLAGS register is set. The exception is a trap-class exception, because the exception is generated
after the instruction is executed. The processor will not generate this exception after the instruction that sets the
TF flag. For example, if the POPF instruction is used to set the TF flag, a single-step trap does not occur until after
the instruction that follows the POPF instruction.
The processor clears the TF flag before calling the exception handler. If the TF flag was set in a TSS at the time of
a task switch, the exception occurs after the first instruction is executed in the new task.
The TF flag normally is not cleared by privilege changes inside a task. The INT n and INTO instructions, however,
do clear this flag. Therefore, software debuggers that single-step code must recognize and emulate INT n or INTO
instructions rather than executing them directly. To maintain protection, the operating system should check the
CPL after any single-step trap to see if single stepping should continue at the current privilege level.
The interrupt priorities guarantee that, if an external interrupt occurs, single stepping stops. When both an
external interrupt and a single-step interrupt occur together, the single-step interrupt is processed first. This operVol. 3B 17-9
DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
ation clears the TF flag. After saving the return address or switching tasks, the external interrupt input is examined
before the first instruction of the single-step handler executes. If the external interrupt is still pending, then it is
serviced. The external interrupt handler does not run in single-step mode. To single step an interrupt handler,
single step an INT n instruction that calls the interrupt handler.
17.3.1.5
Task-Switch Exception Condition
The processor generates a debug exception after a task switch if the T flag of the new task's TSS is set. This exception is generated after program control has passed to the new task, and prior to the execution of the first instruction of that task. The exception handler can detect this condition by examining the BT flag of the DR6 register.
If entry 1 (#DB) in the IDT is a task gate, the T bit of the corresponding TSS should not be set. Failure to observe
this rule will put the processor in a loop.
17.3.2
Breakpoint Exception (#BP)—Interrupt Vector 3
The breakpoint exception (interrupt 3) is caused by execution of an INT 3 instruction. See Chapter 6, “Interrupt
3—Breakpoint Exception (#BP).” Debuggers use break exceptions in the same way that they use the breakpoint
registers; that is, as a mechanism for suspending program execution to examine registers and memory locations.
With earlier IA-32 processors, breakpoint exceptions are used extensively for setting instruction breakpoints.
With the Intel386 and later IA-32 processors, it is more convenient to set breakpoints with the breakpoint-address
registers (DR0 through DR3). However, the breakpoint exception still is useful for breakpointing debuggers,
because a breakpoint exception can call a separate exception handler. The breakpoint exception is also useful when
it is necessary to set more breakpoints than there are debug registers or when breakpoints are being placed in the
source code of a program under development.
17.3.3
Debug Exceptions, Breakpoint Exceptions, and Restricted Transactional Memory
(RTM)
Chapter 15, “Programming with Intel® Transactional Synchronization Extensions‚” of Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 1 describes Restricted Transactional Memory (RTM). This is an
instruction-set interface that allows software to identify transactional regions (or critical sections) using the
XBEGIN and XEND instructions.
Execution of an RTM transactional region begins with an XBEGIN instruction. If execution of the region successfully
reaches an XEND instruction, the processor ensures that all memory operations performed within the region
appear to have occurred instantaneously when viewed from other logical processors. Execution of an RTM transaction region does not succeed if the processor cannot commit the updates atomically. When this happens, the
processor rolls back the execution, a process referred to as a transactional abort. In this case, the processor
discards all updates performed in the region, restores architectural state to appear as if the execution had not
occurred, and resumes execution at a fallback instruction address that was specified with the XBEGIN instruction.
If debug exception (#DB) or breakpoint exception (#BP) occurs within an RTM transaction region, a transactional
abort occurs, the processor sets EAX[4], and no exception is delivered.
Software can enable advanced debugging of RTM transactional regions by setting DR7.RTM[bit 11] and
IA32_DEBUGCTL.RTM[bit 15]. If these bits are both set, the transactional abort caused by a #DB or #BP within an
RTM transaction region does not resume execution at the fallback instruction address specified with the XBEGIN
instruction that begin the region. Instead, execution is resumed at that XBEGIN instruction, and a #DB is delivered.
(A #DB is delivered even if the transactional abort was caused by a #BP.) Such a #DB will clear DR6.RTM[bit 16]
(all other debug exceptions set DR6[16]).
17.4
LAST BRANCH, INTERRUPT, AND EXCEPTION RECORDING OVERVIEW
P6 family processors introduced the ability to set breakpoints on taken branches, interrupts, and exceptions, and
to single-step from one branch to the next. This capability has been modified and extended in the Pentium 4, Intel
17-10 Vol. 3B
DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
Xeon, Pentium M, Intel® Core™ Solo, Intel® Core™ Duo, Intel® Core™2 Duo, Intel® Core™ i7 and Intel® Atom™
processors to allow logging of branch trace messages in a branch trace store (BTS) buffer in memory.
See the following sections for processor specific implementation of last branch, interrupt and exception recording:
— Section 17.5, “Last Branch, Interrupt, and Exception Recording (Intel® Core™ 2 Duo and Intel® Atom™
Processors)”
— Section 17.6, “Last Branch, Call Stack, Interrupt, and Exception Recording for Processors based on
Goldmont Microarchitecture”
— Section 17.7, “Last Branch, Interrupt, and Exception Recording for Processors based on Intel® Microarchitecture code name Nehalem”
— Section 17.8, “Last Branch, Interrupt, and Exception Recording for Processors based on Intel® Microarchitecture code name Sandy Bridge”
— Section 17.9, “Last Branch, Call Stack, Interrupt, and Exception Recording for Processors based on Haswell
Microarchitecture”
— Section 17.10, “Last Branch, Call Stack, Interrupt, and Exception Recording for Processors based on
Skylake Microarchitecture”
— Section 17.12, “Last Branch, Interrupt, and Exception Recording (Intel® Core™ Solo and Intel® Core™
Duo Processors)”
— Section 17.13, “Last Branch, Interrupt, and Exception Recording (Pentium M Processors)”
— Section 17.14, “Last Branch, Interrupt, and Exception Recording (P6 Family Processors)”
The following subsections of Section 17.4 describe common features of profiling branches. These features are
generally enabled using the IA32_DEBUGCTL MSR (older processor may have implemented a subset or modelspecific features, see definitions of MSR_DEBUGCTLA, MSR_DEBUGCTLB, MSR_DEBUGCTL).
17.4.1
IA32_DEBUGCTL MSR
The IA32_DEBUGCTL MSR provides bit field controls to enable debug trace interrupts, debug trace stores, trace
messages enable, single stepping on branches, last branch record recording, and to control freezing of LBR stack
or performance counters on a PMI request. IA32_DEBUGCTL MSR is located at register address 01D9H.
See Figure 17-3 for the MSR layout and the bullets below for a description of the flags:
•
LBR (last branch/interrupt/exception) flag (bit 0) — When set, the processor records a running trace of
the most recent branches, interrupts, and/or exceptions taken by the processor (prior to a debug exception
being generated) in the last branch record (LBR) stack. For more information, see the Section 17.5.1, “LBR
Stack” (Intel® Core™2 Duo and Intel® Atom™ Processor Family) and Section 17.7.1, “LBR Stack” (processors
based on Intel® Microarchitecture code name Nehalem).
•
BTF (single-step on branches) flag (bit 1) — When set, the processor treats the TF flag in the EFLAGS
register as a “single-step on branches” flag rather than a “single-step on instructions” flag. This mechanism
allows single-stepping the processor on taken branches. See Section 17.4.3, “Single-Stepping on Branches,”
for more information about the BTF flag.
•
TR (trace message enable) flag (bit 6) — When set, branch trace messages are enabled. When the
processor detects a taken branch, interrupt, or exception; it sends the branch record out on the system bus as
a branch trace message (BTM). See Section 17.4.4, “Branch Trace Messages,” for more information about the
TR flag.
•
BTS (branch trace store) flag (bit 7) — When set, the flag enables BTS facilities to log BTMs to a memoryresident BTS buffer that is part of the DS save area. See Section 17.4.9, “BTS and DS Save Area.”
•
BTINT (branch trace interrupt) flag (bit 8) — When set, the BTS facilities generate an interrupt when the
BTS buffer is full. When clear, BTMs are logged to the BTS buffer in a circular fashion. See Section 17.4.5, “Branch
Trace Store (BTS),” for a description of this mechanism.
Vol. 3B 17-11
DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
31
15 14
12 11 10 9 8 7 6 5 4 3 2 1 0
Reserved
RTM
FREEZE_WHILE_SMM_EN
FREEZE_PERFMON_ON_PMI
FREEZE_LBRS_ON_PMI
BTS_OFF_USR — BTS off in user code
BTS_OFF_OS — BTS off in OS
BTINT — Branch trace interrupt
BTS — Branch trace store
TR — Trace messages enable
Reserved
BTF — Single-step on branches
LBR — Last branch/interrupt/exception
Figure 17-3. IA32_DEBUGCTL MSR for Processors based
on Intel Core microarchitecture
•
BTS_OFF_OS (branch trace off in privileged code) flag (bit 9) — When set, BTS or BTM is skipped if CPL
is 0. See Section 17.11.2.
•
BTS_OFF_USR (branch trace off in user code) flag (bit 10) — When set, BTS or BTM is skipped if CPL is
greater than 0. See Section 17.11.2.
•
FREEZE_LBRS_ON_PMI flag (bit 11) — When set, the LBR stack is frozen on a hardware PMI request (e.g.
when a counter overflows and is configured to trigger PMI). See Section 17.4.7 for details.
•
FREEZE_PERFMON_ON_PMI flag (bit 12) — When set, the performance counters (IA32_PMCx and
IA32_FIXED_CTRx) are frozen on a PMI request. See Section 17.4.7 for details.
•
FREEZE_WHILE_SMM_EN (bit 14) — If this bit is set, upon the delivery of an SMI, the processor will clear all
the enable bits of IA32_PERF_GLOBAL_CTRL, save a copy of the content of IA32_DEBUGCTL and disable LBR,
BTF, TR, and BTS fields of IA32_DEBUGCTL before transferring control to the SMI handler. Subsequently, the
enable bits of IA32_PERF_GLOBAL_CTRL will be set to 1, the saved copy of IA32_DEBUGCTL prior to SMI
delivery will be restored, after the SMI handler issues RSM to complete its service. Note that system software
must check if the processor supports the IA32_DEBUGCTL.FREEZE_WHILE_SMM_EN control bit.
IA32_DEBUGCTL.FREEZE_WHILE_SMM_EN is supported if
IA32_PERF_CAPABILITIES.FREEZE_WHILE_SMM[Bit 12] is reporting 1. See Section 18.17 for details of
detecting the presence of IA32_PERF_CAPABILITIES MSR.
•
RTM (bit 15) — If this bit is set, advanced debugging of RTM transactional regions is enabled if DR7.RTM is
also set. See Section 17.3.3.
17.4.2
Monitoring Branches, Exceptions, and Interrupts
When the LBR flag (bit 0) in the IA32_DEBUGCTL MSR is set, the processor automatically begins recording branch
records for taken branches, interrupts, and exceptions (except for debug exceptions) in the LBR stack MSRs.
When the processor generates a debug exception (#DB), it automatically clears the LBR flag before executing the
exception handler. This action does not clear previously stored LBR stack MSRs.
A debugger can use the linear addresses in the LBR stack to re-set breakpoints in the breakpoint address registers
(DR0 through DR3). This allows a backward trace from the manifestation of a particular bug toward its source.
On some processors, if the LBR flag is cleared and TR flag in the IA32_DEBUGCTL MSR remains set, the processor
will continue to update LBR stack MSRs. This is because those processors use the entries in the LBR stack in the
process of generating BTM/BTS records. A #DB does not automatically clear the TR flag.
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
17.4.3
Single-Stepping on Branches
When software sets both the BTF flag (bit 1) in the IA32_DEBUGCTL MSR and the TF flag in the EFLAGS register,
the processor generates a single-step debug exception only after instructions that cause a branch.1 This mechanism allows a debugger to single-step on control transfers caused by branches. This “branch single stepping” helps
isolate a bug to a particular block of code before instruction single-stepping further narrows the search. The
processor clears the BTF flag when it generates a debug exception. The debugger must set the BTF flag before
resuming program execution to continue single-stepping on branches.
17.4.4
Branch Trace Messages
Setting the TR flag (bit 6) in the IA32_DEBUGCTL MSR enables branch trace messages (BTMs). Thereafter, when
the processor detects a branch, exception, or interrupt, it sends a branch record out on the system bus as a BTM.
A debugging device that is monitoring the system bus can read these messages and synchronize operations with
taken branch, interrupt, and exception events.
When interrupts or exceptions occur in conjunction with a taken branch, additional BTMs are sent out on the bus,
as described in Section 17.4.2, “Monitoring Branches, Exceptions, and Interrupts.”
For P6 processor family, Pentium M processor family, processors based on Intel Core microarchitecture, TR and LBR
bits can not be set at the same time due to hardware limitation. The content of LBR stack is undefined when TR is
set.
For processors with Intel NetBurst microarchitecture, Intel Atom processors, and Intel Core and related Intel Xeon
processors both starting with the Nehalem microarchitecture, the processor can collect branch records in the LBR
stack and at the same time send/store BTMs when both the TR and LBR flags are set in the IA32_DEBUGCTL MSR
(or the equivalent MSR_DEBUGCTLA, MSR_DEBUGCTLB).
The following exception applies:
•
BTM may not be observable on Intel Atom processor families that do not provide an externally visible system
bus (i.e., processors based on the Silvermont microarchitecture or later).
17.4.4.1
Branch Trace Message Visibility
Branch trace message (BTM) visibility is implementation specific and limited to systems with a front side bus
(FSB). BTMs may not be visible to newer system link interfaces or a system bus that deviates from a traditional
FSB.
17.4.5
Branch Trace Store (BTS)
A trace of taken branches, interrupts, and exceptions is useful for debugging code by providing a method of determining the decision path taken to reach a particular code location. The LBR flag (bit 0) of IA32_DEBUGCTL provides
a mechanism for capturing records of taken branches, interrupts, and exceptions and saving them in the last
branch record (LBR) stack MSRs, setting the TR flag for sending them out onto the system bus as BTMs. The branch
trace store (BTS) mechanism provides the additional capability of saving the branch records in a memory-resident
BTS buffer, which is part of the DS save area. The BTS buffer can be configured to be circular so that the most
recent branch records are always available or it can be configured to generate an interrupt when the buffer is
nearly full so that all the branch records can be saved. The BTINT flag (bit 8) can be used to enable the generation
of interrupt when the BTS buffer is full. See Section 17.4.9.2, “Setting Up the DS Save Area.” for additional details.
Setting this flag (BTS) alone can greatly reduce the performance of the processor. CPL-qualified branch trace
storing mechanism can help mitigate the performance impact of sending/logging branch trace messages.
1. Executions of CALL, IRET, and JMP that cause task switches never cause single-step debug exceptions (regardless of the value of the
BTF flag). A debugger desiring debug exceptions on switches to a task should set the T flag (debug trap flag) in the TSS of that task.
See Section 7.2.1, “Task-State Segment (TSS).”
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
17.4.6
CPL-Qualified Branch Trace Mechanism
CPL-qualified branch trace mechanism is available to a subset of Intel 64 and IA-32 processors that support the
branch trace storing mechanism. The processor supports the CPL-qualified branch trace mechanism if
CPUID.01H:ECX[bit 4] = 1.
The CPL-qualified branch trace mechanism is described in Section 17.4.9.4. System software can selectively specify
CPL qualification to not send/store Branch Trace Messages associated with a specified privilege level. Two bit fields,
BTS_OFF_USR (bit 10) and BTS_OFF_OS (bit 9), are provided in the debug control register to specify the CPL of
BTMs that will not be logged in the BTS buffer or sent on the bus.
17.4.7
Freezing LBR and Performance Counters on PMI
Many issues may generate a performance monitoring interrupt (PMI); a PMI service handler will need to determine
cause to handle the situation. Two capabilities that allow a PMI service routine to improve branch tracing and
performance monitoring are available for processors supporting architectural performance monitoring version 2 or
greater (i.e. CPUID.0AH:EAX[7:0] > 1). These capabilities provides the following interface in IA32_DEBUGCTL to
reduce runtime overhead of PMI servicing, profiler-contributed skew effects on analysis or counter metrics:
•
Freezing LBRs on PMI (bit 11)— Allows the PMI service routine to ensure the content in the LBR stack are
associated with the target workload and not polluted by the branch flows of handling the PMI. Depending on the
version ID enumerated by CPUID.0AH:EAX.ArchPerfMonVerID[bits 7:0], two flavors are supported:
— Legacy Freeze_LBR_on_PMI is supported for ArchPerfMonVerID <= 3 and ArchPerfMonVerID >1. If
IA32_DEBUGCTL.Freeze_LBR_On_PMI = 1, the LBR is frozen on the overflowed condition of the buffer
area, the processor clears the LBR bit (bit 0) in IA32_DEBUGCTL. Software must then re-enable
IA32_DEBUGCTL.LBR to resume recording branches. When using this feature, software should be careful
about writes to IA32_DEBUGCTL to avoid re-enabling LBRs by accident if they were just disabled.
— Streamlined Freeze_LBR_on_PMI is supported for ArchPerfMonVerID >= 4. If
IA32_DEBUGCTL.Freeze_LBR_On_PMI = 1, the processor behaves as follows:
•
•
sets IA32_PERF_GLOBAL_STATUS.LBR_Frz =1 to disable recording, but does not change the LBR bit
(bit 0) in IA32_DEBUGCTL. The LBRs are frozen on the overflowed condition of the buffer area.
Freezing PMCs on PMI (bit 12) — Allows the PMI service routine to ensure the content in the performance
counters are associated with the target workload and not polluted by the PMI and activities within the PMI
service routine. Depending on the version ID enumerated by CPUID.0AH:EAX.ArchPerfMonVerID[bits 7:0], two
flavors are supported:
— Legacy Freeze_Perfmon_on_PMI is supported for ArchPerfMonVerID <= 3 and ArchPerfMonVerID >1. If
IA32_DEBUGCTL.Freeze_Perfmon_On_PMI = 1, the performance counters are frozen on the counter
overflowed condition when the processor clears the IA32_PERF_GLOBAL_CTRL MSR (see Figure 18-3). The
PMCs affected include both general-purpose counters and fixed-function counters (see Section 18.4.1,
“Fixed-function Performance Counters”). Software must re-enable counts by writing 1s to the corresponding enable bits in IA32_PERF_GLOBAL_CTRL before leaving a PMI service routine to continue counter
operation.
— Streamlined Freeze_Perfmon_on_PMI is supported for ArchPerfMonVerID >= 4. The processor behaves as
follows:
•
sets IA32_PERF_GLOBAL_STATUS.CTR_Frz =1 to disable counting on a counter overflow condition, but
does not change the IA32_PERF_GLOBAL_CTRL MSR.
Freezing LBRs and PMCs on PMIs (both legacy and streamlined operation) occur when one of the following applies:
•
A performance counter had an overflow and was programmed to signal a PMI in case of an overflow.
— For the general-purpose counters; enabling PMI is done by setting bit 20 of the IA32_PERFEVTSELx
register.
— For the fixed-function counters; enabling PMI is done by setting the 3rd bit in the corresponding 4-bit
control field of the MSR_PERF_FIXED_CTR_CTRL register (see Figure 18-1) or IA32_FIXED_CTR_CTRL MSR
(see Figure 18-2).
•
The PEBS buffer is almost full and reaches the interrupt threshold.
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•
The BTS buffer is almost full and reaches the interrupt threshold.
Table 17-3 compares the interaction of the processor with the PMI handler using the legacy versus streamlined
Freeza_Perfmon_On_PMI interface.
Table 17-3. Legacy and Streamlined Operation with Freeze_Perfmon_On_PMI = 1, Counter Overflowed
Legacy Freeze_Perfmon_On_PMI
Streamlined Freeze_Perfmon_On_PMI
Comment
Processor freezes the counters on overflow
Processor freezes the counters on overflow
Unchanged
Processor clears IA32_PERF_GLOBAL_CTRL
Processor set
IA32_PERF_GLOBAL_STATUS.CTR_FTZ
Handler reads IA32_PERF_GLOBAL_STATUS
mask = RDMSR(0x38E)
(0x38E) to examine which counter(s) overflowed
Similar
Handler services the PMI
Handler services the PMI
Unchanged
Handler writes 1s to
IA32_PERF_GLOBAL_OVF_CTL (0x390)
Handler writes mask into
IA32_PERF_GLOBAL_OVF_RESET (0x390)
Processor clears IA32_PERF_GLOBAL_STATUS
Processor clears IA32_PERF_GLOBAL_STATUS Unchanged
Handler re-enables IA32_PERF_GLOBAL_CTRL
None
17.4.8
Reduced software overhead
LBR Stack
The last branch record stack and top-of-stack (TOS) pointer MSRs are supported across Intel 64 and IA-32
processor families. However, the number of MSRs in the LBR stack and the valid range of TOS pointer value can
vary between different processor families. Table 17-4 lists the LBR stack size and TOS pointer range for several
processor families according to the CPUID signatures of DisplayFamily_DisplayModel encoding (see CPUID instruction in Chapter 3 of Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 2A).
Table 17-4. LBR Stack Size and TOS Pointer Range
DisplayFamily_DisplayModel
Size of LBR Stack
Component of an LBR Entry
Range of TOS Pointer
06_5CH, 06_5FH
32
FROM_IP, TO_IP
0 to 31
1
06_4EH, 06_5EH, 06_8EH, 06_9EH
32
FROM_IP, TO_IP, LBR_INFO
0 to 31
06_3DH, 06_47H, 06_4FH, 06_56H
16
FROM_IP, TO_IP
0 to 15
06_3CH, 06_45H, 06_46H, 06_3FH
16
FROM_IP, TO_IP
0 to 15
06_2AH, 06_2DH, 06_3AH, 06_3EH
16
FROM_IP, TO_IP
0 to 15
06_1AH, 06_1EH, 06_1FH, 06_2EH, 06_25H,
06_2CH, 06_2FH
16
FROM_IP, TO_IP
0 to 15
06_17H, 06_1DH
4
FROM_IP, TO_IP
0 to 3
06_0FH
4
FROM_IP, TO_IP
0 to 3
06_37H, 06_4AH, 06_4CH, 06_4DH, 06_5AH,
06_5DH
8
FROM_IP, TO_IP
0 to 7
06_1CH, 06_26H, 06_27H, 06_35H, 06_36H
8
FROM_IP, TO_IP
0 to 7
NOTES:
1. See Section 17.10.
The last branch recording mechanism tracks not only branch instructions (like JMP, Jcc, LOOP and CALL instructions), but also other operations that cause a change in the instruction pointer (like external interrupts, traps and
faults). The branch recording mechanisms generally employs a set of MSRs, referred to as last branch record (LBR)
stack. The size and exact locations of the LBR stack are generally model-specific (see Chapter 35, “Model-Specific
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
Registers (MSRs)” of Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 3C for modelspecific MSR addresses).
•
Last Branch Record (LBR) Stack — The LBR consists of N pairs of MSRs (N is listed in the LBR stack size
column of Table 17-4) that store source and destination address of recent branches (see Figure 17-3):
— MSR_LASTBRANCH_0_FROM_IP (address is model specific) through the next consecutive (N-1) MSR
address store source addresses.
— MSR_LASTBRANCH_0_TO_IP (address is model specific ) through the next consecutive (N-1) MSR address
store destination addresses.
•
Last Branch Record Top-of-Stack (TOS) Pointer — The lowest significant M bits of the TOS Pointer MSR
(MSR_LASTBRANCH_TOS, address is model specific) contains an M-bit pointer to the MSR in the LBR stack that
contains the most recent branch, interrupt, or exception recorded. The valid range of the M-bit POS pointer is
given in Table 17-4.
17.4.8.1
LBR Stack and Intel® 64 Processors
LBR MSRs are 64-bits. In 64-bit mode, last branch records store the full address. Outside of 64-bit mode, the upper
32-bits of branch addresses will be stored as 0.
MSR_LASTBRANCH_0_FROM_IP through MSR_LASTBRANCH_(N-1)_FROM_IP
0
63
Source Address
MSR_LASTBRANCH_0_TO_IP through MSR_LASTBRANCH_(N-1)_TO_IP
0
63
Destination Address
Figure 17-4. 64-bit Address Layout of LBR MSR
Software should query an architectural MSR IA32_PERF_CAPABILITIES[5:0] about the format of the address that
is stored in the LBR stack. Four formats are defined by the following encoding:
— 000000B (32-bit record format) — Stores 32-bit offset in current CS of respective source/destination,
— 000001B (64-bit LIP record format) — Stores 64-bit linear address of respective source/destination,
— 000010B (64-bit EIP record format) — Stores 64-bit offset (effective address) of respective
source/destination.
— 000011B (64-bit EIP record format) and Flags — Stores 64-bit offset (effective address) of respective
source/destination. Misprediction info is reported in the upper bit of 'FROM' registers in the LBR stack. See
LBR stack details below for flag support and definition.
— 000100B (64-bit EIP record format), Flags and TSX — Stores 64-bit offset (effective address) of
respective source/destination. Misprediction and TSX info are reported in the upper bits of ‘FROM’ registers
in the LBR stack.
— 000101B (64-bit EIP record format), Flags, TSX, LBR_INFO — Stores 64-bit offset (effective
address) of respective source/destination. Misprediction, TSX, and elapsed cycles since the last LBR update
are reported in the LBR_INFO MSR stack.
— 000110B (64-bit EIP record format), Flags, Cycles — Stores 64-bit linear address (CS.Base +
effective address) of respective source/destination. Misprediction info is reported in the upper bits of
'FROM' registers in the LBR stack. Elapsed cycles since the last LBR update are reported in the upper 16 bits
of the 'TO' registers in the LBR stack (see Section 17.6).
Processor’s support for the architectural MSR IA32_PERF_CAPABILITIES is provided by
CPUID.01H:ECX[PERF_CAPAB_MSR] (bit 15).
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17.4.8.2
LBR Stack and IA-32 Processors
The LBR MSRs in IA-32 processors introduced prior to Intel 64 architecture store the 32-bit “To Linear Address” and
“From Linear Address“ using the high and low half of each 64-bit MSR.
17.4.8.3
Last Exception Records and Intel 64 Architecture
Intel 64 and IA-32 processors also provide MSRs that store the branch record for the last branch taken prior to an
exception or an interrupt. The location of the last exception record (LER) MSRs are model specific. The MSRs that
store last exception records are 64-bits. If IA-32e mode is disabled, only the lower 32-bits of the address is
recorded. If IA-32e mode is enabled, the processor writes 64-bit values into the MSR. In 64-bit mode, last exception records store 64-bit addresses; in compatibility mode, the upper 32-bits of last exception records are cleared.
17.4.9
BTS and DS Save Area
The Debug store (DS) feature flag (bit 21), returned by CPUID.1:EDX[21] indicates that the processor provides
the debug store (DS) mechanism. The DS mechanism allows:
•
•
BTMs to be stored in a memory-resident BTS buffer. See Section 17.4.5, “Branch Trace Store (BTS).”
Processor event-based sampling (PEBS) also uses the DS save area provided by debug store mechanism. The
capability of PEBS varies across different microarchitectures. See Section 18.4.4, “Processor Event Based
Sampling (PEBS),” and the relevant PEBS sub-sections across the core PMU sections in Chapter 18, “Performance Monitoring.”.
When CPUID.1:EDX[21] is set:
•
The BTS_UNAVAILABLE and PEBS_UNAVAILABLE flags in the IA32_MISC_ENABLE MSR indicate (when clear)
the availability of the BTS and PEBS facilities, including the ability to set the BTS and BTINT bits in the
appropriate DEBUGCTL MSR.
•
The IA32_DS_AREA MSR exists and points to the DS save area.
The debug store (DS) save area is a software-designated area of memory that is used to collect the following two
types of information:
•
Branch records — When the BTS flag in the IA32_DEBUGCTL MSR is set, a branch record is stored in the BTS
buffer in the DS save area whenever a taken branch, interrupt, or exception is detected.
•
PEBS records — When a performance counter is configured for PEBS, a PEBS record is stored in the PEBS
buffer in the DS save area after the counter overflow occurs. This record contains the architectural state of the
processor (state of the 8 general purpose registers, EIP register, and EFLAGS register) at the next occurrence
of the PEBS event that caused the counter to overflow. When the state information has been logged, the
counter is automatically reset to a specified value, and event counting begins again. The content layout of a
PEBS record varies across different implementations that support PEBS. See Section 18.4.4.2 for details of
enumerating PEBS record format.
NOTES
Prior to processors based on the Goldmont microarchitecture, PEBS facility only supports a subset
of implementation-specific precise events. See Section 18.7.1 for a PEBS enhancement that can
generate records for both precise and non-precise events.
The DS save area and recording mechanism are disabled on transition to system-management
mode (SMM). Similarly, the recording mechanism is disabled on the generation of a machine-check
exception and is cleared on processor RESET and INIT. DS recording is available in real-address
mode.
The BTS and PEBS facilities may not be available on all processors. The availability of these facilities
is indicated by the BTS_UNAVAILABLE and PEBS_UNAVAILABLE flags, respectively, in the
IA32_MISC_ENABLE MSR (see Chapter 35).
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
The DS save area is divided into three parts (see Figure 17-5): buffer management area, branch trace store (BTS)
buffer, and PEBS buffer. The buffer management area is used to define the location and size of the BTS and PEBS
buffers. The processor then uses the buffer management area to keep track of the branch and/or PEBS records in
their respective buffers and to record the performance counter reset value. The linear address of the first byte of
the DS buffer management area is specified with the IA32_DS_AREA MSR.
The fields in the buffer management area are as follows:
•
BTS buffer base — Linear address of the first byte of the BTS buffer. This address should point to a natural
doubleword boundary.
•
BTS index — Linear address of the first byte of the next BTS record to be written to. Initially, this address
should be the same as the address in the BTS buffer base field.
•
BTS absolute maximum — Linear address of the next byte past the end of the BTS buffer. This address should
be a multiple of the BTS record size (12 bytes) plus 1.
•
BTS interrupt threshold — Linear address of the BTS record on which an interrupt is to be generated. This
address must point to an offset from the BTS buffer base that is a multiple of the BTS record size. Also, it must
be several records short of the BTS absolute maximum address to allow a pending interrupt to be handled prior
to processor writing the BTS absolute maximum record.
•
PEBS buffer base — Linear address of the first byte of the PEBS buffer. This address should point to a natural
doubleword boundary.
•
PEBS index — Linear address of the first byte of the next PEBS record to be written to. Initially, this address
should be the same as the address in the PEBS buffer base field.
•
PEBS absolute maximum — Linear address of the next byte past the end of the PEBS buffer. This address
should be a multiple of the PEBS record size (40 bytes) plus 1.
•
PEBS interrupt threshold — Linear address of the PEBS record on which an interrupt is to be generated. This
address must point to an offset from the PEBS buffer base that is a multiple of the PEBS record size. Also, it
must be several records short of the PEBS absolute maximum address to allow a pending interrupt to be
handled prior to processor writing the PEBS absolute maximum record.
•
PEBS counter reset value — A 40-bit value that the counter is to be reset to after state information has
collected following counter overflow. This value allows state information to be collected after a preset number
of events have been counted.
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
IA32_DS_AREA MSR
DS Buffer Management Area
BTS Buffer Base
0H
BTS Index
4H
BTS Buffer
Branch Record 0
BTS Absolute
Maximum
BTS Interrupt
Threshold
8H
Branch Record 1
CH
PEBS Buffer Base 10H
PEBS Index
PEBS Absolute
Maximum
PEBS Interrupt
Threshold
PEBS
Counter Reset
Reserved
14H
18H
Branch Record n
1CH
20H
24H
PEBS Buffer
30H
PEBS Record 0
PEBS Record 1
PEBS Record n
Figure 17-5. DS Save Area
Figures 17-6 shows the structure of a 12-byte branch record in the BTS buffer. The fields in each record are as
follows:
•
Last branch from — Linear address of the instruction from which the branch, interrupt, or exception was
taken.
•
Last branch to — Linear address of the branch target or the first instruction in the interrupt or exception
service routine.
•
Branch predicted — Bit 4 of field indicates whether the branch that was taken was predicted (set) or not
predicted (clear).
31
4
0
Last Branch From
0H
Last Branch To
4H
8H
Branch Predicted
Figure 17-6. 32-bit Branch Trace Record Format
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Figure 17-7 shows the structure of the 40-byte PEBS records. Nominally the register values are those at the beginning of the instruction that caused the event. However, there are cases where the registers may be logged in a
partially modified state. The linear IP field shows the value in the EIP register translated from an offset into the
current code segment to a linear address.
31
0
EFLAGS
0H
Linear IP
4H
EAX
8H
EBX
CH
ECX
10H
EDX
14H
ESI
18H
EDI
1CH
EBP
20H
ESP
24H
Figure 17-7. PEBS Record Format
17.4.9.1
64 Bit Format of the DS Save Area
When DTES64 = 1 (CPUID.1.ECX[2] = 1), the structure of the DS save area is shown in Figure 17-8.
When DTES64 = 0 (CPUID.1.ECX[2] = 0) and IA-32e mode is active, the structure of the DS save area is shown in
Figure 17-8. If IA-32e mode is not active the structure of the DS save area is as shown in Figure 17-6.
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IA32_DS_AREA MSR
DS Buffer Management Area
BTS Buffer Base
0H
BTS Index
8H
BTS Buffer
Branch Record 0
BTS Absolute
Maximum
BTS Interrupt
Threshold
10H
Branch Record 1
18H
PEBS Buffer Base 20H
PEBS Index
PEBS Absolute
Maximum
PEBS Interrupt
Threshold
PEBS
Counter Reset
Reserved
28H
30H
Branch Record n
38H
40H
48H
PEBS Buffer
50H
PEBS Record 0
PEBS Record 1
PEBS Record n
Figure 17-8. IA-32e Mode DS Save Area
The IA32_DS_AREA MSR holds the 64-bit linear address of the first byte of the DS buffer management area. The
structure of a branch trace record is similar to that shown in Figure 17-6, but each field is 8 bytes in length. This
makes each BTS record 24 bytes (see Figure 17-9). The structure of a PEBS record is similar to that shown in
Figure 17-7, but each field is 8 bytes in length and architectural states include register R8 through R15. This makes
the size of a PEBS record in 64-bit mode 144 bytes (see Figure 17-10).
63
4
0
Last Branch From
0H
Last Branch To
8H
10H
Branch Predicted
Figure 17-9. 64-bit Branch Trace Record Format
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63
0
RFLAGS
0H
RIP
8H
RAX
10H
RBX
18H
RCX
20H
RDX
28H
RSI
30H
RDI
38H
RBP
40H
RSP
48H
R8
50H
...
...
R15
88H
Figure 17-10. 64-bit PEBS Record Format
Fields in the buffer management area of a DS save area are described in Section 17.4.9.
The format of a branch trace record and a PEBS record are the same as the 64-bit record formats shown in Figures
17-9 and Figures 17-10, with the exception that the branch predicted bit is not supported by Intel Core microarchitecture or Intel Atom microarchitecture. The 64-bit record formats for BTS and PEBS apply to DS save area for all
operating modes.
The procedures used to program IA32_DEBUGCTL MSR to set up a BTS buffer or a CPL-qualified BTS are described
in Section 17.4.9.3 and Section 17.4.9.4.
Required elements for writing a DS interrupt service routine are largely the same on processors that support using
DS Save area for BTS or PEBS records. However, on processors based on Intel NetBurst® microarchitecture, reenabling counting requires writing to CCCRs. But a DS interrupt service routine on processors supporting architectural performance monitoring should:
•
•
Re-enable the enable bits in IA32_PERF_GLOBAL_CTRL MSR if it is servicing an overflow PMI due to PEBS.
Clear overflow indications by writing to IA32_PERF_GLOBAL_OVF_CTRL when a counting configuration is
changed. This includes bit 62 (ClrOvfBuffer) and the overflow indication of counters used in either PEBS or
general-purpose counting (specifically: bits 0 or 1; see Figures 18-3).
17.4.9.2
Setting Up the DS Save Area
To save branch records with the BTS buffer, the DS save area must first be set up in memory as described in the
following procedure (See Section 18.4.4.1, “Setting up the PEBS Buffer,” for instructions for setting up a PEBS
buffer, respectively, in the DS save area):
1. Create the DS buffer management information area in memory (see Section 17.4.9, “BTS and DS Save Area,”
and Section 17.4.9.1, “64 Bit Format of the DS Save Area”). Also see the additional notes in this section.
2. Write the base linear address of the DS buffer management area into the IA32_DS_AREA MSR.
3. Set up the performance counter entry in the xAPIC LVT for fixed delivery and edge sensitive. See Section
10.5.1, “Local Vector Table.”
4. Establish an interrupt handler in the IDT for the vector associated with the performance counter entry in the
xAPIC LVT.
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5. Write an interrupt service routine to handle the interrupt. See Section 17.4.9.5, “Writing the DS Interrupt
Service Routine.”
The following restrictions should be applied to the DS save area.
•
The three DS save area sections should be allocated from a non-paged pool, and marked accessed and dirty. It
is the responsibility of the operating system to keep the pages that contain the buffer present and to mark
them accessed and dirty. The implication is that the operating system cannot do “lazy” page-table entry
propagation for these pages.
•
The DS save area can be larger than a page, but the pages must be mapped to contiguous linear addresses.
The buffer may share a page, so it need not be aligned on a 4-KByte boundary. For performance reasons, the
base of the buffer must be aligned on a doubleword boundary and should be aligned on a cache line boundary.
•
It is recommended that the buffer size for the BTS buffer and the PEBS buffer be an integer multiple of the
corresponding record sizes.
•
The precise event records buffer should be large enough to hold the number of precise event records that can
occur while waiting for the interrupt to be serviced.
•
The DS save area should be in kernel space. It must not be on the same page as code, to avoid triggering selfmodifying code actions.
•
There are no memory type restrictions on the buffers, although it is recommended that the buffers be
designated as WB memory type for performance considerations.
•
Either the system must be prevented from entering A20M mode while DS save area is active, or bit 20 of all
addresses within buffer bounds must be 0.
•
Pages that contain buffers must be mapped to the same physical addresses for all processes, such that any
change to control register CR3 will not change the DS addresses.
•
The DS save area is expected to used only on systems with an enabled APIC. The LVT Performance Counter
entry in the APCI must be initialized to use an interrupt gate instead of the trap gate.
17.4.9.3
Setting Up the BTS Buffer
Three flags in the MSR_DEBUGCTLA MSR (see Table 17-5), IA32_DEBUGCTL (see Figure 17-3), or
MSR_DEBUGCTLB (see Figure 17-16) control the generation of branch records and storing of them in the BTS
buffer; these are TR, BTS, and BTINT. The TR flag enables the generation of BTMs. The BTS flag determines
whether the BTMs are sent out on the system bus (clear) or stored in the BTS buffer (set). BTMs cannot be simultaneously sent to the system bus and logged in the BTS buffer. The BTINT flag enables the generation of an interrupt when the BTS buffer is full. When this flag is clear, the BTS buffer is a circular buffer.
Table 17-5. IA32_DEBUGCTL Flag Encodings
TR
BTS
BTINT
Description
0
X
X
Branch trace messages (BTMs) off
1
0
X
Generate BTMs
1
1
0
Store BTMs in the BTS buffer, used here as a circular buffer
1
1
1
Store BTMs in the BTS buffer, and generate an interrupt when the buffer is nearly full
The following procedure describes how to set up a DS Save area to collect branch records in the BTS buffer:
1. Place values in the BTS buffer base, BTS index, BTS absolute maximum, and BTS interrupt threshold fields of
the DS buffer management area to set up the BTS buffer in memory.
2. Set the TR and BTS flags in the IA32_DEBUGCTL for Intel Core Solo and Intel Core Duo processors or later
processors (or MSR_DEBUGCTLA MSR for processors based on Intel NetBurst Microarchitecture; or
MSR_DEBUGCTLB for Pentium M processors).
3. Clear the BTINT flag in the corresponding IA32_DEBUGCTL (or MSR_DEBUGCTLA MSR; or MSR_DEBUGCTLB)
if a circular BTS buffer is desired.
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
NOTES
If the buffer size is set to less than the minimum allowable value (i.e. BTS absolute maximum < 1
+ size of BTS record), the results of BTS is undefined.
In order to prevent generating an interrupt, when working with circular BTS buffer, SW need to set
BTS interrupt threshold to a value greater than BTS absolute maximum (fields of the DS buffer
management area). It's not enough to clear the BTINT flag itself only.
17.4.9.4
Setting Up CPL-Qualified BTS
If the processor supports CPL-qualified last branch recording mechanism, the generation of branch records and
storing of them in the BTS buffer are determined by: TR, BTS, BTS_OFF_OS, BTS_OFF_USR, and BTINT. The
encoding of these five bits are shown in Table 17-6.
Table 17-6. CPL-Qualified Branch Trace Store Encodings
TR
BTS
BTS_OFF_OS
BTS_OFF_USR
BTINT
Description
0
X
X
X
X
Branch trace messages (BTMs) off
1
0
X
X
X
Generates BTMs but do not store BTMs
1
1
0
0
0
Store all BTMs in the BTS buffer, used here as a circular buffer
1
1
1
0
0
Store BTMs with CPL > 0 in the BTS buffer
1
1
0
1
0
Store BTMs with CPL = 0 in the BTS buffer
1
1
1
1
X
Generate BTMs but do not store BTMs
1
1
0
0
1
Store all BTMs in the BTS buffer; generate an interrupt when the
buffer is nearly full
1
1
1
0
1
Store BTMs with CPL > 0 in the BTS buffer; generate an interrupt
when the buffer is nearly full
1
1
0
1
1
Store BTMs with CPL = 0 in the BTS buffer; generate an interrupt
when the buffer is nearly full
17.4.9.5
Writing the DS Interrupt Service Routine
The BTS, non-precise event-based sampling, and PEBS facilities share the same interrupt vector and interrupt
service routine (called the debug store interrupt service routine or DS ISR). To handle BTS, non-precise eventbased sampling, and PEBS interrupts: separate handler routines must be included in the DS ISR. Use the following
guidelines when writing a DS ISR to handle BTS, non-precise event-based sampling, and/or PEBS interrupts.
•
The DS interrupt service routine (ISR) must be part of a kernel driver and operate at a current privilege level of
0 to secure the buffer storage area.
•
Because the BTS, non-precise event-based sampling, and PEBS facilities share the same interrupt vector, the
DS ISR must check for all the possible causes of interrupts from these facilities and pass control on to the
appropriate handler.
BTS and PEBS buffer overflow would be the sources of the interrupt if the buffer index matches/exceeds the
interrupt threshold specified. Detection of non-precise event-based sampling as the source of the interrupt is
accomplished by checking for counter overflow.
•
•
There must be separate save areas, buffers, and state for each processor in an MP system.
•
The processor will not disable the DS save area when the buffer is full and the circular mode has not been
selected. The current DS setting must be retained and restored by the ISR on exit.
Upon entering the ISR, branch trace messages and PEBS should be disabled to prevent race conditions during
access to the DS save area. This is done by clearing TR flag in the IA32_DEBUGCTL (or MSR_DEBUGCTLA MSR)
and by clearing the precise event enable flag in the MSR_PEBS_ENABLE MSR. These settings should be
restored to their original values when exiting the ISR.
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
•
After reading the data in the appropriate buffer, up to but not including the current index into the buffer, the ISR
must reset the buffer index to the beginning of the buffer. Otherwise, everything up to the index will look like
new entries upon the next invocation of the ISR.
•
•
The ISR must clear the mask bit in the performance counter LVT entry.
•
The Pentium 4 Processor and Intel Xeon Processor mask PMIs upon receiving an interrupt. Clear this condition
before leaving the interrupt handler.
The ISR must re-enable the counters to count via IA32_PERF_GLOBAL_CTRL/IA32_PERF_GLOBAL_OVF_CTRL
if it is servicing an overflow PMI due to PEBS (or via CCCR's ENABLE bit on processor based on Intel NetBurst
microarchitecture).
17.5
LAST BRANCH, INTERRUPT, AND EXCEPTION RECORDING (INTEL® CORE™ 2
DUO AND INTEL® ATOM™ PROCESSORS)
The Intel Core 2 Duo processor family and Intel Xeon processors based on Intel Core microarchitecture or
enhanced Intel Core microarchitecture provide last branch interrupt and exception recording. The facilities
described in this section also apply to 45 nm and 32 nm Intel Atom processors. These capabilities are similar to
those found in Pentium 4 processors, including support for the following facilities:
•
Debug Trace and Branch Recording Control — The IA32_DEBUGCTL MSR provide bit fields for software to
configure mechanisms related to debug trace, branch recording, branch trace store, and performance counter
operations. See Section 17.4.1 for a description of the flags. See Figure 17-3 for the MSR layout.
•
Last branch record (LBR) stack — There are a collection of MSR pairs that store the source and destination
addresses related to recently executed branches. See Section 17.5.1.
•
Monitoring and single-stepping of branches, exceptions, and interrupts
— See Section 17.4.2 and Section 17.4.3. In addition, the ability to freeze the LBR stack on a PMI request is
available.
— 45 nm and 32 nm Intel Atom processors clear the TR flag when the FREEZE_LBRS_ON_PMI flag is set.
•
•
•
•
•
Branch trace messages — See Section 17.4.4.
•
FREEZE_WHILE_SMM_EN (bit 14) — FREEZE_WHILE_SMM_EN is supported if
IA32_PERF_CAPABILITIES.FREEZE_WHILE_SMM[Bit 12] is reporting 1. See Section 17.4.1.
Last exception records — See Section 17.11.3.
Branch trace store and CPL-qualified BTS — See Section 17.4.5.
FREEZE_LBRS_ON_PMI flag (bit 11) — see Section 17.4.7 for legacy Freeze_LBRs_On_PMI operation.
FREEZE_PERFMON_ON_PMI flag (bit 12) — see Section 17.4.7 for legacy Freeze_Perfmon_On_PMI
operation.
17.5.1
LBR Stack
The last branch record stack and top-of-stack (TOS) pointer MSRs are supported across Intel Core 2, Intel Atom
processor families, and Intel processors based on Intel NetBurst microarchitecture.
Four pairs of MSRs are supported in the LBR stack for Intel Core 2 processors families and Intel processors based
on Intel NetBurst microarchitecture:
•
Last Branch Record (LBR) Stack
— MSR_LASTBRANCH_0_FROM_IP (address 40H) through MSR_LASTBRANCH_3_FROM_IP (address 43H)
store source addresses
— MSR_LASTBRANCH_0_TO_IP (address 60H) through MSR_LASTBRANCH_3_TO_IP (address 63H) store
destination addresses
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
•
Last Branch Record Top-of-Stack (TOS) Pointer — The lowest significant 2 bits of the TOS Pointer MSR
(MSR_LASTBRANCH_TOS, address 1C9H) contains a pointer to the MSR in the LBR stack that contains the most
recent branch, interrupt, or exception recorded.
Eight pairs of MSRs are supported in the LBR stack for 45 nm and 32 nm Intel Atom processors:
•
Last Branch Record (LBR) Stack
— MSR_LASTBRANCH_0_FROM_IP (address 40H) through MSR_LASTBRANCH_7_FROM_IP (address 47H)
store source addresses
— MSR_LASTBRANCH_0_TO_IP (address 60H) through MSR_LASTBRANCH_7_TO_IP (address 67H) store
destination addresses
•
Last Branch Record Top-of-Stack (TOS) Pointer — The lowest significant 3 bits of the TOS Pointer MSR
(MSR_LASTBRANCH_TOS, address 1C9H) contains a pointer to the MSR in the LBR stack that contains the most
recent branch, interrupt, or exception recorded.
The address format written in the FROM_IP/TO_IP MSRS may differ between processors. Software should query
IA32_PERF_CAPABILITIES[5:0] and consult Section 17.4.8.1. The behavior of the MSR_LER_TO_LIP and the
MSR_LER_FROM_LIP MSRs corresponds to that of the LastExceptionToIP and LastExceptionFromIP MSRs found in
P6 family processors.
17.5.2
LBR Stack in Intel Atom Processors based on the Silvermont Microarchitecture
The last branch record stack and top-of-stack (TOS) pointer MSRs are supported in Intel Atom processors based on
the Silvermont and Airmont microarchitectures. Eight pairs of MSRs are supported in the LBR stack.
LBR filtering is supported. Filtering of LBRs based on a combination of CPL and branch type conditions is supported.
When LBR filtering is enabled, the LBR stack only captures the subset of branches that are specified by
MSR_LBR_SELECT. The layout of MSR_LBR_SELECT is described in Table 17-11.
17.6
LAST BRANCH, CALL STACK, INTERRUPT, AND EXCEPTION RECORDING
FOR PROCESSORS BASED ON GOLDMONT MICROARCHITECTURE
Next generation Intel Atom processors are based on the Goldmont microarchitecture. Processors based on the
Goldmont microarchitecture extend the capabilities described in Section 17.5.2 with the following enhancements:
•
•
Supports new LBR format encoding 00110b in IA32_PERF_CAPABILITIES[5:0].
•
LBR call stack filtering supported. The layout of MSR_LBR_SELECT is described in Table 17-13.
•
Elapsed cycle information is added to MSR_LASTBRANCH_x_TO_IP. Format is shown in Table 17-7.
•
Misprediction info is reported in the upper bits of MSR_LASTBRANCH_x_FROM_IP. MISPRED bit format is
shown in Table 17-8.
•
Streamlined Freeze_LBRs_On_PMI operation; see Section 17.10.2.
•
LBR MSRs are cleared when software requests C6 or deeper sleep-state; see Section 17.10.3.
Size of LBR stack increased to 32. Each entry includes MSR_LASTBRANCH_x_FROM_IP (address 0x680..0x69f)
and MSR_LASTBRANCH_x_TO_IP (address 0x6c0..0x6df).
Table 17-7. MSR_LASTBRANCH_x_TO_IP for the Goldmont Microarchitecture
Bit Field
Bit Offset
Access
Description
Data
47:0
R/O
This is the “branch to“ address. See Section 17.4.8.1 for address format.
Cycle Count
(Saturating)
63:48
R/0
Elapsed core clocks since last update to the LBR stack.
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
17.7
LAST BRANCH, INTERRUPT, AND EXCEPTION RECORDING FOR
PROCESSORS BASED ON INTEL® MICROARCHITECTURE CODE NAME
NEHALEM
The processors based on Intel® microarchitecture code name Nehalem and Intel® microarchitecture code name
Westmere support last branch interrupt and exception recording. These capabilities are similar to those found in
Intel Core 2 processors and adds additional capabilities:
•
Debug Trace and Branch Recording Control — The IA32_DEBUGCTL MSR provides bit fields for software to
configure mechanisms related to debug trace, branch recording, branch trace store, and performance counter
operations. See Section 17.4.1 for a description of the flags. See Figure 17-11 for the MSR layout.
•
Last branch record (LBR) stack — There are 16 MSR pairs that store the source and destination addresses
related to recently executed branches. See Section 17.7.1.
•
Monitoring and single-stepping of branches, exceptions, and interrupts — See Section 17.4.2 and
Section 17.4.3. In addition, the ability to freeze the LBR stack on a PMI request is available.
•
Branch trace messages — The IA32_DEBUGCTL MSR provides bit fields for software to enable each logical
processor to generate branch trace messages. See Section 17.4.4. However, not all BTM messages are
observable using the Intel® QPI link.
•
•
•
•
Last exception records — See Section 17.11.3.
•
UNCORE_PMI_EN (bit 13) — When set. this logical processor is enabled to receive an counter overflow
interrupt form the uncore.
•
FREEZE_WHILE_SMM_EN (bit 14) — FREEZE_WHILE_SMM_EN is supported if
IA32_PERF_CAPABILITIES.FREEZE_WHILE_SMM[Bit 12] is reporting 1. See Section 17.4.1.
Branch trace store and CPL-qualified BTS — See Section 17.4.6 and Section 17.4.5.
FREEZE_LBRS_ON_PMI flag (bit 11) — see Section 17.4.7 for legacy Freeze_LBRs_On_PMI operation.
FREEZE_PERFMON_ON_PMI flag (bit 12) — see Section 17.4.7 for legacy Freeze_Perfmon_On_PMI
operation.
Processors based on Intel microarchitecture code name Nehalem provide additional capabilities:
•
Independent control of uncore PMI — The IA32_DEBUGCTL MSR provides a bit field (see Figure 17-11) for
software to enable each logical processor to receive an uncore counter overflow interrupt.
•
LBR filtering — Processors based on Intel microarchitecture code name Nehalem support filtering of LBR
based on combination of CPL and branch type conditions. When LBR filtering is enabled, the LBR stack only
captures the subset of branches that are specified by MSR_LBR_SELECT.
31
14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
Reserved
FREEZE_WHILE_SMM_EN
UNCORE_PMI_EN
FREEZE_PERFMON_ON_PMI
FREEZE_LBRS_ON_PMI
BTS_OFF_USR — BTS off in user code
BTS_OFF_OS — BTS off in OS
BTINT — Branch trace interrupt
BTS — Branch trace store
TR — Trace messages enable
Reserved
BTF — Single-step on branches
LBR — Last branch/interrupt/exception
Figure 17-11. IA32_DEBUGCTL MSR for Processors based
on Intel microarchitecture code name Nehalem
Vol. 3B 17-27
DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
17.7.1
LBR Stack
Processors based on Intel microarchitecture code name Nehalem provide 16 pairs of MSR to record last branch
record information. The layout of each MSR pair is shown in Table 17-8 and Table 17-9.
Table 17-8. MSR_LASTBRANCH_x_FROM_IP
Bit Field
Bit Offset
Access
Description
Data
47:0
R/O
This is the “branch from“ address. See Section 17.4.8.1 for address format.
SIGN_EXt
62:48
R/0
Signed extension of bit 47 of this register.
MISPRED
63
R/O
When set, indicates either the target of the branch was mispredicted and/or the
direction (taken/non-taken) was mispredicted; otherwise, the target branch was
predicted.
Table 17-9. MSR_LASTBRANCH_x_TO_IP
Bit Field
Bit Offset
Access
Description
Data
47:0
R/O
This is the “branch to“ address. See Section 17.4.8.1 for address format
SIGN_EXt
63:48
R/0
Signed extension of bit 47 of this register.
Processors based on Intel microarchitecture code name Nehalem have an LBR MSR Stack as shown in Table 17-10.
Table 17-10. LBR Stack Size and TOS Pointer Range
DisplayFamily_DisplayModel
Size of LBR Stack
Range of TOS Pointer
06_1AH
16
0 to 15
17.7.2
Filtering of Last Branch Records
MSR_LBR_SELECT is cleared to zero at RESET, and LBR filtering is disabled, i.e. all branches will be captured.
MSR_LBR_SELECT provides bit fields to specify the conditions of subsets of branches that will not be captured in
the LBR. The layout of MSR_LBR_SELECT is shown in Table 17-11.
Table 17-11. MSR_LBR_SELECT for Intel microarchitecture code name Nehalem
Bit Field
Bit Offset
Access
Description
CPL_EQ_0
0
R/W
When set, do not capture branches occurring in ring 0
CPL_NEQ_0
1
R/W
When set, do not capture branches occurring in ring >0
JCC
2
R/W
When set, do not capture conditional branches
NEAR_REL_CALL
3
R/W
When set, do not capture near relative calls
NEAR_IND_CALL
4
R/W
When set, do not capture near indirect calls
NEAR_RET
5
R/W
When set, do not capture near returns
NEAR_IND_JMP
6
R/W
When set, do not capture near indirect jumps
NEAR_REL_JMP
7
R/W
When set, do not capture near relative jumps
FAR_BRANCH
8
R/W
When set, do not capture far branches
Reserved
63:9
17-28 Vol. 3B
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
17.8
LAST BRANCH, INTERRUPT, AND EXCEPTION RECORDING FOR
PROCESSORS BASED ON INTEL® MICROARCHITECTURE CODE NAME
SANDY BRIDGE
Generally, all of the last branch record, interrupt and exception recording facility described in Section 17.7, “Last
Branch, Interrupt, and Exception Recording for Processors based on Intel® Microarchitecture code name
Nehalem”, apply to processors based on Intel microarchitecture code name Sandy Bridge. For processors based on
Intel microarchitecture code name Ivy Bridge, the same holds true.
One difference of note is that MSR_LBR_SELECT is shared between two logical processors in the same core. In Intel
microarchitecture code name Sandy Bridge, each logical processor has its own MSR_LBR_SELECT. The filtering
semantics for “Near_ind_jmp” and “Near_rel_jmp” has been enhanced, see Table 17-12.
Table 17-12. MSR_LBR_SELECT for Intel® microarchitecture code name Sandy Bridge
Bit Field
Bit Offset
Access
Description
CPL_EQ_0
0
R/W
When set, do not capture branches occurring in ring 0
CPL_NEQ_0
1
R/W
When set, do not capture branches occurring in ring >0
JCC
2
R/W
When set, do not capture conditional branches
NEAR_REL_CALL
3
R/W
When set, do not capture near relative calls
NEAR_IND_CALL
4
R/W
When set, do not capture near indirect calls
NEAR_RET
5
R/W
When set, do not capture near returns
NEAR_IND_JMP
6
R/W
When set, do not capture near indirect jumps except near indirect calls and near returns
NEAR_REL_JMP
7
R/W
When set, do not capture near relative jumps except near relative calls.
FAR_BRANCH
8
R/W
When set, do not capture far branches
Reserved
63:9
17.9
Must be zero
LAST BRANCH, CALL STACK, INTERRUPT, AND EXCEPTION RECORDING
FOR PROCESSORS BASED ON HASWELL MICROARCHITECTURE
Generally, all of the last branch record, interrupt and exception recording facility described in Section 17.8, “Last
Branch, Interrupt, and Exception Recording for Processors based on Intel® Microarchitecture code name Sandy
Bridge”, apply to next generation processors based on Intel microarchitecture code name Haswell.
The LBR facility also supports an alternate capability to profile call stack profiles. Configuring the LBR facility to
conduct call stack profiling is by writing 1 to the MSR_LBR_SELECT.EN_CALLSTACK[bit 9]; see Table 17-13. If
MSR_LBR_SELECT.EN_CALLSTACK is clear, the LBR facility will capture branches normally as described in Section
17.8.
Table 17-13. MSR_LBR_SELECT for Intel® microarchitecture code name Haswell
Bit Field
Bit Offset
Access
Description
CPL_EQ_0
0
R/W
When set, do not capture branches occurring in ring 0
CPL_NEQ_0
1
R/W
When set, do not capture branches occurring in ring >0
JCC
2
R/W
When set, do not capture conditional branches
NEAR_REL_CALL
3
R/W
When set, do not capture near relative calls
NEAR_IND_CALL
4
R/W
When set, do not capture near indirect calls
NEAR_RET
5
R/W
When set, do not capture near returns
NEAR_IND_JMP
6
R/W
When set, do not capture near indirect jumps except near indirect calls and near returns
NEAR_REL_JMP
7
R/W
When set, do not capture near relative jumps except near relative calls.
Vol. 3B 17-29
DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
Table 17-13. MSR_LBR_SELECT for Intel® microarchitecture code name Haswell
Bit Field
FAR_BRANCH
1
Bit Offset
Access
Description
8
R/W
When set, do not capture far branches
EN_CALLSTACK
9
Enable LBR stack to use LIFO filtering to capture Call stack profile
Reserved
63:10
Must be zero
NOTES:
1. Must set valid combination of bits 0-8 in conjunction with bit 9 (as described below), otherwise the contents of the LBR MSRs are
undefined.
The call stack profiling capability is an enhancement of the LBR facility. The LBR stack is a ring buffer typically used
to profile control flow transitions resulting from branches. However, the finite depth of the LBR stack often become
less effective when profiling certain high-level languages (e.g. C++), where a transition of the execution flow is
accompanied by a large number of leaf function calls, each of which returns an individual parameter to form the list
of parameters for the main execution function call. A long list of such parameters returned by the leaf functions
would serve to flush the data captured in the LBR stack, often losing the main execution context.
When the call stack feature is enabled, the LBR stack will capture unfiltered call data normally, but as return
instructions are executed the last captured branch record is flushed from the on-chip registers in a last-in first-out
(LIFO) manner. Thus, branch information relative to leaf functions will not be captured, while preserving the call
stack information of the main line execution path.
The configuration of the call stack facility is summarized below:
•
Set IA32_DEBUGCTL.LBR (bit 0) to enable the LBR stack to capture branch records. The source and target
addresses of the call branches will be captured in the 16 pairs of From/To LBR MSRs that form the LBR stack.
•
Program the Top of Stack (TOS) MSR that points to the last valid from/to pair. This register is incremented by
1, modulo 16, before recording the next pair of addresses.
•
•
Program the branch filtering bits of MSR_LBR_SELECT (bits 0:8) as desired.
Program the MSR_LBR_SELECT to enable LIFO filtering of return instructions with:
— The following bits in MSR_LBR_SELECT must be set to ‘1’: JCC, NEAR_IND_JMP, NEAR_REL_JMP,
FAR_BRANCH, EN_CALLSTACK;
— The following bits in MSR_LBR_SELECT must be cleared: NEAR_REL_CALL, NEAR-IND_CALL, NEAR_RET;
— At most one of CPL_EQ_0, CPL_NEQ_0 is set.
Note that when call stack profiling is enabled, “zero length calls” are excluded from writing into the LBRs. (A “zero
length call” uses the attribute of the call instruction to push the immediate instruction pointer on to the stack and
then pops off that address into a register. This is accomplished without any matching return on the call.)
17.9.1
LBR Stack Enhancement
Processors based on Intel microarchitecture code name Haswell provide 16 pairs of MSR to record last branch
record information. The layout of each MSR pair is enumerated by IA32_PERF_CAPABILITIES[5:0] = 04H, and is
shown in Table 17-14 and Table 17-9.
Table 17-14. MSR_LASTBRANCH_x_FROM_IP with TSX Information
Bit Field
Bit Offset
Access
Description
Data
47:0
R/O
This is the “branch from“ address. See Section 17.4.8.1 for address format.
SIGN_EXT
60:48
R/0
Signed extension of bit 47 of this register.
TSX_ABORT
61
R/0
When set, indicates a TSX Abort entry
LBR_FROM: EIP at the time of the TSX Abort
LBR_TO: EIP of the start of HLE region, or EIP of the RTM Abort Handler
IN_TSX
62
R/0
When set, indicates the entry occurred in a TSX region
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
Table 17-14. MSR_LASTBRANCH_x_FROM_IP with TSX Information (Contd.)
Bit Field
Bit Offset
Access
Description
MISPRED
63
R/O
When set, indicates either the target of the branch was mispredicted and/or the
direction (taken/non-taken) was mispredicted; otherwise, the target branch was
predicted.
17.10
LAST BRANCH, CALL STACK, INTERRUPT, AND EXCEPTION RECORDING
FOR PROCESSORS BASED ON SKYLAKE MICROARCHITECTURE
Processors based on the Skylake microarchitecture provide a number of enhancement with storing last branch
records:
•
enumeration of new LBR format: encoding 00101b in IA32_PERF_CAPABILITIES[5:0] is supported, see Section
17.4.8.1.
•
Each LBR stack entry consists of a triplets of MSRs:
— MSR_LASTBRANCH_x_FROM_IP, the layout is simplified, see Table 17-9.
— MSR_LASTBRANCH_x_TO_IP, the layout is the same as Table 17-9.
— MSR_LBR_INFO_x, stores branch prediction flag, TSX info, and elapsed cycle data.
•
Size of LBR stack increased to 32.
Processors based on the Skylake microarchitecture supports the same LBR filtering capabilities as described in
Table 17-13.
Table 17-15. LBR Stack Size and TOS Pointer Range
DisplayFamily_DisplayModel
Size of LBR Stack
Range of TOS Pointer
06_4EH, 06_5EH
32
0 to 31
17.10.1
MSR_LBR_INFO_x MSR
The layout of each MSR_LBR_INFO_x MSR is shown in Table 17-16.
Table 17-16. MSR_LBR_INFO_x
Bit Field
Bit Offset
Access
Description
Cycle Count
(saturating)
15:0
R/O
Elapsed core clocks since last update to the LBR stack
Reserved
60:16
R/O
Reserved
TSX_ABORT
61
R/0
When set, indicates a TSX Abort entry
LBR_FROM: EIP at the time of the TSX Abort
LBR_TO: EIP of the start of HLE region OR
EIP of the RTM Abort Handler
IN_TSX
62
R/0
When set, indicates the entry occurred in a TSX region.
MISPRED
63
R/O
When set, indicates either the target of the branch was mispredicted and/or the
direction (taken/non-taken) was mispredicted; otherwise, the target branch was
predicted.
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
17.10.2
Streamlined Freeze_LBRs_On_PMI Operation
The capability to freeze the content of LBR to maintain recorded data quality continues to use the same interface
IA32_DEBUGCTL.Freeze_LBRs_ON_PMI. Architectural performance monitoring version 4 and above supports a
streamlined Freeze_LBRs_ON_PMI operation for PMI service routine that replaces the legacy
Freeze_LBRs_ON_PMI operation (see Section 17.4.7).
Table 17-17 compares the interaction of the processor with the PMI handler.
Table 17-17. Legacy and Streamlined Operation with Freeze_LBRs_On_PMI = 1, Buffer Full
Legacy Freeze_LBRs_On_PMI
Streamlined Freeze_LBRs_On_PMI
Comment
Processor freezes the LBR stack on PEBS buffer full Processor freezes the LBR stack on PEBS buffer full Unchanged
Processor clears IA32_DEBUGCTRL.LBR (0x1D9)
Processor set
IA32_PERF_GLOBAL_STATUS.LBR_Frz
dbgmask = RDMSR(0x1D9)
mask = RDMSR(0x38E)
Handler services the PMI
Handler services the PMI
Updates dbgmask to include LBR for subsequent
write to IA32_DEBUGCTL
Handler writes mask into
IA32_PERF_GLOBAL_OVF_RESET (0x390)
NA
Processor clears IA32_PERF_GLOBAL_STATUS
Handler writes dbgmask to re-enables
IA32_DEBUGCTL.LBR
NA
17.10.3
Unchanged
Prevents race condition of
MSR 0x1D9 being updated
by the processor and
handler
LBR Behavior and Deep C-State
When MWAIT is used to request a C-state that is numerically higher than C1, then LBR state may be initialized to
zero depending on optimized “waiting” state that is selected by the processor The affected LBR states include the
FROM, TO, INFO, LAST_BRANCH, LER and LBR_TOS registers. The LBR enable bit and LBR_FROZEN bit are not
affected. The LBR-time of the first LBR record inserted after an exit from such a C-state request will be zero.
17.11
LAST BRANCH, INTERRUPT, AND EXCEPTION RECORDING (PROCESSORS
BASED ON INTEL NETBURST® MICROARCHITECTURE)
Pentium 4 and Intel Xeon processors based on Intel NetBurst microarchitecture provide the following methods for
recording taken branches, interrupts and exceptions:
•
Store branch records in the last branch record (LBR) stack MSRs for the most recent taken branches,
interrupts, and/or exceptions in MSRs. A branch record consist of a branch-from and a branch-to instruction
address.
•
•
Send the branch records out on the system bus as branch trace messages (BTMs).
Log BTMs in a memory-resident branch trace store (BTS) buffer.
To support these functions, the processor provides the following MSRs and related facilities:
•
MSR_DEBUGCTLA MSR — Enables last branch, interrupt, and exception recording; single-stepping on taken
branches; branch trace messages (BTMs); and branch trace store (BTS). This register is named DebugCtlMSR
in the P6 family processors.
•
Debug store (DS) feature flag (CPUID.1:EDX.DS[bit 21]) — Indicates that the processor provides the
debug store (DS) mechanism, which allows BTMs to be stored in a memory-resident BTS buffer.
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
•
CPL-qualified debug store (DS) feature flag (CPUID.1:ECX.DS-CPL[bit 4]) — Indicates that the
processor provides a CPL-qualified debug store (DS) mechanism, which allows software to selectively skip
sending and storing BTMs, according to specified current privilege level settings, into a memory-resident BTS
buffer.
•
•
IA32_MISC_ENABLE MSR — Indicates that the processor provides the BTS facilities.
•
Last branch record top-of-stack (TOS) pointer — The TOS Pointer MSR contains a 2-bit pointer (0-3) to
the MSR in the LBR stack that contains the most recent branch, interrupt, or exception recorded for the
Pentium 4 and Intel Xeon processor family [CPUID family 0FH, models 0H-02H]. This pointer becomes a 4-bit
pointer (0-15) for the Pentium 4 and Intel Xeon processor family [CPUID family 0FH, model 03H]. See also:
Table 17-18, Figure 17-12, and Section 17.11.2, “LBR Stack for Processors Based on Intel NetBurst® Microarchitecture.”
•
Last exception record — See Section 17.11.3, “Last Exception Records.”
Last branch record (LBR) stack — The LBR stack is a circular stack that consists of four MSRs
(MSR_LASTBRANCH_0 through MSR_LASTBRANCH_3) for the Pentium 4 and Intel Xeon processor family
[CPUID family 0FH, models 0H-02H]. The LBR stack consists of 16 MSR pairs
(MSR_LASTBRANCH_0_FROM_IP through MSR_LASTBRANCH_15_FROM_IP and
MSR_LASTBRANCH_0_TO_IP through MSR_LASTBRANCH_15_TO_IP) for the Pentium 4 and Intel Xeon
processor family [CPUID family 0FH, model 03H].
17.11.1
MSR_DEBUGCTLA MSR
The MSR_DEBUGCTLA MSR enables and disables the various last branch recording mechanisms described in the
previous section. This register can be written to using the WRMSR instruction, when operating at privilege level 0
or when in real-address mode. A protected-mode operating system procedure is required to provide user access to
this register. Figure 17-12 shows the flags in the MSR_DEBUGCTLA MSR. The functions of these flags are as
follows:
•
LBR (last branch/interrupt/exception) flag (bit 0) — When set, the processor records a running trace of
the most recent branches, interrupts, and/or exceptions taken by the processor (prior to a debug exception
being generated) in the last branch record (LBR) stack. Each branch, interrupt, or exception is recorded as a
64-bit branch record. The processor clears this flag whenever a debug exception is generated (for example,
when an instruction or data breakpoint or a single-step trap occurs). See Section 17.11.2, “LBR Stack for
Processors Based on Intel NetBurst® Microarchitecture.”
•
BTF (single-step on branches) flag (bit 1) — When set, the processor treats the TF flag in the EFLAGS
register as a “single-step on branches” flag rather than a “single-step on instructions” flag. This mechanism
allows single-stepping the processor on taken branches. See Section 17.4.3, “Single-Stepping on Branches.”
•
TR (trace message enable) flag (bit 2) — When set, branch trace messages are enabled. Thereafter, when
the processor detects a taken branch, interrupt, or exception, it sends the branch record out on the system bus
as a branch trace message (BTM). See Section 17.4.4, “Branch Trace Messages.”
31
7 6 5 4 3 2 1 0
Reserved
BTS_OFF_USR — Disable storing non-CPL_0 BTS
BTS_OFF_OS — Disable storing CPL_0 BTS
BTINT — Branch trace interrupt
BTS — Branch trace store
TR — Trace messages enable
BTF — Single-step on branches
LBR — Last branch/interrupt/exception
Figure 17-12. MSR_DEBUGCTLA MSR for Pentium 4 and Intel Xeon Processors
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
•
BTS (branch trace store) flag (bit 3) — When set, enables the BTS facilities to log BTMs to a memoryresident BTS buffer that is part of the DS save area. See Section 17.4.9, “BTS and DS Save Area.”
•
BTINT (branch trace interrupt) flag (bits 4) — When set, the BTS facilities generate an interrupt when the
BTS buffer is full. When clear, BTMs are logged to the BTS buffer in a circular fashion. See Section 17.4.5, “Branch
Trace Store (BTS).”
•
BTS_OFF_OS (disable ring 0 branch trace store) flag (bit 5) — When set, enables the BTS facilities to
skip sending/logging CPL_0 BTMs to the memory-resident BTS buffer. See Section 17.11.2, “LBR Stack for
Processors Based on Intel NetBurst® Microarchitecture.”
•
BTS_OFF_USR (disable ring 0 branch trace store) flag (bit 6) — When set, enables the BTS facilities to
skip sending/logging non-CPL_0 BTMs to the memory-resident BTS buffer. See Section 17.11.2, “LBR Stack for
Processors Based on Intel NetBurst® Microarchitecture.”
NOTE
The initial implementation of BTS_OFF_USR and BTS_OFF_OS in MSR_DEBUGCTLA is shown in
Figure 17-12. The BTS_OFF_USR and BTS_OFF_OS fields may be implemented on other modelspecific debug control register at different locations.
See Chapter 35, “Model-Specific Registers (MSRs),” for a detailed description of each of the last branch recording
MSRs.
17.11.2
LBR Stack for Processors Based on Intel NetBurst® Microarchitecture
The LBR stack is made up of LBR MSRs that are treated by the processor as a circular stack. The TOS pointer
(MSR_LASTBRANCH_TOS MSR) points to the LBR MSR (or LBR MSR pair) that contains the most recent (last)
branch record placed on the stack. Prior to placing a new branch record on the stack, the TOS is incremented by 1.
When the TOS pointer reaches it maximum value, it wraps around to 0. See Table 17-18 and Figure 17-12.
Table 17-18. LBR MSR Stack Size and TOS Pointer Range for the Pentium® 4 and the Intel® Xeon® Processor Family
DisplayFamily_DisplayModel
Size of LBR Stack
Range of TOS Pointer
Family 0FH, Models 0H-02H; MSRs at locations 1DBH-1DEH.
4
0 to 3
Family 0FH, Models; MSRs at locations 680H-68FH.
16
0 to 15
Family 0FH, Model 03H; MSRs at locations 6C0H-6CFH.
16
0 to 15
The registers in the LBR MSR stack and the MSR_LASTBRANCH_TOS MSR are read-only and can be read using the
RDMSR instruction.
Figure 17-13 shows the layout of a branch record in an LBR MSR (or MSR pair). Each branch record consists of two
linear addresses, which represent the “from” and “to” instruction pointers for a branch, interrupt, or exception. The
contents of the from and to addresses differ, depending on the source of the branch:
•
Taken branch — If the record is for a taken branch, the “from” address is the address of the branch instruction
and the “to” address is the target instruction of the branch.
•
Interrupt — If the record is for an interrupt, the “from” address the return instruction pointer (RIP) saved for
the interrupt and the “to” address is the address of the first instruction in the interrupt handler routine. The RIP
is the linear address of the next instruction to be executed upon returning from the interrupt handler.
•
Exception — If the record is for an exception, the “from” address is the linear address of the instruction that
caused the exception to be generated and the “to” address is the address of the first instruction in the exception
handler routine.
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
CPUID Family 0FH, Models 0H-02H
MSR_LASTBRANCH_0 through MSR_LASTBRANCH_3
63
0
32 - 31
From Linear Address
To Linear Address
CPUID Family 0FH, Model 03H-04H
MSR_LASTBRANCH_0_FROM_IP through MSR_LASTBRANCH_15_FROM_IP
0
32 - 31
63
Reserved
From Linear Address
MSR_LASTBRANCH_0_TO_IP through MSR_LASTBRANCH_15_TO_IP
63
0
32 - 31
Reserved
To Linear Address
Figure 17-13. LBR MSR Branch Record Layout for the Pentium 4
and Intel Xeon Processor Family
Additional information is saved if an exception or interrupt occurs in conjunction with a branch instruction. If a
branch instruction generates a trap type exception, two branch records are stored in the LBR stack: a branch
record for the branch instruction followed by a branch record for the exception.
If a branch instruction is immediately followed by an interrupt, a branch record is stored in the LBR stack for the
branch instruction followed by a record for the interrupt.
17.11.3
Last Exception Records
The Pentium 4, Intel Xeon, Pentium M, Intel® Core™ Solo, Intel® Core™ Duo, Intel® Core™2 Duo, Intel® Core™ i7
and Intel® Atom™ processors provide two MSRs (the MSR_LER_TO_LIP and the MSR_LER_FROM_LIP MSRs) that
duplicate the functions of the LastExceptionToIP and LastExceptionFromIP MSRs found in the P6 family processors.
The MSR_LER_TO_LIP and MSR_LER_FROM_LIP MSRs contain a branch record for the last branch that the
processor took prior to an exception or interrupt being generated.
17.12
LAST BRANCH, INTERRUPT, AND EXCEPTION RECORDING (INTEL® CORE™
SOLO AND INTEL® CORE™ DUO PROCESSORS)
Intel Core Solo and Intel Core Duo processors provide last branch interrupt and exception recording. This capability
is almost identical to that found in Pentium 4 and Intel Xeon processors. There are differences in the stack and in
some MSR names and locations.
Note the following:
•
IA32_DEBUGCTL MSR — Enables debug trace interrupt, debug trace store, trace messages enable,
performance monitoring breakpoint flags, single stepping on branches, and last branch. IA32_DEBUGCTL MSR
is located at register address 01D9H.
See Figure 17-14 for the layout and the entries below for a description of the flags:
— LBR (last branch/interrupt/exception) flag (bit 0) — When set, the processor records a running trace
of the most recent branches, interrupts, and/or exceptions taken by the processor (prior to a debug
exception being generated) in the last branch record (LBR) stack. For more information, see the “Last
Branch Record (LBR) Stack” below.
— BTF (single-step on branches) flag (bit 1) — When set, the processor treats the TF flag in the EFLAGS
register as a “single-step on branches” flag rather than a “single-step on instructions” flag. This mechanism
Vol. 3B 17-35
DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
allows single-stepping the processor on taken branches. See Section 17.4.3, “Single-Stepping on
Branches,” for more information about the BTF flag.
— TR (trace message enable) flag (bit 6) — When set, branch trace messages are enabled. When the
processor detects a taken branch, interrupt, or exception; it sends the branch record out on the system bus
as a branch trace message (BTM). See Section 17.4.4, “Branch Trace Messages,” for more information
about the TR flag.
— BTS (branch trace store) flag (bit 7) — When set, the flag enables BTS facilities to log BTMs to a
memory-resident BTS buffer that is part of the DS save area. See Section 17.4.9, “BTS and DS Save Area.”
— BTINT (branch trace interrupt) flag (bits 8) — When set, the BTS facilities generate an interrupt when
the BTS buffer is full. When clear, BTMs are logged to the BTS buffer in a circular fashion. See Section 17.4.5,
“Branch Trace Store (BTS),” for a description of this mechanism.
31
8 7 6 5 4 3 2 1 0
Reserved
BTINT — Branch trace interrupt
BTS — Branch trace store
TR — Trace messages enable
Reserved
BTF — Single-step on branches
LBR — Last branch/interrupt/exception
Figure 17-14. IA32_DEBUGCTL MSR for Intel Core Solo
and Intel Core Duo Processors
•
Debug store (DS) feature flag (bit 21), returned by the CPUID instruction — Indicates that the
processor provides the debug store (DS) mechanism, which allows BTMs to be stored in a memory-resident
BTS buffer. See Section 17.4.5, “Branch Trace Store (BTS).”
•
Last Branch Record (LBR) Stack — The LBR stack consists of 8 MSRs (MSR_LASTBRANCH_0 through
MSR_LASTBRANCH_7); bits 31-0 hold the ‘from’ address, bits 63-32 hold the ‘to’ address (MSR addresses start
at 40H). See Figure 17-15.
•
Last Branch Record Top-of-Stack (TOS) Pointer — The TOS Pointer MSR contains a 3-bit pointer (bits 2-0)
to the MSR in the LBR stack that contains the most recent branch, interrupt, or exception recorded. For Intel
Core Solo and Intel Core Duo processors, this MSR is located at register address 01C9H.
For compatibility, the Intel Core Solo and Intel Core Duo processors provide two 32-bit MSRs (the
MSR_LER_TO_LIP and the MSR_LER_FROM_LIP MSRs) that duplicate functions of the LastExceptionToIP and LastExceptionFromIP MSRs found in P6 family processors.
For details, see Section 17.10, “Last Branch, Call Stack, Interrupt, and Exception Recording for Processors based
on Skylake Microarchitecture,” and Section 35.19, “MSRs In Intel® Core™ Solo and Intel® Core™ Duo Processors”
MSR_LASTBRANCH_0 through MSR_LASTBRANCH_7
63
0
32 - 31
To Linear Address
From Linear Address
Figure 17-15. LBR Branch Record Layout for the Intel Core Solo
and Intel Core Duo Processor
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
17.13
LAST BRANCH, INTERRUPT, AND EXCEPTION
RECORDING (PENTIUM M PROCESSORS)
Like the Pentium 4 and Intel Xeon processor family, Pentium M processors provide last branch interrupt and exception recording. The capability operates almost identically to that found in Pentium 4 and Intel Xeon processors.
There are differences in the shape of the stack and in some MSR names and locations. Note the following:
•
MSR_DEBUGCTLB MSR — Enables debug trace interrupt, debug trace store, trace messages enable,
performance monitoring breakpoint flags, single stepping on branches, and last branch. For Pentium M
processors, this MSR is located at register address 01D9H. See Figure 17-16 and the entries below for a
description of the flags.
— LBR (last branch/interrupt/exception) flag (bit 0) — When set, the processor records a running trace
of the most recent branches, interrupts, and/or exceptions taken by the processor (prior to a debug
exception being generated) in the last branch record (LBR) stack. For more information, see the “Last
Branch Record (LBR) Stack” bullet below.
— BTF (single-step on branches) flag (bit 1) — When set, the processor treats the TF flag in the EFLAGS
register as a “single-step on branches” flag rather than a “single-step on instructions” flag. This mechanism
allows single-stepping the processor on taken branches. See Section 17.4.3, “Single-Stepping on
Branches,” for more information about the BTF flag.
— PBi (performance monitoring/breakpoint pins) flags (bits 5-2) — When these flags are set, the
performance monitoring/breakpoint pins on the processor (BP0#, BP1#, BP2#, and BP3#) report
breakpoint matches in the corresponding breakpoint-address registers (DR0 through DR3). The processor
asserts then deasserts the corresponding BPi# pin when a breakpoint match occurs. When a PBi flag is
clear, the performance monitoring/breakpoint pins report performance events. Processor execution is not
affected by reporting performance events.
— TR (trace message enable) flag (bit 6) — When set, branch trace messages are enabled. When the
processor detects a taken branch, interrupt, or exception, it sends the branch record out on the system bus
as a branch trace message (BTM). See Section 17.4.4, “Branch Trace Messages,” for more information
about the TR flag.
— BTS (branch trace store) flag (bit 7) — When set, enables the BTS facilities to log BTMs to a memoryresident BTS buffer that is part of the DS save area. See Section 17.4.9, “BTS and DS Save Area.”
— BTINT (branch trace interrupt) flag (bits 8) — When set, the BTS facilities generate an interrupt when
the BTS buffer is full. When clear, BTMs are logged to the BTS buffer in a circular fashion. See Section 17.4.5,
“Branch Trace Store (BTS),” for a description of this mechanism.
31
8 7 6 5 4 3 2 1 0
Reserved
BTINT — Branch trace interrupt
BTS — Branch trace store
TR — Trace messages enable
PB3/2/1/0 — Performance monitoring breakpoint flags
BTF — Single-step on branches
LBR — Last branch/interrupt/exception
Figure 17-16. MSR_DEBUGCTLB MSR for Pentium M Processors
•
Debug store (DS) feature flag (bit 21), returned by the CPUID instruction — Indicates that the
processor provides the debug store (DS) mechanism, which allows BTMs to be stored in a memory-resident
BTS buffer. See Section 17.4.5, “Branch Trace Store (BTS).”
Vol. 3B 17-37
DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
•
Last Branch Record (LBR) Stack — The LBR stack consists of 8 MSRs (MSR_LASTBRANCH_0 through
MSR_LASTBRANCH_7); bits 31-0 hold the ‘from’ address, bits 63-32 hold the ‘to’ address. For Pentium M
Processors, these pairs are located at register addresses 040H-047H. See Figure 17-17.
•
Last Branch Record Top-of-Stack (TOS) Pointer — The TOS Pointer MSR contains a 3-bit pointer (bits 2-0)
to the MSR in the LBR stack that contains the most recent branch, interrupt, or exception recorded. For Pentium
M Processors, this MSR is located at register address 01C9H.
MSR_LASTBRANCH_0
through MSR_LASTBRANCH_7
0
32 - 31
63
To Linear Address
From Linear Address
Figure 17-17. LBR Branch Record Layout for the Pentium M Processor
For more detail on these capabilities, see Section 17.11.3, “Last Exception Records,” and Section 35.20, “MSRs In
the Pentium M Processor.”
17.14
LAST BRANCH, INTERRUPT, AND EXCEPTION
RECORDING (P6 FAMILY PROCESSORS)
The P6 family processors provide five MSRs for recording the last branch, interrupt, or exception taken by the
processor: DEBUGCTLMSR, LastBranchToIP, LastBranchFromIP, LastExceptionToIP, and LastExceptionFromIP.
These registers can be used to collect last branch records, to set breakpoints on branches, interrupts, and exceptions, and to single-step from one branch to the next.
See Chapter 35, “Model-Specific Registers (MSRs),” for a detailed description of each of the last branch recording
MSRs.
17.14.1
DEBUGCTLMSR Register
The version of the DEBUGCTLMSR register found in the P6 family processors enables last branch, interrupt, and
exception recording; taken branch breakpoints; the breakpoint reporting pins; and trace messages. This register
can be written to using the WRMSR instruction, when operating at privilege level 0 or when in real-address mode.
A protected-mode operating system procedure is required to provide user access to this register. Figure 17-18
shows the flags in the DEBUGCTLMSR register for the P6 family processors. The functions of these flags are as
follows:
•
LBR (last branch/interrupt/exception) flag (bit 0) — When set, the processor records the source and
target addresses (in the LastBranchToIP, LastBranchFromIP, LastExceptionToIP, and LastExceptionFromIP
MSRs) for the last branch and the last exception or interrupt taken by the processor prior to a debug exception
being generated. The processor clears this flag whenever a debug exception, such as an instruction or data
breakpoint or single-step trap occurs.
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
31
7 6 5 4 3 2 1 0
Reserved
P P P P B L
T B B B B T B
R 3 2 1 0 F R
TR — Trace messages enable
PBi — Performance monitoring/breakpoint pins
BTF — Single-step on branches
LBR — Last branch/interrupt/exception
Figure 17-18. DEBUGCTLMSR Register (P6 Family Processors)
•
BTF (single-step on branches) flag (bit 1) — When set, the processor treats the TF flag in the EFLAGS
register as a “single-step on branches” flag. See Section 17.4.3, “Single-Stepping on Branches.”
•
PBi (performance monitoring/breakpoint pins) flags (bits 2 through 5) — When these flags are set,
the performance monitoring/breakpoint pins on the processor (BP0#, BP1#, BP2#, and BP3#) report
breakpoint matches in the corresponding breakpoint-address registers (DR0 through DR3). The processor
asserts then deasserts the corresponding BPi# pin when a breakpoint match occurs. When a PBi flag is clear,
the performance monitoring/breakpoint pins report performance events. Processor execution is not affected by
reporting performance events.
•
TR (trace message enable) flag (bit 6) — When set, trace messages are enabled as described in Section
17.4.4, “Branch Trace Messages.” Setting this flag greatly reduces the performance of the processor. When
trace messages are enabled, the values stored in the LastBranchToIP, LastBranchFromIP, LastExceptionToIP,
and LastExceptionFromIP MSRs are undefined.
17.14.2
Last Branch and Last Exception MSRs
The LastBranchToIP and LastBranchFromIP MSRs are 32-bit registers for recording the instruction pointers for the
last branch, interrupt, or exception that the processor took prior to a debug exception being generated. When a
branch occurs, the processor loads the address of the branch instruction into the LastBranchFromIP MSR and loads
the target address for the branch into the LastBranchToIP MSR.
When an interrupt or exception occurs (other than a debug exception), the address of the instruction that was
interrupted by the exception or interrupt is loaded into the LastBranchFromIP MSR and the address of the exception or interrupt handler that is called is loaded into the LastBranchToIP MSR.
The LastExceptionToIP and LastExceptionFromIP MSRs (also 32-bit registers) record the instruction pointers for
the last branch that the processor took prior to an exception or interrupt being generated. When an exception or
interrupt occurs, the contents of the LastBranchToIP and LastBranchFromIP MSRs are copied into these registers
before the to and from addresses of the exception or interrupt are recorded in the LastBranchToIP and LastBranchFromIP MSRs.
These registers can be read using the RDMSR instruction.
Note that the values stored in the LastBranchToIP, LastBranchFromIP, LastExceptionToIP, and LastExceptionFromIP
MSRs are offsets into the current code segment, as opposed to linear addresses, which are saved in last branch
records for the Pentium 4 and Intel Xeon processors.
17.14.3
Monitoring Branches, Exceptions, and Interrupts
When the LBR flag in the DEBUGCTLMSR register is set, the processor automatically begins recording branches
that it takes, exceptions that are generated (except for debug exceptions), and interrupts that are serviced. Each
time a branch, exception, or interrupt occurs, the processor records the to and from instruction pointers in the
LastBranchToIP and LastBranchFromIP MSRs. In addition, for interrupts and exceptions, the processor copies the
contents of the LastBranchToIP and LastBranchFromIP MSRs into the LastExceptionToIP and LastExceptionFromIP
MSRs prior to recording the to and from addresses of the interrupt or exception.
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
When the processor generates a debug exception (#DB), it automatically clears the LBR flag before executing the
exception handler, but does not touch the last branch and last exception MSRs. The addresses for the last branch,
interrupt, or exception taken are thus retained in the LastBranchToIP and LastBranchFromIP MSRs and the
addresses of the last branch prior to an interrupt or exception are retained in the LastExceptionToIP, and LastExceptionFromIP MSRs.
The debugger can use the last branch, interrupt, and/or exception addresses in combination with code-segment
selectors retrieved from the stack to reset breakpoints in the breakpoint-address registers (DR0 through DR3),
allowing a backward trace from the manifestation of a particular bug toward its source. Because the instruction
pointers recorded in the LastBranchToIP, LastBranchFromIP, LastExceptionToIP, and LastExceptionFromIP MSRs are
offsets into a code segment, software must determine the segment base address of the code segment associated
with the control transfer to calculate the linear address to be placed in the breakpoint-address registers. The
segment base address can be determined by reading the segment selector for the code segment from the stack
and using it to locate the segment descriptor for the segment in the GDT or LDT. The segment base address can
then be read from the segment descriptor.
Before resuming program execution from a debug-exception handler, the handler must set the LBR flag again to reenable last branch and last exception/interrupt recording.
17.15
TIME-STAMP COUNTER
The Intel 64 and IA-32 architectures (beginning with the Pentium processor) define a time-stamp counter mechanism that can be used to monitor and identify the relative time occurrence of processor events. The counter’s architecture includes the following components:
•
TSC flag — A feature bit that indicates the availability of the time-stamp counter. The counter is available in an
if the function CPUID.1:EDX.TSC[bit 4] = 1.
•
IA32_TIME_STAMP_COUNTER MSR (called TSC MSR in P6 family and Pentium processors) — The MSR used
as the counter.
•
•
RDTSC instruction — An instruction used to read the time-stamp counter.
TSD flag — A control register flag is used to enable or disable the time-stamp counter (enabled if
CR4.TSD[bit 2] = 1).
The time-stamp counter (as implemented in the P6 family, Pentium, Pentium M, Pentium 4, Intel Xeon, Intel Core
Solo and Intel Core Duo processors and later processors) is a 64-bit counter that is set to 0 following a RESET of
the processor. Following a RESET, the counter increments even when the processor is halted by the HLT instruction
or the external STPCLK# pin. Note that the assertion of the external DPSLP# pin may cause the time-stamp
counter to stop.
Processor families increment the time-stamp counter differently:
•
For Pentium M processors (family [06H], models [09H, 0DH]); for Pentium 4 processors, Intel Xeon processors
(family [0FH], models [00H, 01H, or 02H]); and for P6 family processors: the time-stamp counter increments
with every internal processor clock cycle.
The internal processor clock cycle is determined by the current core-clock to bus-clock ratio. Intel®
SpeedStep® technology transitions may also impact the processor clock.
•
For Pentium 4 processors, Intel Xeon processors (family [0FH], models [03H and higher]); for Intel Core Solo
and Intel Core Duo processors (family [06H], model [0EH]); for the Intel Xeon processor 5100 series and Intel
Core 2 Duo processors (family [06H], model [0FH]); for Intel Core 2 and Intel Xeon processors (family [06H],
DisplayModel [17H]); for Intel Atom processors (family [06H],
DisplayModel [1CH]): the time-stamp counter increments at a constant rate. That rate may be set by the
maximum core-clock to bus-clock ratio of the processor or may be set by the maximum resolved frequency at
which the processor is booted. The maximum resolved frequency may differ from the processor base
frequency, see Section 18.16.5 for more detail. On certain processors, the TSC frequency may not be the same
as the frequency in the brand string.
The specific processor configuration determines the behavior. Constant TSC behavior ensures that the duration
of each clock tick is uniform and supports the use of the TSC as a wall clock timer even if the processor core
changes frequency. This is the architectural behavior moving forward.
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NOTE
To determine average processor clock frequency, Intel recommends the use of performance
monitoring logic to count processor core clocks over the period of time for which the average is
required. See Section 18.16, “Counting Clocks,” and Chapter 19, “Performance-Monitoring Events,”
for more information.
The RDTSC instruction reads the time-stamp counter and is guaranteed to return a monotonically increasing
unique value whenever executed, except for a 64-bit counter wraparound. Intel guarantees that the time-stamp
counter will not wraparound within 10 years after being reset. The period for counter wrap is longer for Pentium 4,
Intel Xeon, P6 family, and Pentium processors.
Normally, the RDTSC instruction can be executed by programs and procedures running at any privilege level and in
virtual-8086 mode. The TSD flag allows use of this instruction to be restricted to programs and procedures running
at privilege level 0. A secure operating system would set the TSD flag during system initialization to disable user
access to the time-stamp counter. An operating system that disables user access to the time-stamp counter should
emulate the instruction through a user-accessible programming interface.
The RDTSC instruction is not serializing or ordered with other instructions. It does not necessarily wait until all
previous instructions have been executed before reading the counter. Similarly, subsequent instructions may begin
execution before the RDTSC instruction operation is performed.
The RDMSR and WRMSR instructions read and write the time-stamp counter, treating the time-stamp counter as
an ordinary MSR (address 10H). In the Pentium 4, Intel Xeon, and P6 family processors, all 64-bits of the timestamp counter are read using RDMSR (just as with RDTSC). When WRMSR is used to write the time-stamp counter
on processors before family [0FH], models [03H, 04H]: only the low-order 32-bits of the time-stamp counter can
be written (the high-order 32 bits are cleared to 0). For family [0FH], models [03H, 04H, 06H]; for family [06H]],
model [0EH, 0FH]; for family [06H]], DisplayModel [17H, 1AH, 1CH, 1DH]: all 64 bits are writable.
17.15.1
Invariant TSC
The time stamp counter in newer processors may support an enhancement, referred to as invariant TSC.
Processor’s support for invariant TSC is indicated by CPUID.80000007H:EDX[8].
The invariant TSC will run at a constant rate in all ACPI P-, C-. and T-states. This is the architectural behavior
moving forward. On processors with invariant TSC support, the OS may use the TSC for wall clock timer services
(instead of ACPI or HPET timers). TSC reads are much more efficient and do not incur the overhead associated with
a ring transition or access to a platform resource.
17.15.2
IA32_TSC_AUX Register and RDTSCP Support
Processors based on Intel microarchitecture code name Nehalem provide an auxiliary TSC register, IA32_TSC_AUX
that is designed to be used in conjunction with IA32_TSC. IA32_TSC_AUX provides a 32-bit field that is initialized
by privileged software with a signature value (for example, a logical processor ID).
The primary usage of IA32_TSC_AUX in conjunction with IA32_TSC is to allow software to read the 64-bit time
stamp in IA32_TSC and signature value in IA32_TSC_AUX with the instruction RDTSCP in an atomic operation.
RDTSCP returns the 64-bit time stamp in EDX:EAX and the 32-bit TSC_AUX signature value in ECX. The atomicity
of RDTSCP ensures that no context switch can occur between the reads of the TSC and TSC_AUX values.
Support for RDTSCP is indicated by CPUID.80000001H:EDX[27]. As with RDTSC instruction, non-ring 0 access is
controlled by CR4.TSD (Time Stamp Disable flag).
User mode software can use RDTSCP to detect if CPU migration has occurred between successive reads of the TSC.
It can also be used to adjust for per-CPU differences in TSC values in a NUMA system.
17.15.3
Time-Stamp Counter Adjustment
Software can modify the value of the time-stamp counter (TSC) of a logical processor by using the WRMSR instruction to write to the IA32_TIME_STAMP_COUNTER MSR (address 10H). Because such a write applies only to that
Vol. 3B 17-41
DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
logical processor, software seeking to synchronize the TSC values of multiple logical processors must perform these
writes on each logical processor. It may be difficult for software to do this in a way than ensures that all logical
processors will have the same value for the TSC at a given point in time.
The synchronization of TSC adjustment can be simplified by using the 64-bit IA32_TSC_ADJUST MSR (address
3BH). Like the IA32_TIME_STAMP_COUNTER MSR, the IA32_TSC_ADJUST MSR is maintained separately for each
logical processor. A logical processor maintains and uses the IA32_TSC_ADJUST MSR as follows:
•
•
On RESET, the value of the IA32_TSC_ADJUST MSR is 0.
•
If an execution of WRMSR to the IA32_TSC_ADJUST MSR adds (or subtracts) value X from that MSR, the logical
processor also adds (or subtracts) value X from the TSC.
If an execution of WRMSR to the IA32_TIME_STAMP_COUNTER MSR adds (or subtracts) value X from the TSC,
the logical processor also adds (or subtracts) value X from the IA32_TSC_ADJUST MSR.
Unlike the TSC, the value of the IA32_TSC_ADJUST MSR changes only in response to WRMSR (either to the MSR
itself, or to the IA32_TIME_STAMP_COUNTER MSR). Its value does not otherwise change as time elapses. Software
seeking to adjust the TSC can do so by using WRMSR to write the same value to the IA32_TSC_ADJUST MSR on
each logical processor.
Processor support for the IA32_TSC_ADJUST MSR is indicated by CPUID.(EAX=07H, ECX=0H):EBX.TSC_ADJUST
(bit 1).
17.15.4
Invariant Time-Keeping
The invariant TSC is based on the invariant timekeeping hardware (called Always Running Timer or ART), that runs
at the core crystal clock frequency. The ratio defined by CPUID leaf 15H expresses the frequency relationship
between the ART hardware and TSC.
If CPUID.15H:EBX[31:0] != 0 and CPUID.80000007H:EDX[InvariantTSC] = 1, the following linearity relationship
holds between TSC and the ART hardware:
TSC_Value = (ART_Value * CPUID.15H:EBX[31:0] )/ CPUID.15H:EAX[31:0] + K
Where 'K' is an offset that can be adjusted by a privileged agent2.
When ART hardware is reset, both invariant TSC and K are also reset.
17.16
INTEL® RESOURCE DIRECTOR TECHNOLOGY (INTEL® RDT) MONITORING
FEATURES
The Intel Resource Director Technology (Intel RDT) feature set provides a set of monitoring capabilities including
Cache Monitoring Technology (CMT) and Memory Bandwidth Monitoring (MBM). The Intel® Xeon® processor E5 v3
family introduced resource monitoring capability in each logical processor to measure specific platform shared
resource metrics, for example, L3 cache occupancy. The programming interface for these monitoring features is
described in this section. Two features within the monitoring feature set provided are described - Cache Monitoring
Technology (CMT) and Memory Bandwidth Monitoring.
Cache Monitoring Technology (CMT) allows an Operating System, Hypervisor or similar system management agent
to determine the usage of cache by applications running on the platform. The initial implementation is directed at
L3 cache monitoring (currently the last level cache in most server platforms).
Memory Bandwidth Monitoring (MBM), introduced in the Intel® Xeon® processor E5 v4 family, builds on the CMT
infrastructure to allow monitoring of bandwidth from one level of the cache hierarchy to the next - in this case
focusing on the L3 cache, which is typically backed directly by system memory. As a result of this implementation,
memory bandwidth can be monitored.
The monitoring mechanisms described provide the following key shared infrastructure features:
2. IA32_TSC_ADJUST MSR and the TSC-offset field in the VM execution controls of VMCS are some of the common interfaces that privileged software can use to manage the time stamp counter for keeping time
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•
A mechanism to enumerate the presence of the monitoring capabilities within the platform (via a CPUID feature
bit).
•
A framework to enumerate the details of each sub-feature (including CMT and MBM, as discussed later, via
CPUID leaves and sub-leaves).
•
A mechanism for the OS or Hypervisor to indicate a software-defined ID for each of the software threads (applications, virtual machines, etc.) that are scheduled to run on a logical processor. These identifiers are known as
Resource Monitoring IDs (RMIDs).
•
Mechanisms in hardware to monitor cache occupancy and bandwidth statistics as applicable to a given product
generation on a per software-id basis.
•
Mechanisms for the OS or Hypervisor to read back the collected metrics such as L3 occupancy or Memory
Bandwidth for a given software ID at any point during runtime.
17.16.1
Overview of Cache Monitoring Technology and Memory Bandwidth Monitoring
The shared resource monitoring features described in this chapter provide a layer of abstraction between applications and logical processors through the use of Resource Monitoring IDs (RMIDs). Each logical processor in the
system can be assigned an RMID independently, or multiple logical processors can be assigned to the same RMID
value (e.g., to track an application with multiple threads). For each logical processor, only one RMID value is active
at a time. This is enforced by the IA32_PQR_ASSOC MSR, which specifies the active RMID of a logical processor.
Writing to this MSR by software changes the active RMID of the logical processor from an old value to a new value.
The underlying platform shared resource monitoring hardware tracks cache metrics such as cache utilization and
misses as a result of memory accesses according to the RMIDs and reports monitored data via a counter register
(IA32_QM_CTR). The specific event types supported vary by generation and can be enumerated via CPUID. Before
reading back monitored data software must configure an event selection MSR (IA32_QM_EVTSEL) to specify which
metric is to be reported, and the specific RMID for which the data should be returned.
Processor support of the monitoring framework and sub-features such as CMT is reported via the CPUID instruction. The resource type available to the monitoring framework is enumerated via a new leaf function in CPUID.
Reading and writing to the monitoring MSRs requires the RDMSR and WRMSR instructions.
The Cache Monitoring Technology feature set provides the following unique mechanisms:
•
A mechanism to enumerate the presence and details of the CMT feature as applicable to a given level of the
cache hierarchy, independent of other monitoring features.
•
CMT-specific event codes to read occupancy for a given level of the cache hierarchy.
The Memory Bandwidth Monitoring feature provides the following unique mechanisms:
•
A mechanism to enumerate the presence and details of the MBM feature as applicable to a given level of the
cache hierarchy, independent of other monitoring features.
•
MBM-specific event codes to read bandwidth out to the next level of the hierarchy and various sub-event codes
to read more specific metrics as discussed later (e.g., total bandwidth vs. bandwidth only from local memory
controllers on the same package).
17.16.2
Enabling Monitoring: Usage Flow
Figure 17-19 illustrates the key steps for OS/VMM to detect support of shared resource monitoring features such
as CMT and enable resource monitoring for available resource types and monitoring events.
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
On OS/VMM Initialization
PQM Capability
Enumeration
CPUID[
CPUID.(7,0):EBX.12
CPUID.(0FH,0):EDX[31:1]
CPUID.(0FH,1):ECX[31:0]
CPUID.(0FH,1):EDX[31:0]
CPUID.(0FH,1):EBX[31:0]
CPUID.(0FH,0):EBX[31:0]
On Context Switch
Set RMID to monitor
the scheduled app
Periodical Resource
Selection/Reporting
Configure event type
Read monitored data
WRMSR
IA32_PQR_ASSOC.RMID
RDMSR/WRMSR
IA32_QM_EVTSEL
IA32_QM_CTR
Figure 17-19. Platform Shared Resource Monitoring Usage Flow
17.16.3
Enumeration and Detecting Support of Cache Monitoring Technology and Memory
Bandwidth Monitoring
Software can query processor support of shared resource monitoring features capabilities by executing CPUID
instruction with EAX = 07H, ECX = 0H as input. If CPUID.(EAX=07H, ECX=0):EBX.PQM[bit 12] reports 1, the
processor provides the following programming interfaces for shared resource monitoring, including Cache Monitoring Technology:
•
CPUID leaf function 0FH (Shared Resource Monitoring Enumeration leaf) provides information on available
resource types (see Section 17.16.4), and monitoring capabilities for each resource type (see Section 17.16.5).
Note CMT and MBM capabilities are enumerated as separate event vectors using shared enumeration infrastructure under a given resource type.
•
IA32_PQR_ASSOC.RMID: The per-logical-processor MSR, IA32_PQR_ASSOC, that OS/VMM can use to assign
an RMID to each logical processor, see Section 17.16.6.
•
IA32_QM_EVTSEL: This MSR specifies an Event ID (EvtID) and an RMID which the platform uses to look up and
provide monitoring data in the monitoring counter, IA32_QM_CTR, see Section 17.16.7.
•
IA32_QM_CTR: This MSR reports monitored resource data when available along with bits to allow software to
check for error conditions and verify data validity.
Software must follow the following sequence of enumeration to discover Cache Monitoring Technology capabilities:
1. Execute CPUID with EAX=0 to discover the “cpuid_maxLeaf” supported in the processor;
2. If cpuid_maxLeaf >= 7, then execute CPUID with EAX=7, ECX= 0 to verify CPUID.(EAX=07H,
ECX=0):EBX.PQM[bit 12] is set;
3. If CPUID.(EAX=07H, ECX=0):EBX.PQM[bit 12] = 1, then execute CPUID with EAX=0FH, ECX= 0 to query
available resource types that support monitoring;
4. If CPUID.(EAX=0FH, ECX=0):EDX.L3[bit 1] = 1, then execute CPUID with EAX=0FH, ECX= 1 to query the
specific capabilities of L3 Cache Monitoring Technology (CMT) and Memory Bandwidth Monitoring.
5. If CPUID.(EAX=0FH, ECX=0):EDX reports additional resource types supporting monitoring, then execute
CPUID with EAX=0FH, ECX set to a corresponding resource type ID (ResID) as enumerated by the bit position
of CPUID.(EAX=0FH, ECX=0):EDX.
17.16.4
Monitoring Resource Type and Capability Enumeration
CPUID leaf function 0FH (Shared Resource Monitoring Enumeration leaf) provides one sub-leaf (sub-function 0)
that reports shared enumeration infrastructure, and one or more sub-functions that report feature-specific
enumeration data:
•
Monitoring leaf sub-function 0 enumerates available resources that support monitoring, i.e. executing CPUID
with EAX=0FH and ECX=0H. In the initial implementation, L3 cache is the only resource type available. Each
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
supported resource type is represented by a bit in CPUID.(EAX=0FH, ECX=0):EDX[31:1]. The bit position
corresponds to the sub-leaf index (ResID) that software must use to query details of the monitoring capability
of that resource type (see Figure 17-21 and Figure 17-22). Reserved bits of CPUID.(EAX=0FH,
ECX=0):EDX[31:2] correspond to unsupported sub-leaves of the CPUID.0FH leaf. Additionally,
CPUID.(EAX=0FH, ECX=0H):EBX reports the highest RMID value of any resource type that supports
monitoring in the processor.
CPUID.(EAX=0FH, ECX=0H) Output: (EAX: Reserved; ECX: Reserved)
31
EDX
Reserved
2 1
L
3
31
EBX
0
0
Highest RMID Value of Any Resource Type (Zero-Based)
Figure 17-20. CPUID.(EAX=0FH, ECX=0H) Monitoring Resource Type Enumeration
17.16.5
Feature-Specific Enumeration
Each additional sub-leaf of CPUID.(EAX=0FH, ECX=ResID) enumerates the specific details for software to program
Monitoring MSRs using the resource type associated with the given ResID.
Note that in future Monitoring implementations the meanings of the returned registers may vary in other subleaves that are not yet defined. The registers will be specified and defined on a per-ResID basis.
CPUID.(EAX=0FH, ECX=1H) Output: (EAX: Reserved)
31
EBX
0
31
ECX
Upscaling Factor
Upscaling Factor to Total Occupancy (Bytes)
0
Highest RMID Value of This Resource Type (Zero-Based)
MaxRMID
Figure 17-21. L3 Cache Monitoring Capability Enumeration Data (CPUID.(EAX=0FH, ECX=1H) )
For each supported Cache Monitoring resource type, hardware supports only a finite number of RMIDs.
CPUID.(EAX=0FH, ECX=1H).ECX enumerates the highest RMID value that can be monitored with this resource
type, see Figure 17-21.
CPUID.(EAX=0FH, ECX=1H).EDX specifies a bit vector that is used to look up the EventID (See Figure 17-22 and
Table 17-19) that software must program with IA32_QM_EVTSEL in order to retrieve event data. After software
configures IA32_QMEVTSEL with the desired RMID and EventID, it can read the resulting data from IA32_QM_CTR.
The raw numerical value reported from IA32_QM_CTR can be converted to the final value (occupancy in bytes or
bandwidth in bytes per sampled time period) by multiplying the counter value by the value from CPUID.(EAX=0FH,
ECX=1H).EBX, see Figure 17-21.
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
EventTypeBitMask
31
EDX
3 2 1
0
Reserved
L3 Occupancy
L3 Total BW
L3 Local BW
Figure 17-22. L3 Cache Monitoring Capability Enumeration Event Type Bit Vector (CPUID.(EAX=0FH, ECX=1H) )
17.16.5.1 Cache Monitoring Technology
On processors for which Cache Monitoring Technology supports the L3 cache occupancy event, CPUID.(EAX=0FH,
ECX=1H).EDX would return with only bit 0 set. The corresponding event ID can be looked up from Table 17-19. The
L3 occupancy data accumulated in IA32_QM_CTR can be converted to total occupancy (in bytes) by multiplying
with CPUID.(EAX=0FH, ECX=1H).EBX.
Event codes for Cache Monitoring Technology are discussed in the next section.
17.16.5.2 Memory Bandwidth Monitoring
On processors that monitoring supports Memory Bandwidth Monitoring using ResID=1 (L3), two additional bits will
be set in the vector at CPUID.(EAX=0FH, ECX=1H).EDX:
•
CPUID.(EAX=0FH, ECX=1H).EDX[bit 1]: indicates the L3 total external bandwidth monitoring event is
supported if set. This event monitors the L3 total external bandwidth to the next level of the cache hierarchy,
including all demand and prefetch misses from the L3 to the next hierarchy of the memory system. In most
platforms, this represents memory bandwidth.
•
CPUID.(EAX=0FH, ECX=1H).EDX[bit 2]: indicates L3 local memory bandwidth monitoring event is supported if
set. This event monitors the L3 external bandwidth satisfied by the local memory. In most platforms that
support this event, L3 requests are likely serviced by a memory system with non-uniform memory architecture.
This allows bandwidth to off-package memory resources to be tracked by subtracting total from local bandwidth
(for instance, bandwidth over QPI to a memory controller on another physical processor could be tracked by
subtraction).
The corresponding Event ID can be looked up from Table 17-19. The L3 bandwidth data accumulated in
IA32_QM_CTR can be converted to total bandwidth (in bytes) using CPUID.(EAX=0FH, ECX=1H).EBX.
Table 17-19. Monitoring Supported Event IDs
Event Type
Event ID
Context
L3 Cache Occupancy
01H
Cache Monitoring Technology
L3 Total External Bandwidth
02H
MBM
L3 Local External Bandwidth
03H
MBM
Reserved
All other event codes
N/A
17.16.6
Monitoring Resource RMID Association
After Monitoring and sub-features has been enumerated, software can begin using the monitoring features. The
first step is to associate a given software thread (or multiple threads as part of an application, VM, group of applications or other abstraction) with an RMID.
Note that the process of associating an RMID with a given software thread is the same for all shared resource monitoring features (CMT, MBM), and a given RMID number has the same meaning from the viewpoint of any logical
processors in a package. Stated another way, a thread may be associated in a 1:1 mapping with an RMID, and that
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RMID may allow cache occupancy, memory bandwidth information or other monitoring data to be read back later
with monitoring event codes (retrieving data is discussed in a previous section).
The association of an application thread with an RMID requires an OS to program the per-logical-processor MSR
IA32_PQR_ASSOC at context swap time (updates may also be made at any other arbitrary points during program
execution such as application phase changes). The IA32_PQR_ASSOC MSR specifies the active RMID that monitoring hardware will use to tag internal operations, such as L3 cache requests. The layout of the MSR is shown in
Figure 17-23. Software specifies the active RMID to monitor in the IA32_PQR_ASSOC.RMID field. The width of the
RMID field can vary from one implementation to another, and is derived from Ceil (LOG2 ( 1 + CPUID.(EAX=0FH,
ECX=0):EBX[31:0])). The value of IA32_PQR_ASSOC after power-on is 0.
Width of IA32_PQR_ASSOC.RMID field: Log2 ( CPUID.(EAX=0FH, ECX=0H).EBX[31:0] +1)
32 31
63
Reserved for CLOS*
0
10 9
Reserved
RMID
IA32_PQR_ASSOC
*See Section 17.15
Figure 17-23. IA32_PQR_ASSOC MSR
In the initial implementation, the width of the RMID field is up to 10 bits wide, zero-referenced and fully encoded.
However, software must use CPUID to query the maximum RMID supported by the processor. If a value larger than
the maximum RMID is written to IA32_PQR_ASSOC.RMID, a #GP(0) fault will be generated.
RMIDs have a global scope within the physical package- if an RMID is assigned to one logical processor then the
same RMID can be used to read multiple thread attributes later (for example, L3 cache occupancy or external
bandwidth from the L3 to the next level of the cache hierarchy). In a multiple LLC platform the RMIDs are to be
reassigned by the OS or VMM scheduler when an application is migrated across LLCs.
Note that in a situation where Monitoring supports multiple resource types, some upper range of RMIDs (e.g. RMID
31) may only be supported by one resource type but not by another resource type.
17.16.7
Monitoring Resource Selection and Reporting Infrastructure
The reporting mechanism for Cache Monitoring Technology and other related features is architecturally exposed as
an MSR pair that can be programmed and read to measure various metrics such as the L3 cache occupancy (CMT)
and bandwidths (MBM) depending on the level of Monitoring support provided by the platform. Data is reported
back on a per-RMID basis. These events do not trigger based on event counts or trigger APIC interrupts (e.g. no
Performance Monitoring Interrupt occurs based on counts). Rather, they are used to sample counts explicitly.
The MSR pair for the shared resource monitoring features (CMT, MBM) is separate from and not shared with architectural Perfmon counters, meaning software can use these monitoring features simultaneously with the Perfmon
counters.
Access to the aggregated monitoring information is accomplished through the following programmable monitoring
MSRs:
•
IA32_QM_EVTSEL: This MSR provides a role similar to the event select MSRs for programmable performance
monitoring described in Chapter 18. The simplified layout of the MSR is shown in Figure 17-24. Bits
IA32_QM_EVTSEL.EvtID (bits 7:0) specify an event code of a supported resource type for hardware to report
monitored data associated with IA32_QM_EVTSEL.RMID (bits 41:32). Software can configure
IA32_QM_EVTSEL.RMID with any RMID that is active within the physical processor. The width of
IA32_QM_EVTSEL.RMID matches that of IA32_PQR_ASSOC.RMID. Supported event codes for the
IA32_QM_EVTSEL register are shown in Table 17-19. Note that valid event codes may not necessarily map
directly to the bit position used to enumerate support for the resource via CPUID.
Software can program an RMID / Event ID pair into the IA32_QM_EVTSEL MSR bit field to select an RMID to
read a particular counter for a given resource. The currently supported list of Monitoring Event IDs is discussed
in Section 17.16.5, which covers feature-specific details.
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
Thread access to the IA32_QM_EVTSEL and IA32_QM_CTR MSR pair should be serialized to avoid situations
where one thread changes the RMID/EvtID just before another thread reads monitoring data from
IA32_QM_CTR.
•
IA32_QM_CTR: This MSR reports monitored data when available. It contains three bit fields. If software
configures an unsupported RMID or event type in IA32_QM_EVTSEL, then IA32_QM_CTR.Error (bit 63) will be
set, indicating there is no valid data to report. If IA32_QM_CTR.Unavailable (bit 62) is set, it indicates
monitored data for the RMID is not available, and IA32_QM_CTR.data (bits 61:0) should be ignored. Therefore,
IA32_QM_CTR.data (bits 61:0) is valid only if bit 63 and 62 are both clear. For Cache Monitoring Technology,
software can convert IA32_QM_CTR.data into cache occupancy or bandwidth metrics expressed in bytes by
multiplying with the conversion factor from CPUID.(EAX=0FH, ECX=1H).EBX.
42 41
63
Reserved
32 31
8 7
Reserved
RMID
61
63
0
IA32_QM_EVTSEL
EvtID
0
E U
IA32_QM_CTR
Resource Monitoring Data
Figure 17-24. IA32_QM_EVTSEL and IA32_QM_CTR MSRs
17.16.8
Monitoring Programming Considerations
Figure 17-23 illustrates how system software can program IA32_QOSEVTSEL and IA32_QM_CTR to perform
resource monitoring.
System Software
RMID
Event ID
63
Reserved
32
41
RMID
7
Reserved
Counter Data
IA32_QM_CTR MSR
IA32_QOSEVTSEL MSR
63 62
0
Event ID
Resource Monitoring ID
0
Monitoring Data
EvtID
Availability
Error
Figure 17-25. Software Usage of Cache Monitoring Resources
Though the field provided in IA32_QM_CTR allows for up to 62 bits of data to be returned, often a subset of bits are
used. With Cache Monitoring Technology for instance, the number of bits used will be proportional to the base-two
logarithm of the total cache size divided by the Upscaling Factor from CPUID.
In Memory Bandwidth Monitoring the initial counter size is 24 bits, and retrieving the value at 1Hz or faster is sufficient to ensure at most one rollover per sampling period. Any future changes to counter width will be enumerated
to software.
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17.16.8.1 Monitoring Dynamic Configuration
Both the IA32_QM_EVTSEL and IA32_PQR_ASSOC registers are accessible and modifiable at any time during
execution using RDMSR/WRMSR unless otherwise noted. When writing to these MSRs a #GP(0) will be generated
if any of the following conditions occur:
•
•
A reserved bit is modified,
An RMID exceeding the maxRMID is used.
17.16.8.2 Monitoring Operation With Power Saving Features
Note that some advanced power management features such as deep package C-states may shrink the L3 cache
and cause CMT occupancy count to be reduced. MBM bandwidth counts may increase due to flushing cached data
out of L3.
17.16.8.3 Monitoring Operation with Other Operating Modes
The states in IA32_PQR_ASSOC and monitoring counter are unmodified across an SMI delivery. Thus, the execution of SMM handler code and SMM handler’s data can manifest as spurious contribution in the monitored data.
It is possible for an SMM handler to minimize the impact on of spurious contribution in the QOS monitoring counters by reserving a dedicated RMID for monitoring the SMM handler. Such an SMM handler can save the previously
configured QOS Monitoring state immediately upon entering SMM, and restoring the QOS monitoring state back to
the prev-SMM RMID upon exit.
17.16.8.4 Monitoring Operation with RAS Features
In general the Reliability, Availability and Serviceability (RAS) features present in Intel Platforms are not expected
to significantly affect shared resource monitoring counts. In cases where software RAS features cause memory
copies or cache accesses these may be tracked and may influence the shared resource monitoring counter values.
17.17
INTEL® RESOURCE DIRECTOR TECHNOLOGY (INTEL® RDT) ALLOCATION
FEATURES
The Intel Resource Director Technology (Intel RDT) feature set provides a set of allocation (resource control) capabilities including Cache Allocation Technology (CAT) and Code and Data Prioritization (CDP). The Intel Xeon
processor E5 v4 family (and subset of communication-focused Intel Xeon processors E5 v3 family) introduce capabilities to configure and make use of the Cache Allocation Technology (CAT) mechanisms on the L3 cache. Some
future Intel platforms may also provide support for control over the L2 cache, with capabilities as described below.
The programming interface for Cache Allocation Technology and for the more general allocation capabilities are
described in the rest of this chapter.
Cache Allocation Technology enables an Operating System (OS), Hypervisor /Virtual Machine Manager (VMM) or
similar system service management agent to specify the amount of cache space into which an application can fill
(as a hint to hardware - certain features such as power management may override CAT settings). Specialized userlevel implementations with minimal OS support are also possible, though not necessarily recommended (see notes
below for OS/Hypervisor with respect to ring 3 software and virtual guests). Depending on the processor famility,
L2 or L3 cache allocation capability may be provided, and the technology is designed to scale across multiple cache
levels and technology generations.
Software can determine which levels are supported in a give platform programmatically using CPUID as described
in the following sections.
The CAT mechanisms defined in this document provide the following key features:
•
A mechanism to enumerate platform Cache Allocation Technology capabilities and available resource types that
provides CAT control capabilities. For implementations that support Cache Allocation Technology, CPUID
provides enumeration support to query which levels of the cache hierarchy are supported and specific CAT
capabilities, such as the max allocation bitmask size,
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
•
A mechanism for the OS or Hypervisor to configure the amount of a resource available to a particular Class of
Service via a list of allocation bitmasks,
•
•
Mechanisms for the OS or Hypervisor to signal the Class of Service to which an application belongs, and
Hardware mechanisms to guide the LLC fill policy when an application has been designated to belong to a
specific Class of Service.
Note that for many usages, an OS or Hypervisor may not want to expose Cache Allocation Technology mechanisms
to Ring3 software or virtualized guests.
The Cache Allocation Technology feature enables more cache resources (i.e. cache space) to be made available for
high priority applications based on guidance from the execution environment as shown in Figure 17-26. The architecture also allows dynamic resource reassignment during runtime to further optimize the performance of the high
priority application with minimal degradation to the low priority app. Additionally, resources can be rebalanced for
system throughput benefit across uses cases of OSes, VMMs, containers and other scenarios by managing the
CPUID and MSR interfaces. This section describes the hardware and software support required in the platform
including what is required of the execution environment (i.e. OS/VMM) to support such resource control. Note that
in Figure 17-26 the L3 Cache is shown as an example resource.
With CAT
Without CAT
Hi Pri App
Lo Pri App
Hi Pri App
Lo Pri App
Core 0
Core 1
Core 0
Core 1
Shared LLC, Low priority got more cache
Shared LLC, High priority got more cache
Figure 17-26. Cache Allocation Technology Allocates More Resource to High Priority Applications
17.17.1
Cache Allocation Technology Architecture
The fundamental goal of Cache Allocation Technology is to enable resource allocation based on application priority
or Class of Service (COS or CLOS). The processor exposes a set of Classes of Service into which applications (or
individual threads) can be assigned. Cache allocation for the respective applications or threads is then restricted
based on the class with which they are associated. Each Class of Service can be configured using capacity bitmasks
(CBMs) which represent capacity and indicate the degree of overlap and isolation between classes. For each logical
processor there is a register exposed (referred to here as the IA32_PQR_ASSOC MSR or PQR) to allow the OS/VMM
to specify a COS when an application, thread or VM is scheduled.
The usage of Classes of Service (COS) are consistent across resources - and a COS may have multiple re-source
control attributes attached, which reduces software overhead at context swap time. Rather than adding new types
of COS tags per resource for instance, the COS management overhead is constant. Cache allocation for the indicated application/thread/VM is then controlled automatically by the hardware based on the class and the bitmask
associated with that class. Bitmasks are configured via the IA32_resourceType_MASK_n MSRs, where
resourceType indicates a resource type (e.g. “L3” for the L3 cache) and n indicates a COS number.
The basic ingredients of Cache Allocation Technology are as follows:
•
An architecturally exposed mechanism using CPUID to indicate whether CAT is supported, and what resource
types are available which can be controlled,
•
For each available resourceType, CPUID also enumerates the total number of Classes of Services and the length
of the capacity bitmasks that can be used to enforce cache allocation to applications on the platform,
•
An architecturally exposed mechanism to allow the execution environment (OS/VMM) to configure the behavior
of different classes of service using the bitmasks available,
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
•
An architecturally exposed mechanism to allow the execution environment (OS/VMM) to assign a COS to an
executing software thread (i.e. associating the active CR3 of a logical processor with the COS in
IA32_PQR_ASSOC),
•
Implementation-dependent mechanisms to indicate which COS is associated with a memory access and to
enforce the cache allocation on a per COS basis.
A capacity bitmask (CBM) provides a hint to the hardware indicating the cache space an application should be
limited to as well as providing an indication of overlap and isolation in the CAT-capable cache from other applications contending for the cache. The bitlength of the capacity mask available generally depends on the configuration
of the cache and is specified in the enumeration process for CAT in CPUID (this may vary between models in a
processor family as well). Similarly, other parameters such as the number of supported COS may vary for each
resource type, and these details can be enumerated via CPUID.
M7
M6
M5
M4
M3
M2
M1
M0
COS0
A
A
A
A
A
A
A
A
COS1
A
A
A
A
A
A
A
A
COS2
A
A
A
A
A
A
A
A
COS3
A
A
A
A
A
A
A
A
M7
M6
A
COS0
M5
A
M4
A
M3
A
COS1
M2
M1
M0
A
A
A
A
A
A
A
A
A
A
COS2
M7
COS1
COS2
COS3
Overlapped Bitmask
A
COS3
COS0
Default Bitmask
M6
A
M5
A
M4
A
M3
M2
M1
M0
A
Isolated Bitmask
A
A
A
A
Figure 17-27. Examples of Cache Capacity Bitmasks
Sample cache capacity bitmasks for a bitlength of 8 are shown in Figure 17-27. Please note that all (and only)
contiguous '1' combinations are allowed (e.g. FFFFH, 0FF0H, 003CH, etc.). Attempts to program a value without
contiguous '1's (including zero) will result in a general protection fault (#GP(0)). It is generally expected that in
way-based implementations, one capacity mask bit corresponds to some number of ways in cache, but the specific
mapping is implementation-dependent. In all cases, a mask bit set to '1' specifies that a particular Class of Service
can allocate into the cache subset represented by that bit. A value of '0' in a mask bit specifies that a Class of
Service cannot allocate into the given cache subset. In general, allocating more cache to a given application is
usually beneficial to its performance.
Figure 17-27 also shows three examples of sets of Cache Capacity Bitmasks. For simplicity these are represented
as 8-bit vectors, though this may vary depending on the implementation and how the mask is mapped to the available cache capacity. The first example shows the default case where all 4 Classes of Service (the total number of
COS are implementation-dependent) have full access to the cache. The second case shows an overlapped case,
which would allow some lower-priority threads share cache space with the highest priority threads. The third case
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
shows various non-overlapped partitioning schemes. As a matter of software policy for extensibility COS0 should
typically be considered and configured as the highest priority COS, followed by COS1, and so on, though there is
no hardware restriction enforcing this mapping. When the system boots all threads are initialized to COS0, which
has full access to the cache by default.
Though the representation of the CBMs looks similar to a way-based mapping they are independent of any specific
enforcement implementation (e.g. way partitioning.) Rather, this is a convenient manner to represent capacity,
overlap and isolation of cache space. For example, executing a POPCNT instruction (population count of set bits) on
the capacity bitmask can provide the fraction of cache space that a class of service can allocate into. In addition to
the fraction, the exact location of the bits also shows whether the class of service overlaps with other classes of
service or is entirely isolated in terms of cache space used.
Enum/Confg
Association
Enforcement
Enumerate
Enforcement
OS Context
Switch
Application
Memory Request
Configure CBM for
each Class of Service
Set Class of Service
in IA32_PQR
Tag with Cache
Class of Service
Config
COS = 2
Mem Request
COS
Transaction
Cache Subsystem
Enforce Mask
Cache Allocation
Set 1
Set 2
COS 0
Capacity bitmask 3
COS 1
Capacity bitmask 3
COS 2
Capacity bitmask 3
COS 3
Capacity bitmask 3
....
Set n
way 1
......
way 16
Figure 17-28. Class of Service and Cache Capacity Bitmasks
Figure 17-28 shows how the Cache Capacity Bitmasks and the per-logical-processor Class of Service are logically
used to enable Cache Allocation Technology. All (and only) contiguous 1's in the CBM are permitted. The length of
CBM may vary from resource to resource or between processor generations and can be enumerated using CPUID.
From the available mask set and based on the goals of the OS/VMM (shared or isolated cache, etc.) bitmasks are
selected and associated with different classes of service. For the available Classes of Service the associated CBMs
can be programmed via the global set of CAT configuration registers (in the case of L3 CAT, via the
IA32_L3_MASK_n MSRs, where “n” is the Class of Service, starting from zero). In all architectural implementations
supporting CPUID it is possible to change the CBMs dynamically, during program execution, unless stated otherwise by Intel.
The currently running application's Class of Service is communicated to the hardware through the per-logicalprocessor PQR MSR (IA32_PQR_ASSOC MSR). When the OS schedules an application thread on a logical processor,
the application thread is associated with a specific COS (i.e. the corresponding COS in the PQR) and all requests to
the CAT-capable resource from that logical processor are tagged with that COS (in other words, the application
thread is configured to belong to a specific COS). The cache subsystem uses this tagged request information to
enforce QoS. The capacity bitmask may be mapped into a way bitmask (or a similar enforcement entity based on
the implementation) at the cache before it is applied to the allocation policy. For example, the capacity bitmask can
be an 8-bit mask and the enforcement may be accomplished using a 16-way bitmask for a cache enforcement
implementation based on way partitioning.
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The following sections describe extensions of CAT such as Code and Data Prioritization (CDP), followed by details
on specific features such as L3 CAT, L3 CDP, and L2 CAT. Depending on the specific processor a mix of features may
be supported, and CPUID provides enumeration capabilities to enable software to detect the set of supported
features.
17.17.2
Code and Data Prioritization (CDP) Technology
Code and Data Prioritization Technology is an extension of CAT. CDP enables isolation and separate prioritization of
code and data fetches to the L3 cache in a software configurable manner, which can enable workload prioritization
and tuning of cache capacity to the characteristics of the workload. CDP extends Cache Allocation Technology (CAT)
by providing separate code and data masks per Class of Service (COS).
By default, CDP is disabled on the processor. If the CAT MSRs are used without enabling CDP, the processor operates in a traditional CAT-only mode. When CDP is enabled,
•
the CAT mask MSRs are re-mapped into interleaved pairs of mask MSRs for data or code fetches (see
Figure 17-29),
•
the range of COS for CAT is re-indexed, with the lower-half of the COS range available for CDP.
Using the CDP feature, virtual isolation between code and data can be configured on the L3 cache if desired, similar
to how some processor cache levels provide separate L1 data and L1 instruction caches.
Like the CAT feature, CDP may be dynamically configured by privileged software at any point during normal system
operation, including dynamically enabling or disabling the feature provided that certain software configuration
requirements are met (see Section 17.17.4).
An example of the operating mode of CDP is shown in Figure 17-29. Shown at the top are traditional CAT usage
models where capacity masks map 1:1 with a COS number to enable control over the cache space which a given
COS (and thus applications, threads or VMs) may occupy. Shown at the bottom are example mask configurations
where CDP is enabled, and each COS number maps 1:2 to two masks, one for code and one for data. This enables
code and data to be either overlapped or isolated to varying degrees either globally or on a per-COS basis,
depending on application and system needs.
Example of CAT-Only Usage - 16 bit Capacity Masks
COS0
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
COS1
0
0
0
0
1
1
1
1
0
0
0
0
0
0
0
0
COS2
0
0
0
0
0
0
0
0
1
1
0
0
0
0
0
0
COS3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
Traditional
CAT
Example of Code/Data Prioritization Usage - 16 bit Capacity Masks
COS0.Data
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
COS0.Code
0
0
0
0
1
1
0
0
0
0
0
0
0
0
0
0
COS1.Data
0
0
0
0
0
0
1
1
1
1
1
0
0
0
0
0
COS1.Code
0
0
0
0
0
0
0
0
0
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
Other COS.Data
Other COS.Code
CAT with
CDP
Figure 17-29. Code and Data Capacity Bitmasks of CDP
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
When CDP is enabled, the existing mask space for CAT-only operation is split. As an example if the system supports
16 CAT-only COS, when CDP is enabled the same MSR interfaces are used, however half of the masks correspond
to code, half correspond to data, and the effective number of COS is reduced by half. Code/Data masks are defined
per-COS and interleaved in the MSR space as described in subsequent sections.
17.17.3
Enabling Cache Allocation Technology Usage Flow
Figure 17-30 illustrates the key steps for OS/VMM to detect support of Cache Allocation Technology and enable
priority-based resource allocation for a CAT-capable resource.
On OS/VMM Initialization
CQE Capability
Enumeration
Cache Allocation Configuration
Set COS for scheduled
thread context
Configure CBM
per COS
WRMSR
CPUID[
CPUID.(7,0):EBX.15
CPUID.(10H,0):EBX[31:1]
CPUID.(10H,1):EAX[4:0]
CPUID.(10H,1):EDX[15:0]
CPUID.(10H,1):EBX[
On Context Switch
IA32_L3_QOS_MASK_0
...
WRMSR
IA32_PQR_ASSOC
A32_L3_QOS_MASK_n
Figure 17-30. Cache Allocation Technology Usage Flow
Enumeration and configuration of L2 CAT is similar to L3 CAT, however CPUID details and MSR addresses differ.
Common CLOS are used across the features.
17.17.3.1 Enumeration and Detection Support of Cache Allocation Technology
Software can query processor support of CAT capabilities by executing CPUID instruction with EAX = 07H, ECX =
0H as input. If CPUID.(EAX=07H, ECX=0):EBX.PQE[bit 15] reports 1, the processor supports software control over
shared processor resources. Software must use CPUID leaf 10H to enumerate additional details of available
resource types, classes of services and capability bitmasks. The programming interfaces provided by Cache Allocation Technology include:
•
CPUID leaf function 10H (Cache Allocation Technology Enumeration leaf) and its sub-functions provide
information on available resource types, and CAT capability for each resource type (see Section 17.17.3.2).
•
IA32_L3_MASK_n: A range of MSRs is provided for each resource type, each MSR within that range specifying
a software-configured capacity bitmask for each class of service. For L3 with Cache Allocation support, the CBM
is specified using one of the IA32_L3_QOS_MASK_n MSR, where 'n' corresponds to a number within the
supported range of COS, i.e. the range between 0 and CPUID.(EAX=10H, ECX=ResID):EDX[15:0], inclusive.
See Section 17.17.3.3 for details.
•
IA32_L2_MASK_n: A range of MSRs is provided for L2 Cache Allocation Technology, enabling software control
over the amount of L2 cache available for each CLOS. Similar to L3 CAT, a CBM is specified for each CLOS using
the set of registers, IA32_L2_QOS_MASK_n MSR, where 'n' ranges from zero to the maximum CLOS number
reported for L2 CAT in CPUID. See Section 17.17.3.3 for details.
The L2 mask MSRs are scoped at the same level as the L2 cache (similarly, the L3 mask MSRs are scoped at the
same level as the L3 cache). Software may determine which logical processors share an MSR (for instance local
to a core, or shared across multiple cores) by performing a write to one of these MSRs and noting which logical
threads observe the change. Example flows for a similar method to determine register scope are described in
Section 15.5.2, “System Software Recommendation for Managing CMCI and Machine Check Resources”.
Software may also use CPUID leaf 4 to determine the maximum number of logical processor IDs that may share
a given level of the cache.
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•
IA32_PQR_ASSOC.CLOS: The IA32_PQR_ASSOC MSR provides a COS field that OS/VMM can use to assign a
logical processor to an available COS. The set of COS are common across all allocation features, meaning that
multiple features may be supported in the same processor without additional software COS management
overhead at context swap time. See Section 17.17.3.4 for details.
17.17.3.2 Cache Allocation Technology: Resource Type and Capability Enumeration
CPUID leaf function 10H (Cache Allocation Technology Enumeration leaf) provides two or more sub-functions:
•
CAT Enumeration leaf sub-function 0 enumerates available resource types that support allocation control, i.e.
by executing CPUID with EAX=10H and ECX=0H. Each supported resource type is represented by a bit field in
CPUID.(EAX=10H, ECX=0):EBX[31:1]. The bit position of each set bit corresponds to a Resource ID (ResID),
for instance ResID=1 is used to indicate L3 CAT support, and ResID=2 indicates L2 CAT support. The ResID is
also the sub-leaf index that software must use to query details of the CAT capability of that resource type (see
Figure 17-31).
CPUID.(EAX=10H, ECX=0H) Output: (EAX: Reserved; ECX: Reserved; EDX: Reserved)
3 2 1
L L
2 3
31
EBX
Reserved
0
Figure 17-31. CPUID.(EAX=10H, ECX=0H) Available Resource Type Identification
— EAX[4:0] reports the length of the capacity bitmask length using minus-one notation, i.e. a value of 15
corresponds to the capability bitmask having length of 16 bits. Bits 31:5 of EAX are reserved.
•
Sub-functions of CPUID.EAX=10H with a non-zero ECX input matching a supported ResID enumerate the
specific enforcement details of the corresponding ResID. The capabilities enumerated include the length of the
capacity bitmasks and the number of Classes of Service for a given ResID. Software should query the capability
of each available ResID that supports CAT from a sub-leaf of leaf 10H using the sub-leaf index reported by the
corresponding non-zero bit in CPUID.(EAX=10H, ECX=0):EBX[31:1] in order to obtain additional feature
details.
•
CAT capability for L3 is enumerated by CPUID.(EAX=10H, ECX=1H), see Figure 17-32. The specific CAT
capabilities reported by CPUID.(EAX=10H, ECX=1) are:
CPUID.(EAX=10H, ECX=ResID=1) Output:
5 4
31
EAX
Reserved
0
CBM_LEN
31
EBX
0
Bitmask of Shareable Resource with Other executing entities
31
ECX
2 1
0
Reserved
CDP
16 15
31
EDX
Reserved
0
COS_MAX
Figure 17-32. L3 Cache Allocation Technology and CDP Enumeration
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— CPUID.(EAX=10H, ECX=ResID=1):EAX[4:0] reports the length of the capacity bitmask length using
minus-one notation, i.e. a value of 15 corresponds to the capability bitmask having length of 16 bits. Bits
31:5 of EAX are reserved.
— CPUID.(EAX=10H, ECX=1):EBX[31:0] reports a bit mask. Each set bit within the length of the CBM
indicates the corresponding unit of the L3 allocation may be used by other entities in the platform (e.g. an
integrated graphics engine or hardware units outside the processor core and have direct access to L3). Each
cleared bit within the length of the CBM indicates the corresponding allocation unit can be configured to
implement a priority-based allocation scheme chosen by an OS/VMM without interference with other
hardware agents in the system. Bits outside the length of the CBM are reserved.
— CPUID.(EAX=10H, ECX=1):ECX.CDP[bit 2]: If 1, indicates Code and Data Prioritization Technology is
supported (see Section 17.17.4). Other bits of CPUID.(EAX=10H, ECX=1):ECX are reserved.
— CPUID.(EAX=10H, ECX=1):EDX[15:0] reports the maximum COS supported for the resource (COS are
zero-referenced, meaning a reported value of '15' would indicate 16 total supported COS). Bits 31:16 are
reserved.
•
CAT capability for L2 is enumerated by CPUID.(EAX=10H, ECX=2H), see Figure 17-33. The specific CAT
capabilities reported by CPUID.(EAX=10H, ECX=2) are:
CPUID.(EAX=10H, ECX=ResID=2) Output:
5 4
31
EAX
Reserved
0
CBM_LEN
31
EBX
0
Bitmask of Shareable Resource with Other executing entities
31
ECX
0
Reserved
16 15
31
EDX
Reserved
0
COS_MAX
Figure 17-33. L2 Cache Allocation Technology
— CPUID.(EAX=10H, ECX=ResID=2):EAX[4:0] reports the length of the capacity bitmask length using
minus-one notation, i.e. a value of 15 corresponds to the capability bitmask having length of 16 bits. Bits
31:5 of EAX are reserved.
— CPUID.(EAX=10H, ECX=2):EBX[31:0] reports a bit mask. Each set bit within the length of the CBM
indicates the corresponding unit of the L2 allocation may be used by other entities in the platform. Each
cleared bit within the length of the CBM indicates the corresponding allocation unit can be configured to
implement a priority-based allocation scheme chosen by an OS/VMM without interference with other
hardware agents in the system. Bits outside the length of the CBM are reserved.
— CPUID.(EAX=10H, ECX=2):ECX: reserved.
— CPUID.(EAX=10H, ECX=2):EDX[15:0] reports the maximum COS supported for the resource (COS are
zero-referenced, meaning a reported value of '15' would indicate 16 total supported COS). Bits 31:16 are
reserved.
A note on migration of Classes of Service (COS): Software should minimize migrations of COS across logical
processors (across threads or cores), as a reduction in the performance of the Cache Allocation Technology feature
may result if COS are migrated frequently. This is aligned with the industry-standard practice of minimizing unnecessary thread migrations across processor cores in order to avoid excessive time spent warming up processor
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caches after a migration. In general, for best performance, minimize thread migration and COS migration across
processor logical threads and processor cores.
17.17.3.3 Cache Allocation Technology: Cache Mask Configuration
After determining the length of the capacity bitmasks (CBM) and number of COS supported using CPUID (see
Section 17.17.3.2), each COS needs to be programmed with a CBM to dictate its available cache via a write to the
corresponding IA32_resourceType_MASK_n register, where 'n' corresponds to a number within the supported
range of COS, i.e. the range between 0 and CPUID.(EAX=10H, ECX=ResID):EDX[15:0], inclusive, and
'resourceType' corresponds to a specific resource as enumerated by the set bits of CPUID.(EAX=10H,
ECX=0):EAX[31:1], for instance, ‘L2’ or ‘L3’ cache.
A hierarchy of MSRs is reserved for Cache Allocation Technology registers of the form
IA32_resourceType_MASK_n:
•
from 0C90H through 0D8FH (inclusive), providing support for multiple sub-ranges to support varying resource
types. The first supported resourceType is 'L3', corresponding to the L3 cache in a platform. The MSRs range
from 0C90H through 0D0FH (inclusive), enables support for up to 128 L3 CAT Classes of Service.
31
63
COS
63
0
10 9
32 31
Reserved
IA32_PQR_ASSOC
RMID
Reserved
0
IA32_L3_MASK_0
Bit_Mask
....
63
32 31
Reserved
0
Bit_Mask
IA32_L3_MASK_n
Figure 17-34. IA32_PQR_ASSOC, IA32_L3_MASK_n MSRs
•
Within the same CAT range hierarchy, another set of registers is defined for resourceType 'L2', corresponding
to the L2 cache in a platform, and MSRs IA32_L2_MASK_n are defined for n=[0,63] at addresses 0D10H
through 0D4FH (inclusive).
Figure 17-34 and Figure 17-35 provide an overview of the relevant registers.
63
32 31
Reserved
0
IA32_L2_MASK_0
Bit_Mask
....
63
32 31
Reserved
0
Bit_Mask
IA32_L2_MASK_n
Figure 17-35. IA32_L2_MASK_n MSRs
All CAT configuration registers can be accessed using the standard RDMSR / WRMSR instructions.
Note that once L3 or L2 CAT masks are configured, threads can be grouped into Classes of Service (COS) using the
IA32_PQR_ASSOC MSR as described in Section 17.17.3.4 (Class of Service (COS) to Cache Mask Association:
Common Across Allocation Features)
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17.17.3.4 Class of Service to Cache Mask Association: Common Across Allocation Features
After configuring the available classes of service with the preferred set of capacity bitmasks, the OS/VMM can set
the IA32_PQR_ASSOC.COS of a logical processor to the class of service with the desired CBM when a thread
context switch occurs. This allows the OS/VMM to indicate which class of service an executing thread/VM belongs
within. Each logical processor contains an instance of the IA32_PQR_ASSOC register at MSR location 0C8FH, and
Figure 17-34 shows the bit field layout for this register. Bits[63:32] contain the COS field for each logical processor.
Note that placing the RMID field within the same PQR register enables both RMID and CLOS to be swapped at
context swap time for simultaneous use of monitoring and allocation features with a single register write for efficiency.
When CDP is enabled, Specifying a COS value in IA32_PQR_ASSOC.COS greater than MAX_COS_CDP =(
CPUID.(EAX=10H, ECX=1):EDX[15:0] >> 1) will cause undefined performance impact to code and data fetches.
Note that if the IA32_PQR_ASSOC.COS is never written then the CAT capability defaults to using COS 0, which in
turn is set to the default mask in IA32_L3_MASK_0 - which is all “1”s (on reset). This essentially disables the
enforcement feature by default or for legacy operating systems and software.
See Section 17.17.5, “Cache Allocation Technology Programming Considerations” for important COS programming
considerations including maximum values when using CAT and CDP.
17.17.4
Code and Data Prioritization (CDP): Enumerating and Enabling L3 CDP Technology
CDP is an extension of CAT. The presence of the CDP feature is enumerated via CPUID.(EAX=10H,
ECX=1):ECX.CDP[bit 2] (see Figure 17-32). Most of the CPUID.(EAX=10H, ECX=1) sub-leaf data that applies to
CAT also apply to CDP. However, CPUID.(EAX=10H, ECX=1):EDX.COS_MAX_CAT specifies the maximum COS
applicable to CAT-only operation. For CDP operations, COS_MAX_CDP is equal to (CPUID.(EAX=10H,
ECX=1):EDX.COS_MAX_CAT >>1).
If CPUID.(EAX=10H, ECX=1):ECX.CDP[bit 2] =1, the processor supports CDP and provides a new MSR
IA32_L3_QOS_CFG at address 0C81H. The layout of IA32_L3_QOS_CFG is shown in Figure 17-36. The bit field
definition of IA32_L3_QOS_CFG are:
•
Bit 0: L3 CDP Enable. If set, enables CDP, maps CAT mask MSRs into pairs of Data Mask and Code Mask MSRs.
The maximum allowed value to write into IA32_PQR_ASSOC.COS is COS_MAX_CDP.
•
Bits 63:1: Reserved. Attempts to write to reserved bits result in a #GP(0).
IA32_L3_QOS_CFG
63
3 2 1
0
Reserved
L3 CDP Enable
Figure 17-36. Layout of IA32_L3_QOS_CFG
IA32_L3_QOS_CFG default values are all 0s at RESET, the mask MSRs are all 1s. Hence. all logical processors are
initialized in COS0 allocated with the entire L3 with CDP disabled, until software programs CAT and CDP.
Before enabling or disabling CDP, software should write all 1's to all of the CAT/CDP masks to ensure proper
behavior (e.g., the IA32_L3_QOS_Mask_n set of MSRs). When enabling CDP, software should also ensure that only
COS number which are valid in CDP operation is used, otherwise undefined behavior may result. For instance in a
case with 16 CAT COS, since COS are reduced by half when CDP is enabled, software should ensure that only COS
0-7 are in use before enabling CDP (along with writing 1's to all mask bits before enabling or disabling CDP).
Software should also account for the fact that mask interpretations change when CDP is enabled or disabled,
meaning for instance that a CAT mask for a given COS may become a code mask for a different Class of Service
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when CDP is enabled. In order to simplify this behavior and prevent unintended remapping software should
consider resetting all threads to COS[0] before enabling or disabling CDP.
17.17.4.1 Mapping Between L3 CDP Masks and CAT Masks
When CDP is enabled, the existing CAT mask MSR space is re-mapped to provide a code mask and a data mask per
COS. The re-mapping is shown in
Table 17-20. Re-indexing of COS Numbers and Mapping to CAT/CDP Mask MSRs
Mask MSR
CAT-only Operation
CDP Operation
IA32_L3_QOS_Mask_0
COS0
COS0.Data
IA32_L3_QOS_Mask_1
COS1
COS0.Code
IA32_L3_QOS_Mask_2
COS2
COS1.Data
IA32_L3_QOS_Mask_3
COS3
COS1.Code
IA32_L3_QOS_Mask_4
COS4
COS2.Data
IA32_L3_QOS_Mask_5
COS5
COS2.Code
....
....
....
IA32_L3_QOS_Mask_’2n’
COS’2n’
COS’n’.Data
IA32_L3_QOS_Mask_’2n+1’
COS’2n+1’
COS’n’.Code
One can derive the MSR address for the data mask or code mask for a given COS number ‘n’ by:
•
•
data_mask_address (n) = base + (n <<1), where base is the address of IA32_L3_QOS_MASK_0.
code_mask_address (n) = base + (n <<1) +1.
When CDP is enabled, each COS is mapped 1:2 with mask MSRs, with one mask enabling programmatic control
over data fill location and one mask enabling control over data placement. A variety of overlapped and isolated
mask configurations are possible (see the example in Figure 17-29).
Mask MSR field definitions remain the same. Capacity masks must be formed of contiguous set bits, with a length
of 1 bit or longer and should not exceed the maximum mask length specified in CPUID. As examples, valid masks
on a cache with max bitmask length of 16b (from CPUID) include 0xFFFF, 0xFF00, 0x00FF, 0x00F0, 0x0001,
0x0003 and so on. Maximum valid mask lengths are unchanged whether CDP is enabled or disabled, and writes of
invalid mask values may lead to undefined behavior. Writes to reserved bits will generate #GP(0).
17.17.4.2 L3 CAT: Disabling CDP
Before enabling or disabling CDP, software should write all 1's to all of the CAT/CDP masks to ensure proper
behavior (e.g., the IA32_L3_QOS_Mask_n set of MSRs).
Software should also account for the fact that mask interpretations change when CDP is enabled or disabled,
meaning for instance that a CAT mask for a given COS may become a code mask for a different Class of Service
when CDP is enabled. In order to simplify this behavior and prevent unintended remapping software should
consider resetting all threads to COS[0] before enabling or disabling CDP.
17.17.5
Cache Allocation Technology Programming Considerations
17.17.5.1 Cache Allocation Technology Dynamic Configuration
Both the CAT masks and CQM registers are accessible and modifiable at any time during execution using
RDMSR/WRMSR unless otherwise noted. When writing to these MSRs a #GP(0) will be generated if any of the
following conditions occur:
•
A reserved bit is modified,
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DEBUG, BRANCH PROFILE, TSC, AND RESOURCE MONITORING FEATURES
•
Accessing a QOS mask register outside the supported COS (the max COS number is specified in
CPUID.(EAX=10H, ECX=ResID):EDX[15:0]), or
•
Writing a COS greater than the supported maximum (specified as the maximum value of CPUID.(EAX=10H,
ECX=ResID):EDX[15:0] for all valid ResID values) is written to the IA32_PQR_ASSOC.CLOS field.
When CDP is enabled, specifying a COS value in IA32_PQR_ASSOC.COS outside of the lower half of the COS space
will cause undefined performance impact to code and data fetches due to MSR space re-indexing into code/data
masks when CDP is enabled.
When reading the IA32_PQR_ASSOC register the currently programmed COS on the core will be returned.
When reading an IA32_resourceType_MASK_n register the current capacity bit mask for COS 'n' will be returned.
As noted previously, software should minimize migrations of COS across logical processors (across threads or
cores), as a reduction in the accuracy of the Cache Allocation feature may result if COS are migrated frequently.
This is aligned with the industry standard practice of minimizing unnecessary thread migrations across processor
cores in order to avoid excessive time spent warming up processor caches after a migration. In general, for best
performance, minimize thread migration and COS migration across processor logical threads and processor cores.
17.17.5.2 Cache Allocation Technology Operation With Power Saving Features
Note that the Cache Allocation Technology feature cannot be used to enforce cache coherency, and that some
advanced power management features such as C-states which may shrink or power off various caches within the
system may interfere with CAT hints - in such cases the CAT bitmasks are ignored and the other features take
precedence. If the highest possible level of CAT differentiation or determinism is required, disable any powersaving features which shrink the caches or power off caches. The details of the power management interfaces are
typically implementation-specific, but can be found at Intel® 64 and IA-32 Architectures Software Developer’s
Manual, Volume 3C.
If software requires differentiation between threads but not absolute determinism then in many cases it is possible
to leave power-saving cache shrink features enabled, which can provide substantial power savings and increase
battery life in mobile platforms. In such cases when the caches are powered off (e.g., package C-states) the entire
cache of a portion thereof may be powered off. Upon resuming an active state any new incoming data to the cache
will be filled subject to the cache capacity bitmasks. Any data in the cache prior to the cache shrink or power off
may have been flushed to memory during the process of entering the idle state, however, and is not guaranteed to
remain in the cache. If differentiation between threads is the goal of system software then this model allows
substantial power savings while continuing to deliver performance differentiation. If system software needs
optimal determinism then power saving modes which flush portions of the caches and power them off should be
disabled.
NOTE
IA32_PQR_ASSOC is saved and restored across C6 entry/exit. Similarly, the mask register contents
are saved across package C-state entry/exit and are not lost.
17.17.5.3 Cache Allocation Technology Operation with Other Operating Modes
The states in IA32_PQR_ASSOC and mask registers are unmodified across an SMI delivery. Thus, the execution of
SMM handler code can interact with the Cache Allocation Technology resource and manifest some degree of nondeterminism to the non-SMM software stack. An SMM handler may also perform certain system-level or power
management practices that affect CAT operation.
It is possible for an SMM handler to minimize the impact on data determinism in the cache by reserving a COS with
a dedicated partition in the cache. Such an SMM handler can switch to the dedicated COS immediately upon
entering SMM, and switching back to the previously running COS upon exit.
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17.17.5.4 Associating Threads with CAT/CDP Classes of Service
Threads are associated with Classes of Service (CLOS) via the per-logical-processor IA32_PQR_ASSOC MSR. The
same COS concept applies to both CAT and CDP (for instance, COS[5] means the same thing whether CAT or CDP
is in use, and the COS has associated resource usage constraint attributes including cache capacity masks). The
mapping of COS to mask MSRs does change when CDP is enabled, according to the following guidelines:
•
In CAT-only Mode - one set of bitmasks in one mask MSR control both code and data.
— Each COS number map 1:1 with a capacity mask on the applicable resource (e.g., L3 cache).
•
When CDP is enabled,
— Two mask sets exist for each COS number, one for code, one for data.
— Masks for code/data are interleaved in the MSR address space (see Table 17-20).
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17-62 Vol. 3B
CHAPTER 18
PERFORMANCE MONITORING
Intel 64 and IA-32 architectures provide facilities for monitoring performance via a PMU (Performance Monitoring
Unit).
18.1
PERFORMANCE MONITORING OVERVIEW
Performance monitoring was introduced in the Pentium processor with a set of model-specific performance-monitoring counter MSRs. These counters permit selection of processor performance parameters to be monitored and
measured. The information obtained from these counters can be used for tuning system and compiler performance.
In Intel P6 family of processors, the performance monitoring mechanism was enhanced to permit a wider selection
of events to be monitored and to allow greater control events to be monitored. Next, Intel processors based on
Intel NetBurst microarchitecture introduced a distributed style of performance monitoring mechanism and performance events.
The performance monitoring mechanisms and performance events defined for the Pentium, P6 family, and Intel
processors based on Intel NetBurst microarchitecture are not architectural. They are all model specific (not
compatible among processor families). Intel Core Solo and Intel Core Duo processors support a set of architectural
performance events and a set of non-architectural performance events. Newer Intel processor generations support
enhanced architectural performance events and non-architectural performance events.
Starting with Intel Core Solo and Intel Core Duo processors, there are two classes of performance monitoring capabilities. The first class supports events for monitoring performance using counting or interrupt-based event
sampling usage. These events are non-architectural and vary from one processor model to another. They are
similar to those available in Pentium M processors. These non-architectural performance monitoring events are
specific to the microarchitecture and may change with enhancements. They are discussed in Section 18.3, “Performance Monitoring (Intel® Core™ Solo and Intel® Core™ Duo Processors).” Non-architectural events for a given
microarchitecture can not be enumerated using CPUID; and they are listed in Chapter 19, “PerformanceMonitoring Events.”
The second class of performance monitoring capabilities is referred to as architectural performance monitoring.
This class supports the same counting and Interrupt-based event sampling usages, with a smaller set of available
events. The visible behavior of architectural performance events is consistent across processor implementations.
Availability of architectural performance monitoring capabilities is enumerated using the CPUID.0AH. These events
are discussed in Section 18.2.
See also:
— Section 18.2, “Architectural Performance Monitoring”
— Section 18.3, “Performance Monitoring (Intel® Core™ Solo and Intel® Core™ Duo Processors)”
— Section 18.4, “Performance Monitoring (Processors Based on Intel® Core™ Microarchitecture)”
— Section 18.5, “Performance Monitoring (45 nm and 32 nm Intel® Atom™ Processors)”
— Section 18.6, “Performance Monitoring for Silvermont Microarchitecture”
— Section 18.7, “Performance Monitoring for Goldmont Microarchitecture”
— Section 18.8, “Performance Monitoring for Processors Based on Intel® Microarchitecture Code Name
Nehalem”
— Section 18.8.4, “Performance Monitoring for Processors Based on Intel® Microarchitecture Code Name
Westmere”
— Section 18.9, “Performance Monitoring for Processors Based on Intel® Microarchitecture Code Name Sandy
Bridge”
— Section 18.9.8, “Intel® Xeon® Processor E5 Family Uncore Performance Monitoring Facility”
Vol. 3B 18-1
PERFORMANCE MONITORING
— Section 18.10, “3rd Generation Intel® Core™ Processor Performance Monitoring Facility”
— Section 18.11, “4th Generation Intel® Core™ Processor Performance Monitoring Facility”
— Section 18.12, “Intel® Core™ M Processor Performance Monitoring Facility”
— Section 18.13, “6th Generation Intel® Core™ Processor Performance Monitoring Facility”
— Section 18.14, “Performance Monitoring (Processors Based on Intel NetBurst® Microarchitecture)”
— Section 18.15, “Performance Monitoring and Intel Hyper-Threading Technology in Processors Based on Intel
NetBurst® Microarchitecture”
— Section 18.18, “Performance Monitoring and Dual-Core Technology”
— Section 18.19, “Performance Monitoring on 64-bit Intel Xeon Processor MP with Up to 8-MByte L3 Cache”
— Section 18.21, “Performance Monitoring (P6 Family Processor)”
— Section 18.22, “Performance Monitoring (Pentium Processors)”
18.2
ARCHITECTURAL PERFORMANCE MONITORING
Performance monitoring events are architectural when they behave consistently across microarchitectures. Intel
Core Solo and Intel Core Duo processors introduced architectural performance monitoring. The feature provides a
mechanism for software to enumerate performance events and provides configuration and counting facilities for
events.
Architectural performance monitoring does allow for enhancement across processor implementations. The
CPUID.0AH leaf provides version ID for each enhancement. Intel Core Solo and Intel Core Duo processors support
base level functionality identified by version ID of 1. Processors based on Intel Core microarchitecture support, at
a minimum, the base level functionality of architectural performance monitoring. Intel Core 2 Duo processor T
7700 and newer processors based on Intel Core microarchitecture support both the base level functionality and
enhanced architectural performance monitoring identified by version ID of 2.
45 nm and 32 nm Intel Atom processors and Intel Atom processors based on the Silvermont microarchitecture
support the functionality provided by versionID 1, 2, and 3; CPUID.0AH:EAX[7:0] reports versionID = 3 to indicate
the aggregate of architectural performance monitoring capabilities. Intel Atom processors based on the Airmont
microarchitecture support the same performance monitoring capabilities as those based on the Silvermont microarchitecture.
Intel Core processors and related Intel Xeon processor families based on the Nehalem through Broadwell microarchitectures support version ID 1, 2, and 3. Intel processors based on the Skylake microarchitecture support
versionID 4.
Next generation Intel Atom processors is based on the Goldmont microarchitecture. Intel processors based on the
Goldmont microarchitecture support versionID 4.
18.2.1
Architectural Performance Monitoring Version 1
Configuring an architectural performance monitoring event involves programming performance event select registers. There are a finite number of performance event select MSRs (IA32_PERFEVTSELx MSRs). The result of a
performance monitoring event is reported in a performance monitoring counter (IA32_PMCx MSR). Performance
monitoring counters are paired with performance monitoring select registers.
Performance monitoring select registers and counters are architectural in the following respects:
•
•
•
•
Bit field layout of IA32_PERFEVTSELx is consistent across microarchitectures.
Addresses of IA32_PERFEVTSELx MSRs remain the same across microarchitectures.
Addresses of IA32_PMC MSRs remain the same across microarchitectures.
Each logical processor has its own set of IA32_PERFEVTSELx and IA32_PMCx MSRs. Configuration facilities and
counters are not shared between logical processors sharing a processor core.
Architectural performance monitoring provides a CPUID mechanism for enumerating the following information:
18-2 Vol. 3B
PERFORMANCE MONITORING
•
Number of performance monitoring counters available in a logical processor (each IA32_PERFEVTSELx MSR is
paired to the corresponding IA32_PMCx MSR)
•
•
Number of bits supported in each IA32_PMCx
Number of architectural performance monitoring events supported in a logical processor
Software can use CPUID to discover architectural performance monitoring availability (CPUID.0AH). The architectural performance monitoring leaf provides an identifier corresponding to the version number of architectural
performance monitoring available in the processor.
The version identifier is retrieved by querying CPUID.0AH:EAX[bits 7:0] (see Chapter 3, “Instruction Set Reference, A-M,” in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 2A). If the version
identifier is greater than zero, architectural performance monitoring capability is supported. Software queries the
CPUID.0AH for the version identifier first; it then analyzes the value returned in CPUID.0AH.EAX, CPUID.0AH.EBX
to determine the facilities available.
In the initial implementation of architectural performance monitoring; software can determine how many
IA32_PERFEVTSELx/ IA32_PMCx MSR pairs are supported per core, the bit-width of PMC, and the number of architectural performance monitoring events available.
18.2.1.1
Architectural Performance Monitoring Version 1 Facilities
Architectural performance monitoring facilities include a set of performance monitoring counters and performance
event select registers. These MSRs have the following properties:
•
IA32_PMCx MSRs start at address 0C1H and occupy a contiguous block of MSR address space; the number of
MSRs per logical processor is reported using CPUID.0AH:EAX[15:8].
•
IA32_PERFEVTSELx MSRs start at address 186H and occupy a contiguous block of MSR address space. Each
performance event select register is paired with a corresponding performance counter in the 0C1H address
block.
•
The bit width of an IA32_PMCx MSR is reported using the CPUID.0AH:EAX[23:16]. This the number of valid bits
for read operation. On write operations, the lower-order 32 bits of the MSR may be written with any value, and
the high-order bits are sign-extended from the value of bit 31.
•
Bit field layout of IA32_PERFEVTSELx MSRs is defined architecturally.
See Figure 18-1 for the bit field layout of IA32_PERFEVTSELx MSRs. The bit fields are:
•
Event select field (bits 0 through 7) — Selects the event logic unit used to detect microarchitectural
conditions (see Table 18-1, for a list of architectural events and their 8-bit codes). The set of values for this field
is defined architecturally; each value corresponds to an event logic unit for use with an architectural
performance event. The number of architectural events is queried using CPUID.0AH:EAX. A processor may
support only a subset of pre-defined values.
63
31
24 23 22 21 20 19 18 17 16 15
Counter Mask I E
N
(CMASK)
V N
INV—Invert counter mask
EN—Enable counters
INT—APIC interrupt enable
PC—Pin control
E—Edge detect
OS—Operating system mode
USR—User Mode
0
8 7
I
U
N P E O S Unit Mask (UMASK)
S R
T C
Event Select
Reserved
Figure 18-1. Layout of IA32_PERFEVTSELx MSRs
Vol. 3B 18-3
PERFORMANCE MONITORING
•
Unit mask (UMASK) field (bits 8 through 15) — These bits qualify the condition that the selected event
logic unit detects. Valid UMASK values for each event logic unit are specific to the unit. For each architectural
performance event, its corresponding UMASK value defines a specific microarchitectural condition.
A pre-defined microarchitectural condition associated with an architectural event may not be applicable to a
given processor. The processor then reports only a subset of pre-defined architectural events. Pre-defined
architectural events are listed in Table 18-1; support for pre-defined architectural events is enumerated using
CPUID.0AH:EBX. Architectural performance events available in the initial implementation are listed in Table
19-1.
•
USR (user mode) flag (bit 16) — Specifies that the selected microarchitectural condition is counted when
the logical processor is operating at privilege levels 1, 2 or 3. This flag can be used with the OS flag.
•
OS (operating system mode) flag (bit 17) — Specifies that the selected microarchitectural condition is
counted when the logical processor is operating at privilege level 0. This flag can be used with the USR flag.
•
E (edge detect) flag (bit 18) — Enables (when set) edge detection of the selected microarchitectural
condition. The logical processor counts the number of deasserted to asserted transitions for any condition that
can be expressed by the other fields. The mechanism does not permit back-to-back assertions to be distinguished.
This mechanism allows software to measure not only the fraction of time spent in a particular state, but also the
average length of time spent in such a state (for example, the time spent waiting for an interrupt to be
serviced).
•
PC (pin control) flag (bit 19) — When set, the logical processor toggles the PMi pins and increments the
counter when performance-monitoring events occur; when clear, the processor toggles the PMi pins when the
counter overflows. The toggling of a pin is defined as assertion of the pin for a single bus clock followed by
deassertion.
•
INT (APIC interrupt enable) flag (bit 20) — When set, the logical processor generates an exception
through its local APIC on counter overflow.
•
EN (Enable Counters) Flag (bit 22) — When set, performance counting is enabled in the corresponding
performance-monitoring counter; when clear, the corresponding counter is disabled. The event logic unit for a
UMASK must be disabled by setting IA32_PERFEVTSELx[bit 22] = 0, before writing to IA32_PMCx.
•
INV (invert) flag (bit 23) — When set, inverts the counter-mask (CMASK) comparison, so that both greater
than or equal to and less than comparisons can be made (0: greater than or equal; 1: less than). Note if
counter-mask is programmed to zero, INV flag is ignored.
•
Counter mask (CMASK) field (bits 24 through 31) — When this field is not zero, a logical processor
compares this mask to the events count of the detected microarchitectural condition during a single cycle. If
the event count is greater than or equal to this mask, the counter is incremented by one. Otherwise the counter
is not incremented.
This mask is intended for software to characterize microarchitectural conditions that can count multiple
occurrences per cycle (for example, two or more instructions retired per clock; or bus queue occupations). If
the counter-mask field is 0, then the counter is incremented each cycle by the event count associated with
multiple occurrences.
18.2.1.2
Pre-defined Architectural Performance Events
Table 18-1 lists architecturally defined events.
Table 18-1. UMask and Event Select Encodings for Pre-Defined Architectural Performance Events
Bit Position
CPUID.AH.EBX
Event Name
UMask
Event Select
0
UnHalted Core Cycles
00H
3CH
1
Instruction Retired
00H
C0H
2
UnHalted Reference Cycles
01H
3CH
3
LLC Reference
4FH
2EH
4
LLC Misses
41H
2EH
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PERFORMANCE MONITORING
Table 18-1. UMask and Event Select Encodings for Pre-Defined Architectural Performance Events
5
Branch Instruction Retired
00H
C4H
6
Branch Misses Retired
00H
C5H
A processor that supports architectural performance monitoring may not support all the predefined architectural
performance events (Table 18-1). The non-zero bits in CPUID.0AH:EBX indicate the events that are not available.
The behavior of each architectural performance event is expected to be consistent on all processors that support
that event. Minor variations between microarchitectures are noted below:
•
UnHalted Core Cycles — Event select 3CH, Umask 00H
This event counts core clock cycles when the clock signal on a specific core is running (not halted). The counter
does not advance in the following conditions:
— an ACPI C-state other than C0 for normal operation
— HLT
— STPCLK# pin asserted
— being throttled by TM1
— during the frequency switching phase of a performance state transition (see Chapter 14, “Power and
Thermal Management”)
The performance counter for this event counts across performance state transitions using different core clock
frequencies
•
Instructions Retired — Event select C0H, Umask 00H
This event counts the number of instructions at retirement. For instructions that consist of multiple micro-ops,
this event counts the retirement of the last micro-op of the instruction. An instruction with a REP prefix counts
as one instruction (not per iteration). Faults before the retirement of the last micro-op of a multi-ops instruction
are not counted.
This event does not increment under VM-exit conditions. Counters continue counting during hardware
interrupts, traps, and inside interrupt handlers.
•
UnHalted Reference Cycles — Event select 3CH, Umask 01H
This event counts reference clock cycles while the clock signal on the core is running. The reference clock
operates at a fixed frequency, irrespective of core frequency changes due to performance state transitions.
Processors may implement this behavior differently. See Table 19-23 and Table 19-27 in Chapter 19, “Performance-Monitoring Events.”
•
Last Level Cache References — Event select 2EH, Umask 4FH
This event counts requests originating from the core that reference a cache line in the last level cache. The
event count includes speculation and cache line fills due to the first-level cache hardware prefetcher, but may
exclude cache line fills due to other hardware-prefetchers.
Because cache hierarchy, cache sizes and other implementation-specific characteristics; value comparison to
estimate performance differences is not recommended.
•
Last Level Cache Misses — Event select 2EH, Umask 41H
This event counts each cache miss condition for references to the last level cache. The event count may include
speculation and cache line fills due to the first-level cache hardware prefetcher, but may exclude cache line fills
due to other hardware-prefetchers.
Because cache hierarchy, cache sizes and other implementation-specific characteristics; value comparison to
estimate performance differences is not recommended.
•
Branch Instructions Retired — Event select C4H, Umask 00H
This event counts branch instructions at retirement. It counts the retirement of the last micro-op of a branch
instruction.
•
All Branch Mispredict Retired — Event select C5H, Umask 00H
Vol. 3B 18-5
PERFORMANCE MONITORING
This event counts mispredicted branch instructions at retirement. It counts the retirement of the last micro-op
of a branch instruction in the architectural path of execution and experienced misprediction in the branch
prediction hardware.
Branch prediction hardware is implementation-specific across microarchitectures; value comparison to
estimate performance differences is not recommended.
NOTE
Programming decisions or software precisians on functionality should not be based on the event
values or dependent on the existence of performance monitoring events.
18.2.2
Architectural Performance Monitoring Version 2
The enhanced features provided by architectural performance monitoring version 2 include the following:
•
Fixed-function performance counter register and associated control register — Three of the architectural performance events are counted using three fixed-function MSRs (IA32_FIXED_CTR0 through
IA32_FIXED_CTR2). Each of the fixed-function PMC can count only one architectural performance event.
Configuring the fixed-function PMCs is done by writing to bit fields in the MSR (IA32_FIXED_CTR_CTRL) located
at address 38DH. Unlike configuring performance events for general-purpose PMCs (IA32_PMCx) via UMASK
field in (IA32_PERFEVTSELx), configuring, programming IA32_FIXED_CTR_CTRL for fixed-function PMCs do
not require any UMASK.
•
Simplified event programming — Most frequent operation in programming performance events are
enabling/disabling event counting and checking the status of counter overflows. Architectural performance
event version 2 provides three architectural MSRs:
— IA32_PERF_GLOBAL_CTRL allows software to enable/disable event counting of all or any combination of
fixed-function PMCs (IA32_FIXED_CTRx) or any general-purpose PMCs via a single WRMSR.
— IA32_PERF_GLOBAL_STATUS allows software to query counter overflow conditions on any combination of
fixed-function PMCs or general-purpose PMCs via a single RDMSR.
— IA32_PERF_GLOBAL_OVF_CTRL allows software to clear counter overflow conditions on any combination of
fixed-function PMCs or general-purpose PMCs via a single WRMSR.
•
PMI Overhead Mitigation — Architectural performance monitoring version 2 introduces two bit field interface
in IA32_DEBUGCTL for PMI service routine to accumulate performance monitoring data and LBR records with
reduced perturbation from servicing the PMI. The two bit fields are:
— IA32_DEBUGCTL.Freeze_LBR_On_PMI(bit 11). In architectural performance monitoring version 2, only the
legacy semantic behavior is supported. See Section 17.4.7 for details of the legacy Freeze LBRs on PMI
control.
— IA32_DEBUGCTL.Freeze_PerfMon_On_PMI(bit 12). In architectural performance monitoring version 2, only
the legacy semantic behavior is supported. See Section 17.4.7 for details of the legacy Freeze LBRs on PMI
control.
The facilities provided by architectural performance monitoring version 2 can be queried from CPUID leaf 0AH by
examining the content of register EDX:
•
Bits 0 through 4 of CPUID.0AH.EDX indicates the number of fixed-function performance counters available per
core,
•
Bits 5 through 12 of CPUID.0AH.EDX indicates the bit-width of fixed-function performance counters. Bits
beyond the width of the fixed-function counter are reserved and must be written as zeros.
NOTE
Early generation of processors based on Intel Core microarchitecture may report in
CPUID.0AH:EDX of support for version 2 but indicating incorrect information of version 2 facilities.
The IA32_FIXED_CTR_CTRL MSR include multiple sets of 4-bit field, each 4 bit field controls the operation of a
fixed-function performance counter. Figure 18-2 shows the layout of 4-bit controls for each fixed-function PMC.
Two sub-fields are currently defined within each control. The definitions of the bit fields are:
18-6 Vol. 3B
PERFORMANCE MONITORING
63
12 11
9 8 7
P
M
I
P
M
I
E
N
5 43 2 1 0
E
N
P
M
I
E
N
Cntr2 — Controls for IA32_FIXED_CTR2
Cntr1 — Controls for IA32_FIXED_CTR1
PMI — Enable PMI on overflow
Cntr0 — Controls for IA32_FIXED_CTR0
ENABLE — 0: disable; 1: OS; 2: User; 3: All ring levels
Reserved
Figure 18-2. Layout of IA32_FIXED_CTR_CTRL MSR
•
Enable field (lowest 2 bits within each 4-bit control) — When bit 0 is set, performance counting is
enabled in the corresponding fixed-function performance counter to increment while the target condition
associated with the architecture performance event occurred at ring 0. When bit 1 is set, performance counting
is enabled in the corresponding fixed-function performance counter to increment while the target condition
associated with the architecture performance event occurred at ring greater than 0. Writing 0 to both bits stops
the performance counter. Writing a value of 11B enables the counter to increment irrespective of privilege
levels.
•
PMI field (the fourth bit within each 4-bit control) — When set, the logical processor generates an
exception through its local APIC on overflow condition of the respective fixed-function counter.
IA32_PERF_GLOBAL_CTRL MSR provides single-bit controls to enable counting of each performance counter.
Figure 18-3 shows the layout of IA32_PERF_GLOBAL_CTRL. Each enable bit in IA32_PERF_GLOBAL_CTRL is
AND’ed with the enable bits for all privilege levels in the respective IA32_PERFEVTSELx or
IA32_PERF_FIXED_CTR_CTRL MSRs to start/stop the counting of respective counters. Counting is enabled if the
AND’ed results is true; counting is disabled when the result is false.
63
35 34 33 32 31
2 1 0
IA32_FIXED_CTR2 enable
IA32_FIXED_CTR1 enable
IA32_FIXED_CTR0 enable
IA32_PMC1 enable
IA32_PMC0 enable
Reserved
Figure 18-3. Layout of IA32_PERF_GLOBAL_CTRL MSR
The fixed-function performance counters supported by architectural performance version 2 is listed in Table 18-8,
the pairing between each fixed-function performance counter to an architectural performance event is also shown.
IA32_PERF_GLOBAL_STATUS MSR provides single-bit status for software to query the overflow condition of each
performance counter. IA32_PERF_GLOBAL_STATUS[bit 62] indicates overflow conditions of the DS area data
buffer. IA32_PERF_GLOBAL_STATUS[bit 63] provides a CondChgd bit to indicate changes to the state of performance monitoring hardware. Figure 18-4 shows the layout of IA32_PERF_GLOBAL_STATUS. A value of 1 in bits 0,
1, 32 through 34 indicates a counter overflow condition has occurred in the associated counter.
Vol. 3B 18-7
PERFORMANCE MONITORING
When a performance counter is configured for PEBS, overflow condition in the counter generates a performancemonitoring interrupt signaling a PEBS event. On a PEBS event, the processor stores data records into the buffer
area (see Section 18.15.5), clears the counter overflow status., and sets the “OvfBuffer” bit in
IA32_PERF_GLOBAL_STATUS.
63 62
35 34 33 32 31
2 1 0
CondChgd
OvfDSBuffer
IA32_FIXED_CTR2 Overflow
IA32_FIXED_CTR1 Overflow
IA32_FIXED_CTR0 Overflow
IA32_PMC1 Overflow
IA32_PMC0 Overflow
Reserved
Figure 18-4. Layout of IA32_PERF_GLOBAL_STATUS MSR
IA32_PERF_GLOBAL_OVF_CTL MSR allows software to clear overflow indicator(s) of any general-purpose or fixedfunction counters via a single WRMSR. Software should clear overflow indications when
•
•
•
Setting up new values in the event select and/or UMASK field for counting or interrupt-based event sampling.
Reloading counter values to continue collecting next sample.
Disabling event counting or interrupt-based event sampling.
The layout of IA32_PERF_GLOBAL_OVF_CTL is shown in Figure 18-5.
63 62
35 34 33 32 31
2 1 0
ClrCondChgd
ClrOvfDSBuffer
IA32_FIXED_CTR2 ClrOverflow
IA32_FIXED_CTR1 ClrOverflow
IA32_FIXED_CTR0 ClrOverflow
IA32_PMC1 ClrOverflow
IA32_PMC0 ClrOverflow
Reserved
Figure 18-5. Layout of IA32_PERF_GLOBAL_OVF_CTRL MSR
18.2.3
Architectural Performance Monitoring Version 3
Processors supporting architectural performance monitoring version 3 also supports version 1 and 2, as well as
capability enumerated by CPUID leaf 0AH. Specifically, version 3 provides the following enhancement in performance monitoring facilities if a processor core comprising of more than one logical processor, i.e. a processor core
supporting Intel Hyper-Threading Technology or simultaneous multi-threading capability:
•
Anythread counting for processor core supporting two or more logical processors. The interface that supports
AnyThread counting include:
— Each IA32_PERFEVTSELx MSR (starting at MSR address 186H) support the bit field layout defined in Figure
18-6.
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PERFORMANCE MONITORING
63
31
24 23 22 21 20 19 18 17 16 15
0
8 7
A I
U
Counter Mask I E N
N
N P E O S Unit Mask (UMASK)
(CMASK)
S R
V N Y T C
INV—Invert counter mask
EN—Enable counters
ANY—Any Thread
INT—APIC interrupt enable
PC—Pin control
E—Edge detect
OS—Operating system mode
USR—User Mode
Event Select
Reserved
Figure 18-6. Layout of IA32_PERFEVTSELx MSRs Supporting Architectural Performance Monitoring Version 3
Bit 21 (AnyThread) of IA32_PERFEVTSELx is supported in architectural performance monitoring version 3 for
processor core comprising of two or more logical processors. When set to 1, it enables counting the associated
event conditions (including matching the thread’s CPL with the OS/USR setting of IA32_PERFEVTSELx)
occurring across all logical processors sharing a processor core. When bit 21 is 0, the counter only increments
the associated event conditions (including matching the thread’s CPL with the OS/USR setting of
IA32_PERFEVTSELx) occurring in the logical processor which programmed the IA32_PERFEVTSELx MSR.
— Each fixed-function performance counter IA32_FIXED_CTRx (starting at MSR address 309H) is configured
by a 4-bit control block in the IA32_PERF_FIXED_CTR_CTRL MSR. The control block also allow threadspecificity configuration using an AnyThread bit. The layout of IA32_PERF_FIXED_CTR_CTRL MSR is
shown.
63
12 11
P A
M N
I Y
9 8 7
E
N
P A
M N
I Y
5 43 2 1 0
E
N
P A
M N
I Y
E
N
Cntr2 — Controls for IA32_FIXED_CTR2
Cntr1 — Controls for IA32_FIXED_CTR1
PMI — Enable PMI on overflow on IA32_FIXED_CTR0
AnyThread — AnyThread for IA32_FIXED_CTR0
ENABLE — IA32_FIXED_CTR0. 0: disable; 1: OS; 2: User; 3: All ring levels
Reserved
Figure 18-7. IA32_FIXED_CTR_CTRL MSR Supporting Architectural Performance Monitoring Version 3
Each control block for a fixed-function performance counter provides a AnyThread (bit position 2 + 4*N, N=
0, 1, etc.) bit. When set to 1, it enables counting the associated event conditions (including matching the
thread’s CPL with the ENABLE setting of the corresponding control block of IA32_PERF_FIXED_CTR_CTRL)
occurring across all logical processors sharing a processor core. When an AnyThread bit is 0 in
IA32_PERF_FIXED_CTR_CTRL, the corresponding fixed counter only increments the associated event
conditions occurring in the logical processor which programmed the IA32_PERF_FIXED_CTR_CTRL MSR.
•
The IA32_PERF_GLOBAL_CTRL, IA32_PERF_GLOBAL_STATUS, IA32_PERF_GLOBAL_OVF_CTRL MSRs provide
single-bit controls/status for each general-purpose and fixed-function performance counter. Figure 18-8 and
Figure 18-9 show the layout of these MSRs for N general-purpose performance counters (where N is reported
by CPUID.0AH:EAX[15:8]) and three fixed-function counters.
Note: The number of general-purpose performance monitoring counters (i.e. N in Figure 18-9) can vary across
processor generations within a processor family, across processor families, or could be different depending on
the configuration chosen at boot time in the BIOS regarding Intel Hyper Threading Technology, (e.g. N=2 for
45 nm Intel Atom processors; N =4 for processors based on the Nehalem microarchitecture; for processors
Vol. 3B 18-9
PERFORMANCE MONITORING
based on the Sandy Bridge microarchitecture, N = 4 if Intel Hyper Threading Technology is active and N=8 if
not active).
Global Enable Controls IA32_PERF_GLOBAL_CTRL
35 34 33 32 31
63
N .. .. 1 0
Reserved
IA32_FIXED_CTR2 enable
IA32_FIXED_CTR1 enable
IA32_FIXED_CTR0 enable
IA32_PMC(N-1) enable
.................... enable
IA32_PMC1 enable
IA32_PMC0 enable
Figure 18-8. Layout of Global Performance Monitoring Control MSR
63 62 61
Global Overflow Status IA32_PERF_GLOBAL_STATUS
35 34 33 32 31
CondChgd
OvfDSBuffer
OvfUncore
IA32_FIXED_CTR2 Overflow
IA32_FIXED_CTR1 Overflow
IA32_FIXED_CTR0 Overflow
IA32_PMC1 Overflow
IA32_PMC0 Overflow
63 62
N .. .. 1 0
IA32_PMC(N-1) Overflow
...................... Overflow
Global Overflow Status IA32_PERF_GLOBAL_OVF_CTRL
35 34 33 32 31
ClrCondChgd
ClrOvfDSBuffer
ClrOvfUncore
IA32_FIXED_CTR2 ClrOverflow
IA32_FIXED_CTR1 ClrOverflow
IA32_FIXED_CTR0 ClrOverflow
IA32_PMC1 ClrOverflow
IA32_PMC0 ClrOverflow
N .. .. 1 0
IA32_PMC(N-1) ClrOverflow
........................ ClrOverflow
Figure 18-9. Global Performance Monitoring Overflow Status and Control MSRs
18.2.3.1
AnyThread Counting and Software Evolution
The motivation for characterizing software workload over multiple software threads running on multiple logical
processors of the same processor core originates from a time earlier than the introduction of the AnyThread interface in IA32_PERFEVTSELx and IA32_FIXED_CTR_CTRL. While Anythread counting provides some benefits in
simple software environments of an earlier era, the evolution contemporary software environments introduce
certain concepts and pre-requisites that AnyThread counting does not comply with.
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PERFORMANCE MONITORING
One example is the proliferation of software environments that support multiple virtual machines (VM) under VMX
(see Chapter 23, “Introduction to Virtual-Machine Extensions”) where each VM represents a domain separated
from one another.
A Virtual Machine Monitor (VMM) that manages the VMs may allow individual VM to employ performance monitoring facilities to profiles the performance characteristics of a workload. The use of the Anythread interface in
IA32_PERFEVTSELx and IA32_FIXED_CTR_CTRL is discouraged with software environments supporting virtualization or requiring domain separation.
Specifically, Intel recommends VMM:
•
configure the MSR bitmap to cause VM-exits for WRMSR to IA32_PERFEVTSELx and IA32_FIXED_CTR_CTRL in
VMX non-Root operation (see CHAPTER 24 for additional information),
•
clear the AnyThread bit of IA32_PERFEVTSELx and IA32_FIXED_CTR_CTRL in the MSR-load lists for VM exits
and VM entries (see CHAPTER 24, CHAPTER 26, and CHAPTER 27).
Even when operating in simpler legacy software environments which might not emphasize the pre-requisites of a
virtualized software environment, the use of the AnyThread interface should be moderated and follow any eventspecific guidance where explicitly noted (see relevant sections of Chapter 19, “Performance Monitoring Events”).
18.2.4
Architectural Performance Monitoring Version 4
Processors supporting architectural performance monitoring version 4 also supports version 1, 2, and 3, as well as
capability enumerated by CPUID leaf 0AH. Version 4 introduced a streamlined PMI overhead mitigation interface
that replaces the legacy semantic behavior but retains the same control interface in
IA32_DEBUGCTL.Freeze_LBRs_On_PMI and Freeze_PerfMon_On_PMI. Specifically version 4 provides the following
enhancement:
•
•
New indicators (LBR_FRZ, CTR_FRZ) in IA32_PERF_GLOBAL_STATUS, see Section 18.2.4.1.
•
Fine-grain separation of control interface to manage overflow/status of IA32_PERF_GLOBAL_STATUS and
read-only performance counter enabling interface in IA32_PERF_GLOBAL_STATUS: see Section 18.2.4.2.
•
Performance monitoring resource in-use MSR to facilitate cooperative sharing protocol between perfmonmanaging privilege agents:
Streamlined Freeze/PMI Overhead management interfaces to use IA32_DEBUGCTL.Freeze_LBRs_On_PMI and
IA32_DEBUGCTL.Freeze_PerfMon_On_PMI: see Section 18.2.4.1. Legacy semantics of Freeze_LBRs_On_PMI
and Freeze_PerfMon_On_PMI (applicable to version 2 and 3) are not supported with version 4 or higher.
18.2.4.1
Enhancement in IA32_PERF_GLOBAL_STATUS
The IA32_PERF_GLOBAL_STATUS MSR provides the following indicators with architectural performance monitoring
version 4:
•
IA32_PERF_GLOBAL_STATUS.LBR_FRZ[bit 58]: This bit is set due to the following conditions:
— IA32_DEBUGCTL.FREEZE_LBR_ON_PMI has been set by the profiling agent, and
— A performance counter, configured to generate PMI, has overflowed to signal a PMI. Consequently the LBR
stack is frozen.
Effectively, the IA32_PERF_GLOBAL_STATUS.LBR_FRZ bit also serve as an read-only control to enable
capturing data in the LBR stack. To enable capturing LBR records, the following expression must hold with
architectural perfmon version 4 or higher:
— (IA32_DEBUGCTL.LBR & (!IA32_PERF_GLOBAL_STATUS.LBR_FRZ) ) =1
•
IA32_PERF_GLOBAL_STATUS.CTR_FRZ[bit 59]: This bit is set due to the following conditions:
— IA32_DEBUGCTL.FREEZE_PERFMON_ON_PMI has been set by the profiling agent, and
— A performance counter, configured to generate PMI, has overflowed to signal a PMI. Consequently, all the
performance counters are frozen.
Vol. 3B 18-11
PERFORMANCE MONITORING
Effectively, the IA32_PERF_GLOBAL_STATUS.CTR_FRZ bit also serve as an read-only control to enable
programmable performance counters and fixed counters in the core PMU. To enable counting with the
performance counters, the following expression must hold with architectural perfmon version 4 or higher:
•
(IA32_PERFEVTSELn.EN & IA32_PERF_GLOBAL_CTRL.PMCn &
(!IA32_PERF_GLOBAL_STATUS.CTR_FRZ) ) = 1 for programmable counter ‘n’, or
•
(IA32_PERF_FIXED_CRTL.ENi & IA32_PERF_GLOBAL_CTRL.FCi &
(!IA32_PERF_GLOBAL_STATUS.CTR_FRZ) ) = 1 for fixed counter ‘i’
The read-only enable interface IA32_PERF_GLOBAL_STATUS.CTR_FRZ provides a more efficient flow for a PMI
handler to use IA32_DEBUGCTL.Freeza_Perfmon_On_PMI to filter out data that may distort target workload analysis, see Table 17-3. It should be noted the IA32_PERF_GLOBAL_CTRL register continue to serve as the primary
interface to control all performance counters of the logical processor.
For example, when the Freeze-On-PMI mode is not being used, a PMI handler would be setting
IA32_PERF_GLOBAL_CTRL as the very last step to commence the overall operation after configuring the individual
counter registers, controls and PEBS facility. This does not only assure atomic monitoring but also avoids unnecessary complications (e.g. race conditions) when software attempts to change the core PMU configuration while some
counters are kept enabled.
Additionally, IA32_PERF_GLOBAL_STATUS.TraceToPAPMI[bit 55]: On processors that support Intel Processor Trace
and configured to store trace output packets to physical memory using the ToPA scheme, bit 55 is set when a PMI
occurred due to a ToPA entry memory buffer was completely filled.
IA32_PERF_GLOBAL_STATUS also provides an indicator to distinguish interaction of performance monitoring operations with other side-band activities, which apply Intel SGX on processors that support SGX (For additional information about Intel SGX, see “Intel® Software Guard Extensions Programming Reference”.):
•
IA32_PERF_GLOBAL_STATUS.ASCI[bit 60]: This bit is set when data accumulated in any of the configured
performance counters (i.e. IA32_PMCx or IA32_FIXED_CTRx) may include contributions from direct or indirect
operation of Intel SGX to protect an enclave (since the last time IA32_PERF_GLOBAL_STATUS.ASCI was
cleared).
63 62 61 60 59 58
CondChgd
OvfDSBuffer
OvfUncore
ASCI
CTR_Frz
LBR_Frz
TraceToPAPMI
IA32_FIXED_CTR2 Overflow
IA32_FIXED_CTR1 Overflow
IA32_FIXED_CTR0 Overflow
55
35 34 33 32 31
N .. .. 1 0
IA32_PMC(N-1) Overflow
...................... Overflow
IA32_PMC1 Overflow
IA32_PMC0 Overflow
Reserved
Figure 18-10. IA32_PERF_GLOBAL_STATUS MSR and Architectural Perfmon Version 4
Note, a processor’s support for IA32_PERF_GLOBAL_STATUS.TraceToPAPMI[bit 55] is enumerated as a result of
CPUID enumerated capability of Intel Processor Trace and the use of the ToPA buffer scheme. Support of
IA32_PERF_GLOBAL_STATUS.ASCI[bit 60] is enumerated by the CPUID enumeration of Intel SGX.
18.2.4.2
IA32_PERF_GLOBAL_STATUS_RESET and IA32_PERF_GLOBAL_STATUS_SET MSRS
With architectural performance monitoring version 3 and lower, clearing of the set bits in
IA32_PERF_GLOBAL_STATUS MSR by software is done via IA32_PERF_GLOBAL_OVF_CTRL MSR. Starting with
architectural performance monitoring version 4, software can manage the overflow and other indicators in
IA32_PERF_GLOBAL_STATUS using separate interfaces to set or clear individual bits.
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PERFORMANCE MONITORING
The address and the architecturally-defined bits of IA32_PERF_GLOBAL_OVF_CTRL is inherited by
IA32_PERF_GLOBAL_STATUS_RESET (see Figure 18-11). Further, IA32_PERF_GLOBAL_STATUS_RESET provides
additional bit fields to clear the new indicators in IA32_PERF_GLOBAL_STATUS described in Section 18.2.4.1.
63 62 61 60 59 58
55
35 34 33 32 31
Clr CondChgd
Clr OvfDSBuffer
Clr OvfUncore
Clr ASCI
Clr CTR_Frz
Clr LBR_Frz
Clr TraceToPAPMI
Clr IA32_FIXED_CTR2 Ovf
Clr IA32_FIXED_CTR1 Ovf
Clr IA32_FIXED_CTR0 Ovf
N .. .. 1 0
Clr IA32_PMC(N-1) Ovf
Clr ...................... Ovf
Clr IA32_PMC1 Ovf
Clr IA32_PMC0 Ovf
Reserved
Figure 18-11. IA32_PERF_GLOBAL_STATUS_RESET MSR and Architectural Perfmon Version 4
The IA32_PERF_GLOBAL_STATUS_SET MSR is introduced with architectural performance monitoring version 4. It
allows software to set individual bits in IA32_PERF_GLOBAL_STATUS. The IA32_PERF_GLOBAL_STATUS_SET
interface can be used by a VMM to virtualize the state of IA32_PERF_GLOBAL_STATUS across VMs.
63 62 61 60 59 58
55
35 34 33 32 31
Set CondChgd
Set OvfDSBuffer
Set OvfUncore
Set ASCI
Set CTR_Frz
Set LBR_Frz
Set TraceToPAPMI
Set IA32_FIXED_CTR2 Ovf
Set IA32_FIXED_CTR1 Ovf
Set IA32_FIXED_CTR0 Ovf
N .. .. 1 0
Set IA32_PMC(N-1) Ovf
Set ...................... Ovf
Set IA32_PMC1 Ovf
Set IA32_PMC0 Ovf
Reserved
Figure 18-12. IA32_PERF_GLOBAL_STATUS_SET MSR and Architectural Perfmon Version 4
18.2.4.3
IA32_PERF_GLOBAL_INUSE MSR
In a contemporary software environment, multiple privileged service agents may wish to employ the processor’s
performance monitoring facilities. The IA32_MISC_ENABLES.PERFMON_AVAILABLE[bit 7] interface could not
serve the need of multiple agent adequately. A white paper, “Performance Monitoring Unit Sharing Guideline”1,
proposed a cooperative sharing protocol that is voluntary for participating software agents.
Architectural performance monitoring version 4 introduces a new MSR, IA32_PERF_GLOBAL_INUSE, that simplifies
the task of multiple cooperating agents to implement the sharing protocol.
The layout of IA32_PERF_GLOBAL_INUSE is shown in Figure 18-13.
1. Available at http://www.intel.com/sdm
Vol. 3B 18-13
PERFORMANCE MONITORING
63
35 34 33 32 31
PMI InUse
FIXED_CTR2 InUse
FIXED_CTR1 InUse
FIXED_CTR0 InUse
N .. .. 1 0
PERFEVTSEL(N-1) InUse
....................... InUse
PERFEVTSEL1 InUse
PERFEVTSEL0 InUse
N = CPUID.0AH:EAX[15:8]
Reserved
Figure 18-13. IA32_PERF_GLOBAL_INUSE MSR and Architectural Perfmon Version 4
The IA32_PERF_GLOBAL_INUSE MSR provides an “InUse” bit for each programmable performance counter and
fixed counter in the processor. Additionally, it includes an indicator if the PMI mechanism has been configured by a
profiling agent.
•
IA32_PERF_GLOBAL_INUSE.PERFEVTSEL0_InUse[bit 0]: This bit reflects the logical state of
(IA32_PERFEVTSEL0[7:0] != 0).
•
IA32_PERF_GLOBAL_INUSE.PERFEVTSEL1_InUse[bit 1]: This bit reflects the logical state of
(IA32_PERFEVTSEL1[7:0] != 0).
•
IA32_PERF_GLOBAL_INUSE.PERFEVTSEL2_InUse[bit 2]: This bit reflects the logical state of
(IA32_PERFEVTSEL2[7:0] != 0).
•
IA32_PERF_GLOBAL_INUSE.PERFEVTSELn_InUse[bit n]: This bit reflects the logical state of
(IA32_PERFEVTSELn[7:0] != 0), n < CPUID.0AH:EAX[15:8].
•
IA32_PERF_GLOBAL_INUSE.FC0_InUse[bit 32]: This bit reflects the logical state of
(IA32_FIXED_CTR_CTRL[1:0] != 0).
•
IA32_PERF_GLOBAL_INUSE.FC1_InUse[bit 33]: This bit reflects the logical state of
(IA32_FIXED_CTR_CTRL[5:4] != 0).
•
IA32_PERF_GLOBAL_INUSE.FC2_InUse[bit 34]: This bit reflects the logical state of
(IA32_FIXED_CTR_CTRL[9:8] != 0).
•
IA32_PERF_GLOBAL_INUSE.PMI_InUse[bit 32]: This bit is set if any one of the following bit is set:
— IA32_PERFEVTSELn.INT[bit 20], n < CPUID.0AH:EAX[15:8];
— IA32_FIXED_CTR_CTRL.ENi_PMI, i = 0, 1, 2;
— IA32_PEBS_ENABLES.EN_PMCi, i = 0, 1, 2, 3
18.2.5
Full-Width Writes to Performance Counter Registers
The general-purpose performance counter registers IA32_PMCx are writable via WRMSR instruction. However, the
value written into IA32_PMCx by WRMSR is the signed extended 64-bit value of the EAX[31:0] input of WRMSR.
A processor that supports full-width writes to the general-purpose performance counters enumerated by
CPUID.0AH:EAX[15:8] will set IA32_PERF_CAPABILITIES[13] to enumerate its full-width-write capability See
Figure 18-49.
If IA32_PERF_CAPABILITIES.FW_WRITE[bit 13] =1, each IA32_PMCi is accompanied by a corresponding alias
address starting at 4C1H for IA32_A_PMC0.
The bit width of the performance monitoring counters is specified in CPUID.0AH:EAX[23:16].
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PERFORMANCE MONITORING
If IA32_A_PMCi is present, the 64-bit input value (EDX:EAX) of WRMSR to IA32_A_PMCi will cause IA32_PMCi to
be updated by:
COUNTERWIDTH = CPUID.0AH:EAX[23:16] bit width of the performance monitoring counter
IA32_PMCi[COUNTERWIDTH-1:32] ← EDX[COUNTERWIDTH-33:0]);
IA32_PMCi[31:0] ← EAX[31:0];
EDX[63:COUNTERWIDTH] are reserved
18.3
PERFORMANCE MONITORING (INTEL® CORE™ SOLO AND INTEL® CORE™ DUO
PROCESSORS)
In Intel Core Solo and Intel Core Duo processors, non-architectural performance monitoring events are
programmed using the same facilities (see Figure 18-1) used for architectural performance events.
Non-architectural performance events use event select values that are model-specific. Event mask (Umask) values
are also specific to event logic units. Some microarchitectural conditions detectable by a Umask value may have
specificity related to processor topology (see Section 8.6, “Detecting Hardware Multi-Threading Support and
Topology,” in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 3A). As a result, the unit
mask field (for example, IA32_PERFEVTSELx[bits 15:8]) may contain sub-fields that specify topology information
of processor cores.
The sub-field layout within the Umask field may support two-bit encoding that qualifies the relationship between a
microarchitectural condition and the originating core. This data is shown in Table 18-2. The two-bit encoding for
core-specificity is only supported for a subset of Umask values (see Chapter 19, “Performance Monitoring Events”)
and for Intel Core Duo processors. Such events are referred to as core-specific events.
Table 18-2. Core Specificity Encoding within a Non-Architectural Umask
IA32_PERFEVTSELx MSRs
Bit 15:14 Encoding
Description
11B
All cores
10B
Reserved
01B
This core
00B
Reserved
Some microarchitectural conditions allow detection specificity only at the boundary of physical processors. Some
bus events belong to this category, providing specificity between the originating physical processor (a bus agent)
versus other agents on the bus. Sub-field encoding for agent specificity is shown in Table 18-3.
Table 18-3. Agent Specificity Encoding within a Non-Architectural Umask
IA32_PERFEVTSELx MSRs
Bit 13 Encoding
Description
0
This agent
1
Include all agents
Some microarchitectural conditions are detectable only from the originating core. In such cases, unit mask does
not support core-specificity or agent-specificity encodings. These are referred to as core-only conditions.
Some microarchitectural conditions allow detection specificity that includes or excludes the action of hardware
prefetches. A two-bit encoding may be supported to qualify hardware prefetch actions. Typically, this applies only
to some L2 or bus events. The sub-field encoding for hardware prefetch qualification is shown in Table 18-4.
Vol. 3B 18-15
PERFORMANCE MONITORING
Table 18-4. HW Prefetch Qualification Encoding within a Non-Architectural Umask
IA32_PERFEVTSELx MSRs
Bit 13:12 Encoding
Description
11B
All inclusive
10B
Reserved
01B
Hardware prefetch only
00B
Exclude hardware prefetch
Some performance events may (a) support none of the three event-specific qualification encodings (b) may
support core-specificity and agent specificity simultaneously (c) or may support core-specificity and hardware
prefetch qualification simultaneously. Agent-specificity and hardware prefetch qualification are mutually exclusive.
In addition, some L2 events permit qualifications that distinguish cache coherent states. The sub-field definition for
cache coherency state qualification is shown in Table 18-5. If no bits in the MESI qualification sub-field are set for
an event that requires setting MESI qualification bits, the event count will not increment.
Table 18-5. MESI Qualification Definitions within a Non-Architectural Umask
IA32_PERFEVTSELx MSRs
Bit Position 11:8
Description
Bit 11
Counts modified state
Bit 10
Counts exclusive state
Bit 9
Counts shared state
Bit 8
Counts Invalid state
18.4
PERFORMANCE MONITORING (PROCESSORS BASED ON INTEL® CORE™
MICROARCHITECTURE)
In addition to architectural performance monitoring, processors based on the Intel Core microarchitecture support
non-architectural performance monitoring events.
Architectural performance events can be collected using general-purpose performance counters. Non-architectural
performance events can be collected using general-purpose performance counters (coupled with two
IA32_PERFEVTSELx MSRs for detailed event configurations), or fixed-function performance counters (see Section
18.4.1). IA32_PERFEVTSELx MSRs are architectural; their layout is shown in Figure 18-1. Starting with Intel Core
2 processor T 7700, fixed-function performance counters and associated counter control and status MSR becomes
part of architectural performance monitoring version 2 facilities (see also Section 18.2.2).
Non-architectural performance events in processors based on Intel Core microarchitecture use event select values
that are model-specific. Valid event mask (Umask) bits are listed in Chapter 19. The UMASK field may contain subfields identical to those listed in Table 18-2, Table 18-3, Table 18-4, and Table 18-5. One or more of these subfields may apply to specific events on an event-by-event basis. Details are listed in Table 19-23 in Chapter 19,
“Performance-Monitoring Events.”
In addition, the UMASK filed may also contain a sub-field that allows detection specificity related to snoop
responses. Bits of the snoop response qualification sub-field are defined in Table 18-6.
Table 18-6. Bus Snoop Qualification Definitions within a Non-Architectural Umask
IA32_PERFEVTSELx MSRs
Bit Position 11:8
Description
Bit 11
HITM response
Bit 10
Reserved
18-16 Vol. 3B
PERFORMANCE MONITORING
Table 18-6. Bus Snoop Qualification Definitions within a Non-Architectural Umask
IA32_PERFEVTSELx MSRs
Bit Position 11:8
Description
Bit 9
HIT response
Bit 8
CLEAN response
There are also non-architectural events that support qualification of different types of snoop operation. The corresponding bit field for snoop type qualification are listed in Table 18-7.
Table 18-7. Snoop Type Qualification Definitions within a Non-Architectural Umask
IA32_PERFEVTSELx MSRs
Bit Position 9:8
Description
Bit 9
CMP2I snoops
Bit 8
CMP2S snoops
No more than one sub-field of MESI, snoop response, and snoop type qualification sub-fields can be supported in a
performance event.
NOTE
Software must write known values to the performance counters prior to enabling the counters. The
content of general-purpose counters and fixed-function counters are undefined after INIT or
RESET.
18.4.1
Fixed-function Performance Counters
Processors based on Intel Core microarchitecture provide three fixed-function performance counters. Bits beyond
the width of the fixed counter are reserved and must be written as zeros. Model-specific fixed-function performance counters on processors that support Architectural Perfmon version 1 are 40 bits wide.
Each of the fixed-function counter is dedicated to count a pre-defined performance monitoring events. The performance monitoring events associated with fixed-function counters and the addresses of these counters are listed in
Table 18-8.
Table 18-8. Association of Fixed-Function Performance Counters with Architectural Performance Events
Event Name
Fixed-Function PMC
PMC Address
INST_RETIRED.ANY
MSR_PERF_FIXED_CTR0/IA32_FIXED_CTR0
309H
CPU_CLK_UNHALTED.CORE
MSR_PERF_FIXED_CTR1//IA32_FIXED_CTR1
30AH
CPU_CLK_UNHALTED.REF
MSR_PERF_FIXED_CTR2//IA32_FIXED_CTR2
30BH
Programming the fixed-function performance counters does not involve any of the IA32_PERFEVTSELx MSRs, and
does not require specifying any event masks. Instead, the MSR MSR_PERF_FIXED_CTR_CTRL provides multiple
sets of 4-bit fields; each 4-bit field controls the operation of a fixed-function performance counter (PMC). See
Figures 18-14. Two sub-fields are defined for each control. See Figure 18-14; bit fields are:
•
Enable field (low 2 bits in each 4-bit control) — When bit 0 is set, performance counting is enabled in the
corresponding fixed-function performance counter to increment when the target condition associated with the
architecture performance event occurs at ring 0.
When bit 1 is set, performance counting is enabled in the corresponding fixed-function performance counter to
increment when the target condition associated with the architecture performance event occurs at ring greater
than 0.
Vol. 3B 18-17
PERFORMANCE MONITORING
Writing 0 to both bits stops the performance counter. Writing 11B causes the counter to increment irrespective
of privilege levels.
63
12 11
9 8 7
P
M
I
P
M
I
E
N
5 43 2 1 0
E
N
P
M
I
E
N
Cntr2 — Controls for MSR_PERF_FIXED_CTR2
Cntr1 — Controls for MSR_PERF_FIXED_CTR1
PMI — Enable PMI on overflow
Cntr0 — Controls for MSR_PERF_FIXED_CTR0
ENABLE — 0: disable; 1: OS; 2: User; 3: All ring levels
Reserved
Figure 18-14. Layout of MSR_PERF_FIXED_CTR_CTRL MSR
•
PMI field (fourth bit in each 4-bit control) — When set, the logical processor generates an exception
through its local APIC on overflow condition of the respective fixed-function counter.
18.4.2
Global Counter Control Facilities
Processors based on Intel Core microarchitecture provides simplified performance counter control that simplifies
the most frequent operations in programming performance events, i.e. enabling/disabling event counting and
checking the status of counter overflows. This is done by the following three MSRs:
•
MSR_PERF_GLOBAL_CTRL enables/disables event counting for all or any combination of fixed-function PMCs
(MSR_PERF_FIXED_CTRx) or general-purpose PMCs via a single WRMSR.
•
MSR_PERF_GLOBAL_STATUS allows software to query counter overflow conditions on any combination of
fixed-function PMCs (MSR_PERF_FIXED_CTRx) or general-purpose PMCs via a single RDMSR.
•
MSR_PERF_GLOBAL_OVF_CTRL allows software to clear counter overflow conditions on any combination of
fixed-function PMCs (MSR_PERF_FIXED_CTRx) or general-purpose PMCs via a single WRMSR.
MSR_PERF_GLOBAL_CTRL MSR provides single-bit controls to enable counting in each performance counter (see
Figure 18-15). Each enable bit in MSR_PERF_GLOBAL_CTRL is AND’ed with the enable bits for all privilege levels in
the respective IA32_PERFEVTSELx or MSR_PERF_FIXED_CTR_CTRL MSRs to start/stop the counting of respective
counters. Counting is enabled if the AND’ed results is true; counting is disabled when the result is false.
63
35 34 33 32 31
FIXED_CTR2 enable
FIXED_CTR1 enable
FIXED_CTR0 enable
PMC1 enable
PMC0 enable
Reserved
Figure 18-15. Layout of MSR_PERF_GLOBAL_CTRL MSR
18-18 Vol. 3B
2 10
PERFORMANCE MONITORING
MSR_PERF_GLOBAL_STATUS MSR provides single-bit status used by software to query the overflow condition of
each performance counter. MSR_PERF_GLOBAL_STATUS[bit 62] indicates overflow conditions of the DS area data
buffer. MSR_PERF_GLOBAL_STATUS[bit 63] provides a CondChgd bit to indicate changes to the state of performance monitoring hardware (see Figure 18-16). A value of 1 in bits 34:32, 1, 0 indicates an overflow condition has
occurred in the associated counter.
63 62
35 34 33 32 31
2 10
CondChgd
OvfBuffer
FIXED_CTR2 Overflow
FIXED_CTR1 Overflow
FIXED_CTR0 Overflow
PMC1 Overflow
PMC0 Overflow
Reserved
Figure 18-16. Layout of MSR_PERF_GLOBAL_STATUS MSR
When a performance counter is configured for PEBS, an overflow condition in the counter will arm PEBS. On the
subsequent event following overflow, the processor will generate a PEBS event. On a PEBS event, the processor will
perform bounds checks based on the parameters defined in the DS Save Area (see Section 17.4.9). Upon
successful bounds checks, the processor will store the data record in the defined buffer area, clear the counter
overflow status, and reload the counter. If the bounds checks fail, the PEBS will be skipped entirely. In the event
that the PEBS buffer fills up, the processor will set the OvfBuffer bit in MSR_PERF_GLOBAL_STATUS.
MSR_PERF_GLOBAL_OVF_CTL MSR allows software to clear overflow the indicators for general-purpose or fixedfunction counters via a single WRMSR (see Figure 18-17). Clear overflow indications when:
•
•
•
Setting up new values in the event select and/or UMASK field for counting or interrupt-based event sampling.
Reloading counter values to continue collecting next sample.
Disabling event counting or interrupt-based event sampling.
63 62
35 34 33 32 31
2 1 0
ClrCondChgd
ClrOvfBuffer
FIXED_CTR2 ClrOverflow
FIXED_CTR1 ClrOverflow
FIXED_CTR0 ClrOverflow
PMC1 ClrOverflow
PMC0 ClrOverflow
Reserved
Figure 18-17. Layout of MSR_PERF_GLOBAL_OVF_CTRL MSR
Vol. 3B 18-19
PERFORMANCE MONITORING
18.4.3
At-Retirement Events
Many non-architectural performance events are impacted by the speculative nature of out-of-order execution. A
subset of non-architectural performance events on processors based on Intel Core microarchitecture are enhanced
with a tagging mechanism (similar to that found in Intel NetBurst® microarchitecture) that exclude contributions
that arise from speculative execution. The at-retirement events available in processors based on Intel Core microarchitecture does not require special MSR programming control (see Section 18.14.6, “At-Retirement Counting”),
but is limited to IA32_PMC0. See Table 18-9 for a list of events available to processors based on Intel Core microarchitecture.
Table 18-9. At-Retirement Performance Events for Intel Core Microarchitecture
Event Name
UMask
Event Select
ITLB_MISS_RETIRED
00H
C9H
MEM_LOAD_RETIRED.L1D_MISS
01H
CBH
MEM_LOAD_RETIRED.L1D_LINE_MISS
02H
CBH
MEM_LOAD_RETIRED.L2_MISS
04H
CBH
MEM_LOAD_RETIRED.L2_LINE_MISS
08H
CBH
MEM_LOAD_RETIRED.DTLB_MISS
10H
CBH
18.4.4
Processor Event Based Sampling (PEBS)
Processors based on Intel Core microarchitecture also support processor event based sampling (PEBS). This
feature was introduced by processors based on Intel NetBurst microarchitecture.
PEBS uses a debug store mechanism and a performance monitoring interrupt to store a set of architectural state
information for the processor. The information provides architectural state of the instruction executed after the
instruction that caused the event (See Section 18.4.4.2 and Section 17.4.9).
In cases where the same instruction causes BTS and PEBS to be activated, PEBS is processed before BTS are
processed. The PMI request is held until the processor completes processing of PEBS and BTS.
For processors based on Intel Core microarchitecture, precise events that can be used with PEBS are listed in
Table 18-10. The procedure for detecting availability of PEBS is the same as described in Section 18.14.7.1.
Table 18-10. PEBS Performance Events for Intel Core Microarchitecture
Event Name
UMask
Event Select
INSTR_RETIRED.ANY_P
00H
C0H
X87_OPS_RETIRED.ANY
FEH
C1H
BR_INST_RETIRED.MISPRED
00H
C5H
SIMD_INST_RETIRED.ANY
1FH
C7H
MEM_LOAD_RETIRED.L1D_MISS
01H
CBH
MEM_LOAD_RETIRED.L1D_LINE_MISS
02H
CBH
MEM_LOAD_RETIRED.L2_MISS
04H
CBH
MEM_LOAD_RETIRED.L2_LINE_MISS
08H
CBH
MEM_LOAD_RETIRED.DTLB_MISS
10H
CBH
18-20 Vol. 3B
PERFORMANCE MONITORING
18.4.4.1
Setting up the PEBS Buffer
For processors based on Intel Core microarchitecture, PEBS is available using IA32_PMC0 only. Use the following
procedure to set up the processor and IA32_PMC0 counter for PEBS:
1. Set up the precise event buffering facilities. Place values in the precise event buffer base, precise event index,
precise event absolute maximum, precise event interrupt threshold, and precise event counter reset fields of
the DS buffer management area. In processors based on Intel Core microarchitecture, PEBS records consist of
64-bit address entries. See Figure 17-8 to set up the precise event records buffer in memory.
2. Enable PEBS. Set the Enable PEBS on PMC0 flag (bit 0) in IA32_PEBS_ENABLE MSR.
3. Set up the IA32_PMC0 performance counter and IA32_PERFEVTSEL0 for an event listed in Table 18-10.
18.4.4.2
PEBS Record Format
The PEBS record format may be extended across different processor implementations. The
IA32_PERF_CAPABILITES MSR defines a mechanism for software to handle the evolution of PEBS record format in
processors that support architectural performance monitoring with version id equals 2 or higher. The bit fields of
IA32_PERF_CAPABILITES are defined in Table 35-2 of Chapter 35, “Model-Specific Registers (MSRs)”. The relevant
bit fields that governs PEBS are:
•
PEBSTrap [bit 6]: When set, PEBS recording is trap-like. After the PEBS-enabled counter has overflowed, PEBS
record is recorded for the next PEBS-able event at the completion of the sampled instruction causing the PEBS
event. When clear, PEBS recording is fault-like. The PEBS record is recorded before the sampled instruction
causing the PEBS event.
•
PEBSSaveArchRegs [bit 7]: When set, PEBS will save architectural register and state information according to
the encoded value of the PEBSRecordFormat field. When clear, only the return instruction pointer and flags are
recorded. On processors based on Intel Core microarchitecture, this bit is always 1
•
PEBSRecordFormat [bits 11:8]: Valid encodings are:
— 0000B: Only general-purpose registers, instruction pointer and RFLAGS registers are saved in each PEBS
record (seeSection 18.14.7).
— 0001B: PEBS record includes additional information of IA32_PERF_GLOBAL_STATUS and load latency data.
(seeSection 18.8.1.1).
— 0010B: PEBS record includes additional information of IA32_PERF_GLOBAL_STATUS, load latency data,
and TSX tuning information. (seeSection 18.11.2).
— 0011B: PEBS record includes additional information of load latency data, TSX tuning information, TSC data,
and the applicable counter field replaces IA32_PERF_GLOBAL_STATUS at offset 90H. (see Section
18.13.1.1).
18.4.4.3
Writing a PEBS Interrupt Service Routine
The PEBS facilities share the same interrupt vector and interrupt service routine (called the DS ISR) with the Interrupt-based event sampling and BTS facilities. To handle PEBS interrupts, PEBS handler code must be included in
the DS ISR. See Section 17.4.9.1, “64 Bit Format of the DS Save Area,” for guidelines when writing the DS ISR.
The service routine can query MSR_PERF_GLOBAL_STATUS to determine which counter(s) caused of overflow
condition. The service routine should clear overflow indicator by writing to MSR_PERF_GLOBAL_OVF_CTL.
Vol. 3B 18-21
PERFORMANCE MONITORING
A comparison of the sequence of requirements to program PEBS for processors based on Intel Core and Intel
NetBurst microarchitectures is listed in Table 18-11.
Table 18-11. Requirements to Program PEBS
For Processors based on Intel Core
microarchitecture
For Processors based on Intel NetBurst
microarchitecture
Verify PEBS support of
processor/OS
• IA32_MISC_ENABLE.EMON_AVAILABE (bit 7) is set.
• IA32_MISC_ENABLE.PEBS_UNAVAILABE (bit 12) is clear.
Ensure counters are in disabled
On initial set up or changing event
configurations, write
MSR_PERF_GLOBAL_CTRL MSR (38FH) with 0.
Optional
On subsequent entries:
• Clear all counters if “Counter Freeze on PMI“
is not enabled.
• If IA32_DebugCTL.Freeze is enabled,
counters are automatically disabled.
Counters MUST be stopped before writing.1
Disable PEBS.
Clear ENABLE PMC0 bit in IA32_PEBS_ENABLE
MSR (3F1H).
Optional
Check overflow conditions.
Check MSR_PERF_GLOBAL_STATUS MSR
(38EH) handle any overflow conditions.
Check OVF flag of each CCCR for overflow
condition
Clear overflow status.
Clear MSR_PERF_GLOBAL_STATUS MSR
(38EH) using IA32_PERF_GLOBAL_OVF_CTRL
MSR (390H).
Clear OVF flag of each CCCR.
Write “sample-after“ values.
Configure the counter(s) with the sample after value.
Configure specific counter
configuration MSR.
• Set local enable bit 22 - 1.
• Do NOT set local counter PMI/INT bit, bit 20
- 0.
• Event programmed must be PEBS capable.
Allocate buffer for PEBS states.
Allocate a buffer in memory for the precise information.
Program the IA32_DS_AREA MSR.
Program the IA32_DS_AREA MSR.
Configure the PEBS buffer
management records.
Configure the PEBS buffer management records in the DS buffer management area.
Configure/Enable PEBS.
Set Enable PMC0 bit in IA32_PEBS_ENABLE
MSR (3F1H).
Configure MSR_PEBS_ENABLE,
MSR_PEBS_MATRIX_VERT and
MSR_PEBS_MATRIX_HORZ as needed.
Enable counters.
Set Enable bits in MSR_PERF_GLOBAL_CTRL
MSR (38FH).
Set each CCCR enable bit 12 - 1.
• Set appropriate OVF_PMI bits - 1.
• Only CCCR for MSR_IQ_COUNTER4 support
PEBS.
NOTES:
1. Counters read while enabled are not guaranteed to be precise with event counts that occur in timing proximity to the RDMSR.
18.4.4.4
Re-configuring PEBS Facilities
When software needs to reconfigure PEBS facilities, it should allow a quiescent period between stopping the prior
event counting and setting up a new PEBS event. The quiescent period is to allow any latent residual PEBS records
to complete its capture at their previously specified buffer address (provided by IA32_DS_AREA).
18-22 Vol. 3B
PERFORMANCE MONITORING
18.5
PERFORMANCE MONITORING (45 NM AND 32 NM INTEL® ATOM™
PROCESSORS)
45 nm and 32 nm Intel Atom processors report architectural performance monitoring versionID = 3 (supporting
the aggregate capabilities of versionID 1, 2, and 3; see Section 18.2.3) and a host of non-architectural monitoring
capabilities. These 45 nm and 32 nm Intel Atom processors provide two general-purpose performance counters
(IA32_PMC0, IA32_PMC1) and three fixed-function performance counters (IA32_FIXED_CTR0,
IA32_FIXED_CTR1, IA32_FIXED_CTR2).
Non-architectural performance monitoring in Intel Atom processor family uses the IA32_PERFEVTSELx MSR to
configure a set of non-architecture performance monitoring events to be counted by the corresponding generalpurpose performance counter. The list of non-architectural performance monitoring events is listed in Table 19-26.
Architectural and non-architectural performance monitoring events in 45 nm and 32 nm Intel Atom processors
support thread qualification using bit 21 (AnyThread) of IA32_PERFEVTSELx MSR, i.e. if
IA32_PERFEVTSELx.AnyThread =1, event counts include monitored conditions due to either logical processors in
the same processor core.
The bit fields within each IA32_PERFEVTSELx MSR are defined in Figure 18-6 and described in Section 18.2.1.1 and
Section 18.2.3.
Valid event mask (Umask) bits are listed in Chapter 19. The UMASK field may contain sub-fields that provide the
same qualifying actions like those listed in Table 18-2, Table 18-3, Table 18-4, and Table 18-5. One or more of
these sub-fields may apply to specific events on an event-by-event basis. Details are listed in Table 19-26 in
Chapter 19, “Performance-Monitoring Events.” Precise Event Based Monitoring is supported using IA32_PMC0 (see
also Section 17.4.9, “BTS and DS Save Area”).
18.6
PERFORMANCE MONITORING FOR SILVERMONT MICROARCHITECTURE
Intel processors based on the Silvermont microarchitecture report architectural performance monitoring versionID
= 3 (see Section 18.2.3) and a host of non-architectural monitoring capabilities. Intel processors based on the
Silvermont microarchitecture provide two general-purpose performance counters (IA32_PMC0, IA32_PMC1) and
three fixed-function performance counters (IA32_FIXED_CTR0, IA32_FIXED_CTR1, IA32_FIXED_CTR2). Intel
Atom processors based on the Airmont microarchitecture support the same performance monitoring capabilities as
those based on the Silvermont microarchitecture.
Non-architectural performance monitoring in the Silvermont microarchitecture uses the IA32_PERFEVTSELx MSR
to configure a set of non-architecture performance monitoring events to be counted by the corresponding generalpurpose performance counter. The list of non-architectural performance monitoring events is listed in Table 19-25.
The bit fields (except bit 21) within each IA32_PERFEVTSELx MSR are defined in Figure 18-6 and described in
Section 18.2.1.1 and Section 18.2.3. Architectural and non-architectural performance monitoring events in the
Silvermont microarchitecture ignore the AnyThread qualification regardless of its setting in IA32_PERFEVTSELx
MSR.
18.6.1
Enhancements of Performance Monitoring in the Processor Core
The notable enhancements in the monitoring of performance events in the processor core include:
•
•
The width of counter reported by CPUID.0AH:EAX[23:16] is 40 bits.
•
Average request latency measurement. The off-core response counting facility can be combined to use two
performance counters to count the occurrences and weighted cycles of transaction requests.
Off-core response counting facility. This facility in the processor core allows software to count certain
transaction responses between the processor core to sub-systems outside the processor core (uncore).
Counting off-core response requires additional event qualification configuration facility in conjunction with
IA32_PERFEVTSELx. Two off-core response MSRs are provided to use in conjunction with specific event codes
that must be specified with IA32_PERFEVTSELx.
Vol. 3B 18-23
PERFORMANCE MONITORING
18.6.1.1
Processor Event Based Sampling (PEBS)
In the Silvermont microarchitecture, the PEBS facility can be used with precise events. PEBS is supported using
IA32_PMC0 (see also Section 17.4.9).
PEBS uses a debug store mechanism to store a set of architectural state information for the processor. The information provides architectural state of the instruction executed after the instruction that caused the event (See
Section 18.4.4).
The list of precise events supported in the Silvermont microarchitecture is shown in Table 18-12.
Table 18-12. PEBS Performance Events for the Silvermont Microarchitecture
Event Name
Event Select
Sub-event
UMask
BR_INST_RETIRED
C4H
ALL_BRANCHES
00H
JCC
7EH
TAKEN_JCC
FEH
BR_MISP_RETIRED
MEM_UOPS_RETIRED
REHABQ
18-24 Vol. 3B
C5H
04H
03H
CALL
F9H
REL_CALL
FDH
IND_CALL
FBH
NON_RETURN_IND
EBH
FAR_BRANCH
BFH
RETURN
F7H
ALL_BRANCHES
00H
JCC
7EH
TAKEN_JCC
FEH
IND_CALL
FBH
NON_RETURN_IND
EBH
RETURN
F7H
L2_HIT_LOADS
02H
L2_MISS_LOADS
04H
DLTB_MISS_LOADS
08H
HITM
20H
LD_BLOCK_ST_FORWARD
01H
LD_SPLITS
08H
PERFORMANCE MONITORING
PEBS Record Format The PEBS record format supported by processors based on the Intel Silvermont microarchitecture is shown in Table 18-13, and each field in the PEBS record is 64 bits long.
Table 18-13. PEBS Record Format for the Silvermont Microarchitecture
Byte Offset
Field
Byte Offset
Field
00H
R/EFLAGS
60H
R10
08H
R/EIP
68H
R11
10H
R/EAX
70H
R12
18H
R/EBX
78H
R13
20H
R/ECX
80H
R14
28H
R/EDX
88H
R15
30H
R/ESI
90H
IA32_PERF_GLOBAL_STATUS
38H
R/EDI
98H
Reserved
40H
R/EBP
A0H
Reserved
48H
R/ESP
A8H
Reserved
50H
R8
B0H
EventingRIP
58H
R9
B8H
Reserved
18.6.2
Offcore Response Event
Event number 0B7H support offcore response monitoring using an associated configuration MSR,
MSR_OFFCORE_RSP0 (address 1A6H) in conjunction with umask value 01H or MSR_OFFCORE_RSP1 (address
1A7H) in conjunction with umask value 02H. Table 18-14 lists the event code, mask value and additional off-core
configuration MSR that must be programmed to count off-core response events using IA32_PMCx.
In the Silvermont microarchitecture, each MSR_OFFCORE_RSPx is shared by two processor cores.
Table 18-14. OffCore Response Event Encoding
Counter
Event code
UMask
Required Off-core Response MSR
PMC0-1
B7H
01H
MSR_OFFCORE_RSP0 (address 1A6H)
PMC0-1
B7H
02H
MSR_OFFCORE_RSP1 (address 1A7H)
The layout of MSR_OFFCORE_RSP0 and MSR_OFFCORE_RSP1 are shown in Figure 18-18 and Figure 18-19. Bits
15:0 specifies the request type of a transaction request to the uncore. Bits 30:16 specifies supplier information,
bits 37:31 specifies snoop response information.
Additionally, MSR_OFFCORE_RSP0 provides bit 38 to enable measurement of average latency of specific type of
offcore transaction requests using two programmable counter simultaneously, see Section 18.6.3 for details.
Vol. 3B 18-25
PERFORMANCE MONITORING
63
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
37
See Figure 18-30
RESPONSE TYPE — Other (R/W)
REQUEST TYPE — PARTIAL_STRM_ST (R/W)
REQUEST TYPE — PF_DATA_RD (R/W)
REQUEST TYPE — SW_PREFETCH (R/W)
REQUEST TYPE — STRM_ST (R/W)
REQUEST TYPE — BUS_LOCKS (R/W)
REQUEST TYPE — UC_IFETCH (R/W)
REQUEST TYPE — PARTIAL_WRITE (R/W)
REQUEST TYPE — PARTIAL_READ (R/W)
REQUEST TYPE — PF_IFETCH (R/W)
REQUEST TYPE — PF_RFO (R/W)
REQUEST TYPE — PF_DATA_RD (R/W)
REQUEST TYPE — WB (R/W)
REQUEST TYPE — DMND_IFETCH (R/W)
REQUEST TYPE — DMND_RFO (R/W)
REQUEST TYPE — DMND_DATA_RD (R/W)
Reserved
RESET Value — 00000000_00000000H
Figure 18-18. Request_Type Fields for MSR_OFFCORE_RSPx
Table 18-15. MSR_OFFCORE_RSPx Request_Type Field Definition
Bit Name
Offset
Description
DMND_DATA_RD
0
(R/W). Counts the number of demand and DCU prefetch data reads of full and partial cachelines as
well as demand data page table entry cacheline reads. Does not count L2 data read prefetches or
instruction fetches.
DMND_RFO
1
(R/W). Counts the number of demand and DCU prefetch reads for ownership (RFO) requests
generated by a write to data cacheline. Does not count L2 RFO prefetches.
DMND_IFETCH
2
(R/W). Counts the number of demand and DCU prefetch instruction cacheline reads. Does not count
L2 code read prefetches.
WB
3
(R/W). Counts the number of writeback (modified to exclusive) transactions.
PF_DATA_RD
4
(R/W). Counts the number of data cacheline reads generated by L2 prefetchers.
PF_RFO
5
(R/W). Counts the number of RFO requests generated by L2 prefetchers.
PF_IFETCH
6
(R/W). Counts the number of code reads generated by L2 prefetchers.
PARTIAL_READ
7
(R/W). Counts the number of demand reads of partial cache lines (including UC and WC).
PARTIAL_WRITE
8
(R/W). Counts the number of demand RFO requests to write to partial cache lines (includes UC, WT
and WP)
UC_IFETCH
9
(R/W). Counts the number of UC instruction fetches.
BUS_LOCKS
10
(R/W). Bus lock and split lock requests
STRM_ST
11
(R/W). Streaming store requests
SW_PREFETCH
12
(R/W). Counts software prefetch requests
PF_DATA_RD
13
(R/W). Counts DCU hardware prefetcher data read requests
PARTIAL_STRM_ST
14
(R/W). Streaming store requests
ANY
15
(R/W). Any request that crosses IDI, including I/O.
18-26 Vol. 3B
PERFORMANCE MONITORING
63
38 37 36 35 34 33 32 31
22 21 20 19 18 17 16
AVG LATENCY — ENABLE AVG LATENCY(R/W)
RESPONSE TYPE — NON_DRAM (R/W)
RSPNS_SNOOP — HITM (R/W)
RESERVED
RSPNS_SNOOP — SNOOP_HIT (R/W)
RSPNS_SNOOP — SNOOP_MISS (R/W)
RESERVED
RSPNS_SNOOP — SNOOP_NONE (R/W)
RESERVED
RSPNS_SUPPLIER — L2_HIT (R/W)
RESERVED
RSPNS_SUPPLIER — ANY (R/W)
Reserved
RESET Value — 00000000_00000000H
Figure 18-19. Response_Supplier and Snoop Info Fields for MSR_OFFCORE_RSPx
To properly program this extra register, software must set at least one request type bit (Table 18-15) and a valid
response type pattern (Table 18-16, Table 18-17). Otherwise, the event count reported will be zero. It is permissible and useful to set multiple request and response type bits in order to obtain various classes of off-core
response events. Although MSR_OFFCORE_RSPx allow an agent software to program numerous combinations that
meet the above guideline, not all combinations produce meaningful data.
Table 18-16. MSR_OFFCORE_RSP_x Response Supplier Info Field Definition
Subtype
Bit Name
Offset
Description
Common
ANY_RESPONSE
16
(R/W). Catch all value for any response types.
Supplier Info
Reserved
17
Reserved
L2_HIT
18
(R/W). Cache reference hit L2 in either M/E/S states.
Reserved
30:19
Reserved
To specify a complete offcore response filter, software must properly program bits in the request and response type
fields. A valid request type must have at least one bit set in the non-reserved bits of 15:0. A valid response type
must be a non-zero value of the following expression:
ANY | [(‘OR’ of Supplier Info Bits) & (‘OR’ of Snoop Info Bits)]
If “ANY” bit is set, the supplier and snoop info bits are ignored.
Vol. 3B 18-27
PERFORMANCE MONITORING
Table 18-17. MSR_OFFCORE_RSPx Snoop Info Field Definition
Subtype
Bit Name
Offset
Description
Snoop
Info
SNP_NONE
31
(R/W). No details on snoop-related information
Reserved
32
Reserved
SNOOP_MISS
33
(R/W). Counts the number of snoop misses when L2 misses
SNOOP_HIT
34
(R/W). Counts the number of snoops hit in the other module where no modified copies
were found
Reserved
35
Reserved
HITM
36
(R/W). Counts the number of snoops hit in the other module where modified copies
were found in other core's L1 cache.
NON_DRAM
37
(R/W). Target was non-DRAM system address. This includes MMIO transactions.
AVG_LATENCY
38
(R/W). Enable average latency measurement by counting weighted cycles of
outstanding offcore requests of the request type specified in bits 15:0 and any
response (bits 37:16 cleared to 0).
This bit is available in MSR_OFFCORE_RESP0. The weighted cycles is accumulated in the
specified programmable counter IA32_PMCx and the occurrence of specified requests
are counted in the other programmable counter.
18.6.3
Average Offcore Request Latency Measurement
Average latency for offcore transactions can be determined by using both MSR_OFFCORE_RSP registers. Using two
performance monitoring counters, program the two OFFCORE_RESPONSE event encodings into the corresponding
IA32_PERFEVTSELx MSRs. Count the weighted cycles via MSR_OFFCORE_RSP0 by programming a request type in
MSR_OFFCORE_RSP0.[15:0] and setting MSR_OFFCORE_RSP0.OUTSTANDING[38] to 1, white setting the
remaining bits to 0. Count the number of requests via MSR_OFFCORE_RSP1 by programming the same request
type from MSR_OFFCORE_RSP0 into MSR_OFFCORE_RSP1[bit 15:0], and setting
MSR_OFFCORE_RSP1.ANY_RESPONSE[16] = 1, while setting the remaining bits to 0. The average latency can be
obtained by dividing the value of the IA32_PMCx register that counted weight cycles by the register that counted
requests.
18.7
PERFORMANCE MONITORING FOR GOLDMONT MICROARCHITECTURE
Next generation Intel Atom processors are based on the Goldmont microarchitecture. They report architectural
performance monitoring versionID = 4 (see Section 18.2.4) and support non-architectural monitoring capabilities
described in this section.
Architectural performance monitoring version 4 capabilities are described in Section 18.2.4.
The bit fields (except bit 21) within each IA32_PERFEVTSELx MSR are defined in Figure 18-6 and described in
Section 18.2.1.1 and Section 18.2.3. Architectural and non-architectural performance monitoring events in the
Goldmont microarchitecture ignore the AnyThread qualification regardless of its setting in the IA32_PERFEVTSELx
MSR.
The core PMU’s capability is similar to that of the Silvermont microarchitecture described in Section 18.6 , with
some differences and enhancements summarized in Table 18-18.
18-28 Vol. 3B
PERFORMANCE MONITORING
Table 18-18. Core PMU Comparison Between the Goldmont and Silvermont Microarchitectures
Box
The Goldmont microarchitecture
The Silvermont microarchitecture
Comment
# of Fixed counters per core
3
3
Use CPUID to enumerate
# of counters.
# of general-purpose
counters per core
4
2
Counter width (R,W)
R:48, W: 32/48
R:40, W:32
See Section 18.2.2.
Architectural Performance
Monitoring version ID
4
3
Use CPUID to enumerate
# of counters.
PMI Overhead Mitigation
• Freeze_Perfmon_on_PMI with
streamlined semantics.
• Freeze_on_LBR with legacy
semantics for branch profiling.
• Freeze_while_SMM.
• Freeze_Perfmon_on_PMI with
legacy semantics.
• Freeze_on_LBR with legacy
semantics for branch profiling.
• Freeze_while_SMM.
See Section 17.4.7.
Counter and Buffer
Overflow Status
Management
• Query via
IA32_PERF_GLOBAL_STATUS
• Reset via
IA32_PERF_GLOBAL_STATUS_R
ESET
• Set via
IA32_PERF_GLOBAL_STATUS_S
ET
• Query via
IA32_PERF_GLOBAL_STATUS
• Reset via
IA32_PERF_GLOBAL_OVF_CTRL
See Section 18.2.4.
IA32_PERF_GLOBAL_STATU
S Indicators of
Overflow/Overhead/Interfer
ence
•
•
•
•
• Individual counter overflow
• PEBS buffer overflow
See Section 18.2.4.
Enable control in
IA32_PERF_GLOBAL_STATU
S
• CTR_Frz,
• LBR_Frz
No
See Section 18.2.4.1.
Perfmon Counter In-Use
Indicator
Query IA32_PERF_GLOBAL_INUSE
No
See Section 18.2.4.3.
Processor Event Based
Sampling (PEBS) Events
General-Purpose Counter 0 only.
Supports all events (precise and
non-precise). Precise events are
listed in Table 18-19.
See Section 18.6.1.1. GeneralPurpose Counter 0 only. Only
supports precise events (see
Table 18-12).
IA32_PMC0 only.
PEBS record format
encoding
0011b
0010b
Reduce skid PEBS
IA32_PMC0 only
No
Data Address Profiling
Yes
No
PEBS record layout
Table 18-20; enhanced fields at
offsets 90H- 98H; and TSC record
field at C0H.
Table 18-13.
PEBS EventingIP
Yes
Yes
Off-core Response Event
MSR 1A6H and 1A7H, each core
has its own register.
MSR 1A6H and 1A7H, shared by a
pair of cores.
Individual counter overflow
PEBS buffer overflow
ToPA buffer overflow
CTR_Frz, LBR_Frz
Legacy semantics not
supported with version 4
or higher.
Nehalem supports 1A6H
only.
Vol. 3B 18-29
PERFORMANCE MONITORING
18.7.1
Processor Event Based Sampling (PEBS)
Processor event based sampling (PEBS) on the Goldmont microarchitecture is enhanced over prior generations
with respect to sampling support of precise events and non-precise events. In the Goldmont microarchitecture,
PEBS is supported using IA32_PMC0 for all events (see Section 17.4.9).
PEBS uses a debug store mechanism to store a set of architectural state information for the processor at the time
the sample was generated.
Precise events work the same way as on the Silvermont microarchitecture. They can capture precise eventingIP associated with a retired instruction that caused the event. The PEBS record provides architectural state of the instruc-
tion executed after the instruction that caused the event (See Section 18.4.4 and Section 17.4.9). The PEBS record
also provides architectural state of the processor after the instruction that caused the event completes. The list of
precise events supported in the Goldmont microarchitecture is shown in Table 18-19.
In the Goldmont microarchitecture, the PEBS facility also supports the use of non-precise events to record
processor state information into PEBS records with the same format as with precise events.
However, a non-precise event may not be attributable to a particular retired instruction or the time of instruction
execution. When the counter overflows, a PEBS record will be generated at the next opportunity. Consider the
event ICACHE.HIT. When the counter overflows, the processor is fetching future instructions. The PEBS record will
be generated at the next opportunity and capture the state at the processor's current retirement point. Other
examples of a non-precise events are CPU_CLK_UNHALTED.CORE_P and HARDWARE_INTERRUPTS.RECEIVED.
There may be many instructions in various stages of execution, multiple or zero instructions being retired each
cycle as CPU_CLK_UNHALTED.CORE_P increments. HARDWARE_INTERRUPTS.RECEIVED increments independent
of any instructions being executed. The PEBS record will be generated at the next opportunity, capturing the
processor state when the machine received the interrupt, even if interrupts are masked. The PEBS facility thus
allows for identification of the instructions which were executing when the event overflowed.
After generating a record, the PEBS facility reloads the counter and resumes execution, just as is done for precise
events. Unlike interrupt-based sampling, which requires an interrupt service routine to collect the sample and
reload the counter, the PEBS facility can collect samples even when interrupts are masked and without using NMI.
Since a PEBS record is generated immediately when a counter for a non-precise event is enabled, it may also be
generated after an overflow is set by an MSR write to IA32_PERF_GLOBAL_STATUS_SET.
Table 18-19. Precise Events Supported by the Goldmont Microarchitecture
Event Name
Event Select
Sub-event
UMask
LD_BLOCKS
03H
DATA_UNKNOWN
01H
STORE_FORWARD
02H
4K_ALIAS
04H
UTLB_MISS
08H
ALL_BLOCK
10H
02H
MISALIGN_MEM_REF
13H
LOAD_PAGE_SPLIT
STORE_PAGE_SPLIT
04H
INST_RETIRED
C0H
ANY
00H
UOPS_RETITRED
C2H
ANY
00H
LD_SPLITSMS
01H
BR_INST_RETIRED
18-30 Vol. 3B
C4H
ALL_BRANCHES
00H
JCC
7EH
TAKEN_JCC
FEH
CALL
F9H
REL_CALL
FDH
IND_CALL
FBH
NON_RETURN_IND
EBH
FAR_BRANCH
BFH
PERFORMANCE MONITORING
Table 18-19. Precise Events Supported by the Goldmont Microarchitecture (Contd.)
Event Name
Event Select
BR_MISP_RETIRED
C5H
MEM_UOPS_RETIRED
D0H
MEM_LOAD_UOPS_RETIRED
D1H
Sub-event
UMask
RETURN
F7H
ALL_BRANCHES
00H
JCC
7EH
TAKEN_JCC
FEH
IND_CALL
FBH
NON_RETURN_IND
EBH
RETURN
F7H
ALL_LOADS
81H
ALL_STORES
82H
ALL
83H
DLTB_MISS_LOADS
11H
DLTB_MISS_STORES
12H
DLTB_MISS
13H
L1_HIT
01H
L2_HIT
02H
L1_MISS
08H
L2_MISS
10H
HITM
20H
WCB_HIT
40H
DRAM_HIT
80H
The PEBS record format supported by processors based on the Intel Silvermont microarchitecture is shown in
Table 18-13, and each field in the PEBS record is 64 bits long.
Table 18-20. PEBS Record Format for the Goldmont Microarchitecture
Byte Offset
Field
Byte Offset
Field
00H
R/EFLAGS
68H
R11
08H
R/EIP
70H
R12
10H
R/EAX
78H
R13
18H
R/EBX
80H
R14
20H
R/ECX
88H
R15
28H
R/EDX
90H
Applicable Counters
30H
R/ESI
98H
Data Linear Address
38H
R/EDI
A0H
Reserved
40H
R/EBP
A8H
Reserved
48H
R/ESP
B0H
EventingRIP
50H
R8
B8H
Reserved
58H
R9
C0H
TSC
60H
R10
On Goldmont microarchitecture, all 64 bits of architectural registers are written into the PEBS record regardless of
processor mode.
Vol. 3B 18-31
PERFORMANCE MONITORING
With PEBS record format encoding 0011b, offset 90H reports the “applicable counter” field, which is a multicounter PEBS resolution index allowing software to correlate the PEBS record entry with the eventing PEBS overflow when multiple counters are configured to record PEBS records. Additionally, offset C0H captures a snapshot of
the TSC that provides a time line annotation for each PEBS record entry.
18.7.1.1
PEBS Data Linear Address Profiling
Goldmont supports the Data Linear Address field introduced in Haswell. It does not support the Data Source
Encoding or Latency Value fields that are also part of Data Address Profiling. The fields are present in the record but
are reserved.
For Goldmont, the Data Linear Address field will record the linear address of memory accesses in the previous
instruction (e.g. the one that triggered a precise event that caused the PEBS record to be generated).
18.7.1.2
Reduced Skid PEBS
For precise events, upon triggering a PEBS assist, there will be a finite delay between the time the counter overflows and when the microcode starts to carry out its data collection obligations. The Reduced Skid mechanism mitigates the “skid” problem by providing an early indication of when the counter is about to overflow, allowing the
machine to more precisely trap on the instruction that actually caused the counter overflow thus greatly reducing
skid.
This mechanism is a superset of the PDIR mechanism available in the Sandy Bridge microarchitecture. See Section
18.9.4.4
In the Goldmont microarchitecture, the mechanism applies to all precise events including INST_RETIRED.
However, the Reduced Skid mechanism is disabled for any counter when the INV, ANY, E, or CMASK fields are set.
To ensure the Reduced Skid mechanism operates correctly, disable PEBS via the IA32_PEBS_ENABLE or
IA32_PERF_GLOBAL_CTRL MSRs before writing to the configuration registers (IA32_PERFEVTSELx) or to the counters (IA32_PMCx and IA32_A_PMCx).
18.7.1.3
Enhancements to IA32_PERF_GLOBAL_STATUS.OvfDSBuffer[62]
In addition to IA32_PERF_GLOBAL_STATUS.OvfDSBuffer[62] being set when PEBS_Index reaches the
PEBS_Interrupt_Theshold, the bit is also set when PEBS_Index is out of bounds. That is, the bit will be set when
PEBS_Index < PEBS_Buffer_Base or PEBS_Index > PEBS_Absolute_Maximum. Note that when an out of bound
condition is encountered, the overflow bits in IA32_PERF_GLOBAL_STATUS will be cleared according to Applicable
Counters, however the IA32_PMCx values will not be reloaded with the Reset values stored in the DS_AREA.
18.7.2
Offcore Response Event
Event number 0B7H support offcore response monitoring using an associated configuration MSR,
MSR_OFFCORE_RSP0 (address 1A6H) in conjunction with umask value 01H or MSR_OFFCORE_RSP1 (address
1A7H) in conjunction with umask value 02H. Table 18-14 lists the event code, mask value and additional off-core
configuration MSR that must be programmed to count off-core response events using IA32_PMCx.
The Goldmont microarchitecture provides unique pairs of MSR_OFFCORE_RSPx registers per core.
The layout of MSR_OFFCORE_RSP0 and MSR_OFFCORE_RSP1 are organized as follows:
•
•
•
Bits 15:0 specifies the request type of a transaction request to the uncore. This is described in Table 18-21.
•
For outstanding requests, bit 38 can enable measurement of average latency of specific type of offcore
transaction requests using two programmable counter simultaneously; see Section 18.6.3 for details.
Bits 30:16 specifies common supplier information or an L2 Hit, and is described in Table 18-16.
If L2 misses, then Bits 37:31 can be used to specify snoop response information and is described in
Table 18-22.
18-32 Vol. 3B
PERFORMANCE MONITORING
Table 18-21. MSR_OFFCORE_RSPx Request_Type Field Definition
Bit Name
Offset
Description
DEMAND_DATA_RD
0
(R/W) Counts cacheline read requests due to demand reads (excludes prefetches).
DEMAND_RFO
1
(R/W) Counts cacheline read for ownership (RFO) requests due to demand writes
(excludes prefetches).
DEMAND_CODE_RD
2
(R/W) Counts demand instruction cacheline and I-side prefetch requests that miss the
instruction cache.
COREWB
3
(R/W) Counts writeback transactions caused by L1 or L2 cache evictions.
PF_L2_DATA_RD
4
(R/W) Counts data cacheline reads generated by hardware L2 cache prefetcher.
PF_L2_RFO
5
(R/W) Counts reads for ownership (RFO) requests generated by L2 prefetcher.
Reserved
6
Reserved.
PARTIAL_READS
7
(R/W) Counts demand data partial reads, including data in uncacheable (UC) or
uncacheable (WC) write combining memory types.
PARTIAL_WRITES
8
(R/W) Counts partial writes, including uncacheable (UC), write through (WT) and write
protected (WP) memory type writes.
UC_CODE_READS
9
(R/W) Counts code reads in uncacheable (UC) memory region.
BUS_LOCKS
10
(R/W) Counts bus lock and split lock requests.
FULL_STREAMING_STORES
11
(R/W) Counts full cacheline writes due to streaming stores.
SW_PREFETCH
12
(R/W) Counts cacheline requests due to software prefetch instructions.
PF_L1_DATA_RD
13
(R/W) Counts data cacheline reads generated by hardware L1 data cache prefetcher.
PARTIAL_STREAMING_STORES
14
(R/W) Counts partial cacheline writes due to streaming stores.
ANY_REQUEST
15
(R/W) Counts requests to the uncore subsystem.
To properly program this extra register, software must set at least one request type bit (Table 18-15) and a valid
response type pattern (either Table 18-16 or Table 18-22). Otherwise, the event count reported will be zero. It is
permissible and useful to set multiple request and response type bits in order to obtain various classes of off-core
response events. Although MSR_OFFCORE_RSPx allow an agent software to program numerous combinations that
meet the above guideline, not all combinations produce meaningful data.
Table 18-22. MSR_OFFCORE_RSPx For L2 Miss and Outstanding Requests
Subtype
Bit Name
Offset
Description
L2_MISS
(Snoop Info)
Reserved
32:31
Reserved
L2_MISS.SNOOP_MISS_O 33
R_NO_SNOOP_NEEDED
(R/W). A true miss to this module, for which a snoop request missed the other
module or no snoop was performed/needed.
L2_MISS.HIT_OTHER_CO
RE_NO_FWD
34
(R/W) A snoop hit in the other processor module, but no data forwarding is
required.
Reserved
35
Reserved
L2_MISS.HITM_OTHER_C 36
ORE
(R/W) Counts the number of snoops hit in the other module or other core's L1
where modified copies were found.
L2_MISS.NON_DRAM
37
(R/W) Target was a non-DRAM system address. This includes MMIO transactions.
38
(R/W) Counts weighted cycles of outstanding offcore requests of the request type
specified in bits 15:0, from the time the XQ receives the request and any
response is received. Bits 37:16 must be set to 0. This bit is only available in
MSR_OFFCORE_RESP0.
Outstanding OUTSTANDING
requests1
Vol. 3B 18-33
PERFORMANCE MONITORING
NOTES:
1. See Section 18.6.3, “Average Offcore Request Latency Measurement” for details on how to use this bit to extract average latency.
To specify a complete offcore response filter, software must properly program bits in the request and response type
fields. A valid request type must have at least one bit set in the non-reserved bits of 15:0. A valid response type
must be a non-zero value of the following expression:
[ANY ‘OR’ (L2 Hit) ] ‘XOR’ ( Snoop Info Bits) ‘XOR’ (Avg Latency)
18.7.3
Average Offcore Request Latency Measurement
In Goldmont microarachitecture, measurement of average latency of offcore transaction requests is the same as
described in Section 18.6.3.
18.8
PERFORMANCE MONITORING FOR PROCESSORS BASED ON INTEL®
MICROARCHITECTURE CODE NAME NEHALEM
Intel Core i7 processor family2 supports architectural performance monitoring capability with version ID 3 (see
Section 18.2.3) and a host of non-architectural monitoring capabilities. The Intel Core i7 processor family is based
on Intel® microarchitecture code name Nehalem, and provides four general-purpose performance counters
(IA32_PMC0, IA32_PMC1, IA32_PMC2, IA32_PMC3) and three fixed-function performance counters
(IA32_FIXED_CTR0, IA32_FIXED_CTR1, IA32_FIXED_CTR2) in the processor core.
Non-architectural performance monitoring in Intel Core i7 processor family uses the IA32_PERFEVTSELx MSR to
configure a set of non-architecture performance monitoring events to be counted by the corresponding generalpurpose performance counter. The list of non-architectural performance monitoring events is listed in Table 19-26.
Non-architectural performance monitoring events fall into two broad categories:
•
Performance monitoring events in the processor core: These include many events that are similar to
performance monitoring events available to processor based on Intel Core microarchitecture. Additionally,
there are several enhancements in the performance monitoring capability for detecting microarchitectural
conditions in the processor core or in the interaction of the processor core to the off-core sub-systems in the
physical processor package. The off-core sub-systems in the physical processor package is loosely referred to
as “uncore“.
•
Performance monitoring events in the uncore: The uncore sub-system is shared by more than one processor
cores in the physical processor package. It provides additional performance monitoring facility outside of
IA32_PMCx and performance monitoring events that are specific to the uncore sub-system.
Architectural and non-architectural performance monitoring events in Intel Core i7 processor family support thread
qualification using bit 21 of IA32_PERFEVTSELx MSR.
The bit fields within each IA32_PERFEVTSELx MSR are defined in Figure 18-6 and described in Section 18.2.1.1 and
Section 18.2.3.
2. Intel Xeon processor 5500 series and 3400 series are also based on Intel microarchitecture code name Nehalem, so the performance monitoring facilities described in this section generally also apply.
18-34 Vol. 3B
PERFORMANCE MONITORING
63 62 61 60
353433 3231
8 7 6 5 43 2 1 0
CHG (R/W)
OVF_PMI (R/W)
OVF_FC2 (R/O)
OVF_FC1 (R/O)
OVF_FC0 (R/O)
OVF_PC7 (R/O), if CCNT>7
OVF_PC6 (R/O), if CCNT>6
OVF_PC5 (R/O), if CCNT>5
OVF_PC4 (R/O), if CCNT>4
OVF_PC3 (R/O)
OVF_PC2 (R/O)
OVF_PC1 (R/O)
OVF_PC0 (R/O)
Reserved
RESET Value — 00000000_00000000H
CCNT: CPUID.AH:EAX[15:8]
Figure 18-20. IA32_PERF_GLOBAL_STATUS MSR
18.8.1
Enhancements of Performance Monitoring in the Processor Core
The notable enhancements in the monitoring of performance events in the processor core include:
•
Four general purpose performance counters, IA32_PMCx, associated counter configuration MSRs,
IA32_PERFEVTSELx, and global counter control MSR supporting simplified control of four counters. Each of the
four performance counter can support processor event based sampling (PEBS) and thread-qualification of
architectural and non-architectural performance events. Width of IA32_PMCx supported by hardware has been
increased. The width of counter reported by CPUID.0AH:EAX[23:16] is 48 bits. The PEBS facility in Intel microarchitecture code name Nehalem has been enhanced to include new data format to capture additional information, such as load latency.
•
Load latency sampling facility. Average latency of memory load operation can be sampled using load-latency
facility in processors based on Intel microarchitecture code name Nehalem. This field measures the load
latency from load's first dispatch of till final data writeback from the memory subsystem. The latency is
reported for retired demand load operations and in core cycles (it accounts for re-dispatches). This facility is
used in conjunction with the PEBS facility.
•
Off-core response counting facility. This facility in the processor core allows software to count certain
transaction responses between the processor core to sub-systems outside the processor core (uncore).
Counting off-core response requires additional event qualification configuration facility in conjunction with
IA32_PERFEVTSELx. Two off-core response MSRs are provided to use in conjunction with specific event codes
that must be specified with IA32_PERFEVTSELx.
18.8.1.1
Processor Event Based Sampling (PEBS)
All four general-purpose performance counters, IA32_PMCx, can be used for PEBS if the performance event
supports PEBS. Software uses IA32_MISC_ENABLE[7] and IA32_MISC_ENABLE[12] to detect whether the performance monitoring facility and PEBS functionality are supported in the processor. The MSR IA32_PEBS_ENABLE
provides 4 bits that software must use to enable which IA32_PMCx overflow condition will cause the PEBS record
to be captured.
Additionally, the PEBS record is expanded to allow latency information to be captured. The MSR
IA32_PEBS_ENABLE provides 4 additional bits that software must use to enable latency data recording in the PEBS
record upon the respective IA32_PMCx overflow condition. The layout of IA32_PEBS_ENABLE for processors based
on Intel microarchitecture code name Nehalem is shown in Figure 18-21.
Vol. 3B 18-35
PERFORMANCE MONITORING
When a counter is enabled to capture machine state (PEBS_EN_PMCx = 1), the processor will write machine state
information to a memory buffer specified by software as detailed below. When the counter IA32_PMCx overflows
from maximum count to zero, the PEBS hardware is armed.
36 3534 33 32 31
63
8 7 6 5 43 2 1 0
LL_EN_PMC3 (R/W)
LL_EN_PMC2 (R/W)
LL_EN_PMC1 (R/W)
LL_EN_PMC0 (R/W)
PEBS_EN_PMC3 (R/W)
PEBS_EN_PMC2 (R/W)
PEBS_EN_PMC1 (R/W)
PEBS_EN_PMC0 (R/W)
Reserved
RESET Value — 00000000_00000000H
Figure 18-21. Layout of IA32_PEBS_ENABLE MSR
Upon occurrence of the next PEBS event, the PEBS hardware triggers an assist and causes a PEBS record to be
written. The format of the PEBS record is indicated by the bit field IA32_PERF_CAPABILITIES[11:8] (see
Figure 18-49).
The behavior of PEBS assists is reported by IA32_PERF_CAPABILITIES[6] (see Figure 18-49). The return instruction pointer (RIP) reported in the PEBS record will point to the instruction after (+1) the instruction that causes the
PEBS assist. The machine state reported in the PEBS record is the machine state after the instruction that causes
the PEBS assist is retired. For instance, if the instructions:
mov eax, [eax] ; causes PEBS assist
nop
are executed, the PEBS record will report the address of the nop, and the value of EAX in the PEBS record will show
the value read from memory, not the target address of the read operation.
The PEBS record format is shown in Table 18-23, and each field in the PEBS record is 64 bits long. The PEBS record
format, along with debug/store area storage format, does not change regardless of IA-32e mode is active or not.
CPUID.01H:ECX.DTES64[bit 2] reports whether the processor's DS storage format support is mode-independent.
When set, it uses 64-bit DS storage format.
18-36 Vol. 3B
PERFORMANCE MONITORING
Table 18-23. PEBS Record Format for Intel Core i7 Processor Family
Byte Offset
Field
Byte Offset
Field
00H
R/EFLAGS
58H
R9
08H
R/EIP
60H
R10
10H
R/EAX
68H
R11
18H
R/EBX
70H
R12
20H
R/ECX
78H
R13
28H
R/EDX
80H
R14
30H
R/ESI
88H
R15
38H
R/EDI
90H
IA32_PERF_GLOBAL_STATUS
40H
R/EBP
98H
Data Linear Address
48H
R/ESP
A0H
Data Source Encoding
50H
R8
A8H
Latency value (core cycles)
In IA-32e mode, the full 64-bit value is written to the register. If the processor is not operating in IA-32e mode, 32bit value is written to registers with bits 63:32 zeroed. Registers not defined when the processor is not in IA-32e
mode are written to zero.
Bytes AFH:90H are enhancement to the PEBS record format. Support for this enhanced PEBS record format is indicated by IA32_PERF_CAPABILITIES[11:8] encoding of 0001B.
The value written to bytes 97H:90H is the state of the IA32_PERF_GLOBAL_STATUS register before the PEBS assist
occurred. This value is written so software can determine which counters overflowed when this PEBS record was
written. Note that this field indicates the overflow status for all counters, regardless of whether they were
programmed for PEBS or not.
Programming PEBS Facility
Only a subset of non-architectural performance events in the processor support PEBS. The subset of precise events
are listed in Table 18-10. In addition to using IA32_PERFEVTSELx to specify event unit/mask settings and setting
the EN_PMCx bit in the IA32_PEBS_ENABLE register for the respective counter, the software must also initialize the
DS_BUFFER_MANAGEMENT_AREA data structure in memory to support capturing PEBS records for precise events.
NOTE
PEBS events are only valid when the following fields of IA32_PERFEVTSELx are all zero: AnyThread,
Edge, Invert, CMask.
The beginning linear address of the DS_BUFFER_MANAGEMENT_AREA data structure must be programmed into
the IA32_DS_AREA register. The layout of the DS_BUFFER_MANAGEMENT_AREA is shown in Figure 18-22.
•
PEBS Buffer Base: This field is programmed with the linear address of the first byte of the PEBS buffer
allocated by software. The processor reads this field to determine the base address of the PEBS buffer.
Software should allocate this memory from the non-paged pool.
•
PEBS Index: This field is initially programmed with the same value as the PEBS Buffer Base field, or the
beginning linear address of the PEBS buffer. The processor reads this field to determine the location of the next
PEBS record to write to. After a PEBS record has been written, the processor also updates this field with the
address of the next PEBS record to be written. The figure above illustrates the state of PEBS Index after the
first PEBS record is written.
•
PEBS Absolute Maximum: This field represents the absolute address of the maximum length of the allocated
PEBS buffer plus the starting address of the PEBS buffer. The processor will not write any PEBS record beyond
the end of PEBS buffer, when PEBS Index equals PEBS Absolute Maximum. No signaling is generated when
PEBS buffer is full. Software must reset the PEBS Index field to the beginning of the PEBS buffer address to
continue capturing PEBS records.
Vol. 3B 18-37
PERFORMANCE MONITORING
IA32_DS_AREA MSR
DS Buffer Management Area
BTS Buffer Base
0H
BTS Index
8H
BTS Buffer
Branch Record 0
BTS Absolute
Maximum
BTS Interrupt
Threshold
10H
Branch Record 1
18H
PEBS Buffer Base 20H
PEBS Index
PEBS Absolute
Maximum
PEBS Interrupt
Threshold
PEBS
Counter0 Reset
PEBS
Counter1 Reset
PEBS
Counter2 Reset
PEBS
Counter3 Reset
Reserved
28H
30H
Branch Record n
38H
40H
PEBS Buffer
48H
PEBS Record 0
50H
PEBS Record 1
58H
60H
PEBS Record n
Figure 18-22. PEBS Programming Environment
•
PEBS Interrupt Threshold: This field specifies the threshold value to trigger a performance interrupt and
notify software that the PEBS buffer is nearly full. This field is programmed with the linear address of the first
byte of the PEBS record within the PEBS buffer that represents the threshold record. After the processor writes
a PEBS record and updates PEBS Index, if the PEBS Index reaches the threshold value of this field, the
processor will generate a performance interrupt. This is the same interrupt that is generated by a performance
counter overflow, as programmed in the Performance Monitoring Counters vector in the Local Vector Table of
the Local APIC. When a performance interrupt due to PEBS buffer full is generated, the
IA32_PERF_GLOBAL_STATUS.PEBS_Ovf bit will be set.
•
PEBS CounterX Reset: This field allows software to set up PEBS counter overflow condition to occur at a rate
useful for profiling workload, thereby generating multiple PEBS records to facilitate characterizing the profile
the execution of test code. After each PEBS record is written, the processor checks each counter to see if it
overflowed and was enabled for PEBS (the corresponding bit in IA32_PEBS_ENABLED was set). If these
conditions are met, then the reset value for each overflowed counter is loaded from the DS Buffer Management
Area. For example, if counter IA32_PMC0 caused a PEBS record to be written, then the value of “PEBS Counter
0 Reset” would be written to counter IA32_PMC0. If a counter is not enabled for PEBS, its value will not be
modified by the PEBS assist.
Performance Counter Prioritization
Performance monitoring interrupts are triggered by a counter transitioning from maximum count to zero (assuming
IA32_PerfEvtSelX.INT is set). This same transition will cause PEBS hardware to arm, but not trigger. PEBS hardware triggers upon detection of the first PEBS event after the PEBS hardware has been armed (a 0 to 1 transition
of the counter). At this point, a PEBS assist will be undertaken by the processor.
18-38 Vol. 3B
PERFORMANCE MONITORING
Performance counters (fixed and general-purpose) are prioritized in index order. That is, counter IA32_PMC0 takes
precedence over all other counters. Counter IA32_PMC1 takes precedence over counters IA32_PMC2 and
IA32_PMC3, and so on. This means that if simultaneous overflows or PEBS assists occur, the appropriate action will
be taken for the highest priority performance counter. For example, if IA32_PMC1 cause an overflow interrupt and
IA32_PMC2 causes an PEBS assist simultaneously, then the overflow interrupt will be serviced first.
The PEBS threshold interrupt is triggered by the PEBS assist, and is by definition prioritized lower than the PEBS
assist. Hardware will not generate separate interrupts for each counter that simultaneously overflows. Generalpurpose performance counters are prioritized over fixed counters.
If a counter is programmed with a precise (PEBS-enabled) event and programmed to generate a counter overflow
interrupt, the PEBS assist is serviced before the counter overflow interrupt is serviced. If in addition the PEBS interrupt threshold is met, the
threshold interrupt is generated after the PEBS assist completes, followed by the counter overflow interrupt (two
separate interrupts are generated).
Uncore counters may be programmed to interrupt one or more processor cores (see Section 18.8.2). It is possible
for interrupts posted from the uncore facility to occur coincident with counter overflow interrupts from the
processor core. Software must check core and uncore status registers to determine the exact origin of counter
overflow interrupts.
18.8.1.2
Load Latency Performance Monitoring Facility
The load latency facility provides software a means to characterize the average load latency to different levels of
cache/memory hierarchy. This facility requires processor supporting enhanced PEBS record format in the PEBS
buffer, see Table 18-23. This field measures the load latency from load's first dispatch of till final data writeback
from the memory subsystem. The latency is reported for retired demand load operations and in core cycles (it
accounts for re-dispatches).
To use this feature software must assure:
•
One of the IA32_PERFEVTSELx MSR is programmed to specify the event unit MEM_INST_RETIRED, and the
LATENCY_ABOVE_THRESHOLD event mask must be specified (IA32_PerfEvtSelX[15:0] = 100H). The corresponding counter IA32_PMCx will accumulate event counts for architecturally visible loads which exceed the
programmed latency threshold specified separately in a MSR. Stores are ignored when this event is
programmed. The CMASK or INV fields of the IA32_PerfEvtSelX register used for counting load latency must be
0. Writing other values will result in undefined behavior.
•
The MSR_PEBS_LD_LAT_THRESHOLD MSR is programmed with the desired latency threshold in core clock
cycles. Loads with latencies greater than this value are eligible for counting and latency data reporting. The
minimum value that may be programmed in this register is 3 (the minimum detectable load latency is 4 core
clock cycles).
•
The PEBS enable bit in the IA32_PEBS_ENABLE register is set for the corresponding IA32_PMCx counter
register. This means that both the PEBS_EN_CTRX and LL_EN_CTRX bits must be set for the counter(s) of
interest. For example, to enable load latency on counter IA32_PMC0, the IA32_PEBS_ENABLE register must be
programmed with the 64-bit value 00000001_00000001H.
When the load-latency facility is enabled, load operations are randomly selected by hardware and tagged to carry
information related to data source locality and latency. Latency and data source information of tagged loads are
updated internally.
When a PEBS assist occurs, the last update of latency and data source information are captured by the assist and
written as part of the PEBS record. The PEBS sample after value (SAV), specified in PEBS CounterX Reset, operates
orthogonally to the tagging mechanism. Loads are randomly tagged to collect latency data. The SAV controls the
number of tagged loads with latency information that will be written into the PEBS record field by the PEBS assists.
The load latency data written to the PEBS record will be for the last tagged load operation which retired just before
the PEBS assist was invoked.
The load-latency information written into a PEBS record (see Table 18-23, bytes AFH:98H) consists of:
•
•
Data Linear Address: This is the linear address of the target of the load operation.
Latency Value: This is the elapsed cycles of the tagged load operation between dispatch to GO, measured in
processor core clock domain.
Vol. 3B 18-39
PERFORMANCE MONITORING
•
Data Source: The encoded value indicates the origin of the data obtained by the load instruction. The encoding
is shown in Table 18-24. In the descriptions local memory refers to system memory physically attached to a
processor package, and remote memory referrals to system memory physically attached to another processor
package.
Table 18-24. Data Source Encoding for Load Latency Record
Encoding
Description
00H
Unknown L3 cache miss
01H
Minimal latency core cache hit. This request was satisfied by the L1 data cache.
02H
Pending core cache HIT. Outstanding core cache miss to same cache-line address was already underway.
03H
This data request was satisfied by the L2.
04H
L3 HIT. Local or Remote home requests that hit L3 cache in the uncore with no coherency actions required (snooping).
05H
L3 HIT. Local or Remote home requests that hit the L3 cache and was serviced by another processor core with a cross
core snoop where no modified copies were found. (clean).
06H
L3 HIT. Local or Remote home requests that hit the L3 cache and was serviced by another processor core with a cross
core snoop where modified copies were found. (HITM).
07H1
Reserved/LLC Snoop HitM. Local or Remote home requests that hit the last level cache and was serviced by another
core with a cross core snoop where modified copies found
08H
L3 MISS. Local homed requests that missed the L3 cache and was serviced by forwarded data following a cross
package snoop where no modified copies found. (Remote home requests are not counted).
09H
Reserved
0AH
L3 MISS. Local home requests that missed the L3 cache and was serviced by local DRAM (go to shared state).
0BH
L3 MISS. Remote home requests that missed the L3 cache and was serviced by remote DRAM (go to shared state).
0CH
L3 MISS. Local home requests that missed the L3 cache and was serviced by local DRAM (go to exclusive state).
0DH
L3 MISS. Remote home requests that missed the L3 cache and was serviced by remote DRAM (go to exclusive state).
0EH
I/O, Request of input/output operation
0FH
The request was to un-cacheable memory.
NOTES:
1. Bit 7 is supported only for processor with CPUID DisplayFamily_DisplayModel signature of 06_2A, and 06_2E; otherwise it is
reserved.
The layout of MSR_PEBS_LD_LAT_THRESHOLD is shown in Figure 18-23.
63
1615
0
THRHLD - Load latency threshold
Reserved
RESET Value — 00000000_00000000H
Figure 18-23. Layout of MSR_PEBS_LD_LAT MSR
Bits 15:0 specifies the threshold load latency in core clock cycles. Performance events with latencies greater than
this value are counted in IA32_PMCx and their latency information is reported in the PEBS record. Otherwise, they
are ignored. The minimum value that may be programmed in this field is 3.
18-40 Vol. 3B
PERFORMANCE MONITORING
18.8.1.3
Off-core Response Performance Monitoring in the Processor Core
Programming a performance event using the off-core response facility can choose any of the four
IA32_PERFEVTSELx MSR with specific event codes and predefine mask bit value. Each event code for off-core
response monitoring requires programming an associated configuration MSR, MSR_OFFCORE_RSP_0. There is
only one off-core response configuration MSR. Table 18-25 lists the event code, mask value and additional off-core
configuration MSR that must be programmed to count off-core response events using IA32_PMCx.
Table 18-25. Off-Core Response Event Encoding
Event code in
IA32_PERFEVTSELx
Mask Value in
IA32_PERFEVTSELx
Required Off-core Response MSR
B7H
01H
MSR_OFFCORE_RSP_0 (address 1A6H)
The layout of MSR_OFFCORE_RSP_0 is shown in Figure 18-24. Bits 7:0 specifies the request type of a transaction
request to the uncore. Bits 15:8 specifies the response of the uncore subsystem.
63
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
RESPONSE TYPE — NON_DRAM (R/W)
RESPONSE TYPE — LOCAL_DRAM (R/W)
RESPONSE TYPE — REMOTE_DRAM (R/W)
RESPONSE TYPE — REMOTE_CACHE_FWD (R/W)
RESPONSE TYPE — RESERVED
RESPONSE TYPE — OTHER_CORE_HITM (R/W)
RESPONSE TYPE — OTHER_CORE_HIT_SNP (R/W)
RESPONSE TYPE — UNCORE_HIT (R/W)
REQUEST TYPE — OTHER (R/W)
REQUEST TYPE — PF_IFETCH (R/W)
REQUEST TYPE — PF_RFO (R/W)
REQUEST TYPE — PF_DATA_RD (R/W)
REQUEST TYPE — WB (R/W)
REQUEST TYPE — DMND_IFETCH (R/W)
REQUEST TYPE — DMND_RFO (R/W)
REQUEST TYPE — DMND_DATA_RD (R/W)
Reserved
RESET Value — 00000000_00000000H
Figure 18-24. Layout of MSR_OFFCORE_RSP_0 and MSR_OFFCORE_RSP_1 to Configure Off-core Response Events
Table 18-26. MSR_OFFCORE_RSP_0 and MSR_OFFCORE_RSP_1 Bit Field Definition
Bit Name
Offset
Description
DMND_DATA_RD
0
(R/W). Counts the number of demand and DCU prefetch data reads of full and partial cachelines as well
as demand data page table entry cacheline reads. Does not count L2 data read prefetches or
instruction fetches.
DMND_RFO
1
(R/W). Counts the number of demand and DCU prefetch reads for ownership (RFO) requests generated
by a write to data cacheline. Does not count L2 RFO.
DMND_IFETCH
2
(R/W). Counts the number of demand and DCU prefetch instruction cacheline reads. Does not count L2
code read prefetches.
WB
3
(R/W). Counts the number of writeback (modified to exclusive) transactions.
PF_DATA_RD
4
(R/W). Counts the number of data cacheline reads generated by L2 prefetchers.
PF_RFO
5
(R/W). Counts the number of RFO requests generated by L2 prefetchers.
Vol. 3B 18-41
PERFORMANCE MONITORING
Table 18-26. MSR_OFFCORE_RSP_0 and MSR_OFFCORE_RSP_1 Bit Field Definition (Contd.)
Bit Name
Offset
Description
PF_IFETCH
6
(R/W). Counts the number of code reads generated by L2 prefetchers.
OTHER
7
(R/W). Counts one of the following transaction types, including L3 invalidate, I/O, full or partial writes,
WC or non-temporal stores, CLFLUSH, Fences, lock, unlock, split lock.
UNCORE_HIT
8
(R/W). L3 Hit: local or remote home requests that hit L3 cache in the uncore with no coherency actions
required (snooping).
OTHER_CORE_HI
T_SNP
9
(R/W). L3 Hit: local or remote home requests that hit L3 cache in the uncore and was serviced by
another core with a cross core snoop where no modified copies were found (clean).
OTHER_CORE_HI
TM
10
(R/W). L3 Hit: local or remote home requests that hit L3 cache in the uncore and was serviced by
another core with a cross core snoop where modified copies were found (HITM).
Reserved
11
Reserved
REMOTE_CACHE_ 12
FWD
(R/W). L3 Miss: local homed requests that missed the L3 cache and was serviced by forwarded data
following a cross package snoop where no modified copies found. (Remote home requests are not
counted)
REMOTE_DRAM
13
(R/W). L3 Miss: remote home requests that missed the L3 cache and were serviced by remote DRAM.
LOCAL_DRAM
14
(R/W). L3 Miss: local home requests that missed the L3 cache and were serviced by local DRAM.
NON_DRAM
15
(R/W). Non-DRAM requests that were serviced by IOH.
18.8.2
Performance Monitoring Facility in the Uncore
The “uncore” in Intel microarchitecture code name Nehalem refers to subsystems in the physical processor
package that are shared by multiple processor cores. Some of the sub-systems in the uncore include the L3 cache,
Intel QuickPath Interconnect link logic, and integrated memory controller. The performance monitoring facilities
inside the uncore operates in the same clock domain as the uncore (U-clock domain), which is usually different
from the processor core clock domain. The uncore performance monitoring facilities described in this section apply
to Intel Xeon processor 5500 series and processors with the following CPUID signatures: 06_1AH, 06_1EH, 06_1FH
(see Chapter 35). An overview of the uncore performance monitoring facilities is described separately.
The performance monitoring facilities available in the U-clock domain consist of:
•
Eight General-purpose counters (MSR_UNCORE_PerfCntr0 through MSR_UNCORE_PerfCntr7). The counters
are 48 bits wide. Each counter is associated with a configuration MSR, MSR_UNCORE_PerfEvtSelx, to specify
event code, event mask and other event qualification fields. A set of global uncore performance counter
enabling/overflow/status control MSRs are also provided for software.
•
Performance monitoring in the uncore provides an address/opcode match MSR that provides event qualification
control based on address value or QPI command opcode.
•
One fixed-function counter, MSR_UNCORE_FixedCntr0. The fixed-function uncore counter increments at the
rate of the U-clock when enabled.
The frequency of the uncore clock domain can be determined from the uncore clock ratio which is available in
the PCI configuration space register at offset C0H under device number 0 and Function 0.
18.8.2.1
Uncore Performance Monitoring Management Facility
MSR_UNCORE_PERF_GLOBAL_CTRL provides bit fields to enable/disable general-purpose and fixed-function counters in the uncore. Figure 18-25 shows the layout of MSR_UNCORE_PERF_GLOBAL_CTRL for an uncore that is
shared by four processor cores in a physical package.
•
EN_PCn (bit n, n = 0, 7): When set, enables counting for the general-purpose uncore counter
MSR_UNCORE_PerfCntr n.
•
EN_FC0 (bit 32): When set, enables counting for the fixed-function uncore counter MSR_UNCORE_FixedCntr0.
18-42 Vol. 3B
PERFORMANCE MONITORING
•
EN_PMI_COREn (bit n, n = 0, 3 if four cores are present): When set, processor core n is programmed to receive
an interrupt signal from any interrupt enabled uncore counter. PMI delivery due to an uncore counter overflow
is enabled by setting IA32_DEBUGCTL.Offcore_PMI_EN to 1.
•
PMI_FRZ (bit 63): When set, all U-clock uncore counters are disabled when any one of them signals a
performance interrupt. Software must explicitly re-enable the counter by setting the enable bits in
MSR_UNCORE_PERF_GLOBAL_CTRL upon exit from the ISR.
63 62
51 50 49 48
32 31
8 7 6 5 43 2 1 0
PMI_FRZ (R/W)
EN_PMI_CORE3 (R/W)
EN_PMI_CORE2 (R/W)
EN_PMI_CORE1 (R/W)
EN_PMI_CORE0 (R/W)
EN_FC0 (R/W)
EN_PC7 (R/W)
EN_PC6 (R/W)
EN_PC5 (R/W)
EN_PC4 (R/W)
EN_PC3 (R/W)
EN_PC2 (R/W)
EN_PC1 (R/W)
EN_PC0 (R/W)
Reserved
RESET Value — 00000000_00000000H
Figure 18-25. Layout of MSR_UNCORE_PERF_GLOBAL_CTRL MSR
MSR_UNCORE_PERF_GLOBAL_STATUS provides overflow status of the U-clock performance counters in the
uncore. This is a read-only register. If an overflow status bit is set the corresponding counter has overflowed. The
register provides a condition change bit (bit 63) which can be quickly checked by software to determine if a significant change has occurred since the last time the condition change status was cleared. Figure 18-26 shows the
layout of MSR_UNCORE_PERF_GLOBAL_STATUS.
•
OVF_PCn (bit n, n = 0, 7): When set, indicates general-purpose uncore counter MSR_UNCORE_PerfCntr n has
overflowed.
•
OVF_FC0 (bit 32): When set, indicates the fixed-function uncore counter MSR_UNCORE_FixedCntr0 has
overflowed.
•
•
OVF_PMI (bit 61): When set indicates that an uncore counter overflowed and generated an interrupt request.
CHG (bit 63): When set indicates that at least one status bit in MSR_UNCORE_PERF_GLOBAL_STATUS register
has changed state.
MSR_UNCORE_PERF_GLOBAL_OVF_CTRL allows software to clear the status bits in the
UNCORE_PERF_GLOBAL_STATUS register. This is a write-only register, and individual status bits in the global
status register are cleared by writing a binary one to the corresponding bit in this register. Writing zero to any bit
position in this register has no effect on the uncore PMU hardware.
Vol. 3B 18-43
PERFORMANCE MONITORING
63 62 61 60
32 31
8 7 6 5 43 2 1 0
CHG (R/W)
OVF_PMI (R/W)
OVF_FC0 (R/O)
OVF_PC7 (R/O)
OVF_PC6 (R/O)
OVF_PC5 (R/O)
OVF_PC4 (R/O)
OVF_PC3 (R/O)
OVF_PC2 (R/O)
OVF_PC1 (R/O)
OVF_PC0 (R/O)
Reserved
RESET Value — 00000000_00000000H
Figure 18-26. Layout of MSR_UNCORE_PERF_GLOBAL_STATUS MSR
Figure 18-27 shows the layout of MSR_UNCORE_PERF_GLOBAL_OVF_CTRL.
63 62 61 60
32 31
8 7 6 5 43 2 1 0
CLR_CHG (WO1)
CLR_OVF_PMI (WO1)
CLR_OVF_FC0 (WO1)
CLR_OVF_PC7 (WO1)
CLR_OVF_PC6 (WO1)
CLR_OVF_PC5 (WO1)
CLR_OVF_PC4 (WO1)
CLR_OVF_PC3 (WO1)
CLR_OVF_PC2 (WO1)
CLR_OVF_PC1 (WO1)
CLR_OVF_PC0 (WO1)
Reserved
RESET Value — 00000000_00000000H
Figure 18-27. Layout of MSR_UNCORE_PERF_GLOBAL_OVF_CTRL MSR
•
CLR_OVF_PCn (bit n, n = 0, 7): Set this bit to clear the overflow status for general-purpose uncore counter
MSR_UNCORE_PerfCntr n. Writing a value other than 1 is ignored.
•
CLR_OVF_FC0 (bit 32): Set this bit to clear the overflow status for the fixed-function uncore counter
MSR_UNCORE_FixedCntr0. Writing a value other than 1 is ignored.
•
CLR_OVF_PMI (bit 61): Set this bit to clear the OVF_PMI flag in MSR_UNCORE_PERF_GLOBAL_STATUS. Writing
a value other than 1 is ignored.
•
CLR_CHG (bit 63): Set this bit to clear the CHG flag in MSR_UNCORE_PERF_GLOBAL_STATUS register. Writing
a value other than 1 is ignored.
18-44 Vol. 3B
PERFORMANCE MONITORING
18.8.2.2
Uncore Performance Event Configuration Facility
MSR_UNCORE_PerfEvtSel0 through MSR_UNCORE_PerfEvtSel7 are used to select performance event and
configure the counting behavior of the respective uncore performance counter. Each uncore PerfEvtSel MSR is
paired with an uncore performance counter. Each uncore counter must be locally configured using the corresponding MSR_UNCORE_PerfEvtSelx and counting must be enabled using the respective EN_PCx bit in
MSR_UNCORE_PERF_GLOBAL_CTRL. Figure 18-28 shows the layout of MSR_UNCORE_PERFEVTSELx.
63
31
24 23 22 21 20 19 18 17 16 15
Counter Mask
(CMASK)
8 7
Unit Mask (UMASK)
INV—Invert counter mask
EN—Enable counters
PMI—Enable PMI on overflow
E—Edge detect
OCC_CTR_RST—Rest Queue Occ
0
Event Select
Reserved
RESET Value — 00000000_00000000H
Figure 18-28. Layout of MSR_UNCORE_PERFEVTSELx MSRs
•
•
•
Event Select (bits 7:0): Selects the event logic unit used to detect uncore events.
•
Edge Detect (bit 18): When set causes the counter to increment when a deasserted to asserted transition
occurs for the conditions that can be expressed by any of the fields in this register.
•
PMI (bit 20): When set, the uncore will generate an interrupt request when this counter overflowed. This
request will be routed to the logical processors as enabled in the PMI enable bits (EN_PMI_COREx) in the
register MSR_UNCORE_PERF_GLOBAL_CTRL.
•
EN (bit 22): When clear, this counter is locally disabled. When set, this counter is locally enabled and counting
starts when the corresponding EN_PCx bit in MSR_UNCORE_PERF_GLOBAL_CTRL is set.
•
INV (bit 23): When clear, the Counter Mask field is interpreted as greater than or equal to. When set, the
Counter Mask field is interpreted as less than.
•
Counter Mask (bits 31:24): When this field is clear, it has no effect on counting. When set to a value other than
zero, the logical processor compares this field to the event counts on each core clock cycle. If INV is clear and
the event counts are greater than or equal to this field, the counter is incremented by one. If INV is set and the
event counts are less than this field, the counter is incremented by one. Otherwise the counter is not incremented.
Unit Mask (bits 15:8) : Condition qualifiers for the event selection logic specified in the Event Select field.
OCC_CTR_RST (bit17): When set causes the queue occupancy counter associated with this event to be cleared
(zeroed). Writing a zero to this bit will be ignored. It will always read as a zero.
Figure 18-29 shows the layout of MSR_UNCORE_FIXED_CTR_CTRL.
63
8 7 6 5 43 2 1 0
PMI - Generate PMI on overflow
EN - Enable
Reserved
RESET Value — 00000000_00000000H
Figure 18-29. Layout of MSR_UNCORE_FIXED_CTR_CTRL MSR
Vol. 3B 18-45
PERFORMANCE MONITORING
•
EN (bit 0): When clear, the uncore fixed-function counter is locally disabled. When set, it is locally enabled and
counting starts when the EN_FC0 bit in MSR_UNCORE_PERF_GLOBAL_CTRL is set.
•
PMI (bit 2): When set, the uncore will generate an interrupt request when the uncore fixed-function counter
overflowed. This request will be routed to the logical processors as enabled in the PMI enable bits
(EN_PMI_COREx) in the register MSR_UNCORE_PERF_GLOBAL_CTRL.
Both the general-purpose counters (MSR_UNCORE_PerfCntr) and the fixed-function counter
(MSR_UNCORE_FixedCntr0) are 48 bits wide. They support both counting and interrupt based sampling usages.
The event logic unit can filter event counts to specific regions of code or transaction types incoming to the home
node logic.
18.8.2.3
Uncore Address/Opcode Match MSR
The Event Select field [7:0] of MSR_UNCORE_PERFEVTSELx is used to select different uncore event logic unit.
When the event “ADDR_OPCODE_MATCH” is selected in the Event Select field, software can filter uncore performance events according to transaction address and certain transaction responses. The address filter and transaction response filtering requires the use of MSR_UNCORE_ADDR_OPCODE_MATCH register. The layout is shown in
Figure 18-30.
63
60
48 47
40 39
Opcode
3 2 0
ADDR
MatchSel—Select addr/Opcode
Opcode—Opcode and Message
ADDR—Bits 39:4 of physical address
Reserved
RESET Value — 00000000_00000000H
Figure 18-30. Layout of MSR_UNCORE_ADDR_OPCODE_MATCH MSR
•
Addr (bits 39:3): The physical address to match if “MatchSel“ field is set to select address match. The uncore
performance counter will increment if the lowest 40-bit incoming physical address (excluding bits 2:0) for a
transaction request matches bits 39:3.
•
Opcode (bits 47:40) : Bits 47:40 allow software to filter uncore transactions based on QPI link message
class/packed header opcode. These bits are consists two sub-fields:
— Bits 43:40 specify the QPI packet header opcode,
— Bits 47:44 specify the QPI message classes.
Table 18-27 lists the encodings supported in the opcode field.
18-46 Vol. 3B
PERFORMANCE MONITORING
Table 18-27. Opcode Field Encoding for MSR_UNCORE_ADDR_OPCODE_MATCH
Opcode [43:40]
QPI Message Class
Home Request
Snoop Response
Data Response
[47:44] = 0000B
[47:44] = 0001B
[47:44] = 1110B
1
DMND_IFETCH
2
2
WB
3
3
PF_DATA_RD
4
4
PF_RFO
5
5
PF_IFETCH
6
6
OTHER
7
7
NON_DRAM
15
15
•
MatchSel (bits 63:61): Software specifies the match criteria according to the following encoding:
— 000B: Disable addr_opcode match hardware
— 100B: Count if only the address field matches,
— 010B: Count if only the opcode field matches
— 110B: Count if either opcode field matches or the address field matches
— 001B: Count only if both opcode and address field match
— Other encoding are reserved
18.8.3
Intel® Xeon® Processor 7500 Series Performance Monitoring Facility
The performance monitoring facility in the processor core of Intel® Xeon® processor 7500 series are the same as
those supported in Intel Xeon processor 5500 series. The uncore subsystem in Intel Xeon processor 7500 series
are significantly different The uncore performance monitoring facility consist of many distributed units associated
with individual logic control units (referred to as boxes) within the uncore subsystem. A high level block diagram of
the various box units of the uncore is shown in Figure 18-31.
Uncore PMUs are programmed via MSR interfaces. Each of the distributed uncore PMU units have several generalpurpose counters. Each counter requires an associated event select MSR, and may require additional MSRs to
configure sub-event conditions. The uncore PMU MSRs associated with each box can be categorized based on its
functional scope: per-counter, per-box, or global across the uncore. The number counters available in each box
type are different. Each box generally provides a set of MSRs to enable/disable, check status/overflow of multiple
counters within each box.
Vol. 3B 18-47
PERFORMANCE MONITORING
L3 Cache
CBox
CBox
CBox
CBox
CBox
SBox
CBox
CBox
CBox
SBox
SMI Channels
PBox
MBox
BBox
RBox
BBox
MBox
PBox
SMI Channels
WBox
PBox
PBox
PBox
PBox
UBox
4 Intel QPI Links
Figure 18-31. Distributed Units of the Uncore of Intel® Xeon® Processor 7500 Series
Table 18-28 summarizes the number MSRs for uncore PMU for each box.
Table 18-28. Uncore PMU MSR Summary
Box
# of Boxes
Counters per Box
Counter
Width
General
Purpose
Global
Enable
Sub-control MSRs
C-Box
8
6
48
Yes
per-box
None
S-Box
2
4
48
Yes
per-box
Match/Mask
B-Box
2
4
48
Yes
per-box
Match/Mask
M-Box
2
6
48
Yes
per-box
Yes
R-Box
1
16 ( 2 port, 8 per port)
48
Yes
per-box
Yes
W-Box
1
4
48
Yes
per-box
None
1
48
No
per-box
None
1
48
Yes
uncore
None
U-Box
1
The W-Box provides 4 general-purpose counters, each requiring an event select configuration MSR, similar to the
general-purpose counters in other boxes. There is also a fixed-function counter that increments clockticks in the
uncore clock domain.
For C,S,B,M,R, and W boxes, each box provides an MSR to enable/disable counting, configuring PMI of multiple
counters within the same box, this is somewhat similar the “global control“ programming interface,
IA32_PERF_GLOBAL_CTRL, offered in the core PMU. Similarly status information and counter overflow control for
multiple counters within the same box are also provided in C,S,B,M,R, and W boxes.
In the U-Box, MSR_U_PMON_GLOBAL_CTL provides overall uncore PMU enable/disable and PMI configuration
control. The scope of status information in the U-box is at per-box granularity, in contrast to the per-box status
information MSR (in the C,S,B,M,R, and W boxes) providing status information of individual counter overflow. The
difference in scope also apply to the overflow control MSR in the U-Box versus those in the other Boxes.
18-48 Vol. 3B
PERFORMANCE MONITORING
The individual MSRs that provide uncore PMU interfaces are listed in Chapter 35, Table 35-15 under the general
naming style of MSR_%box#%_PMON_%scope_function%, where %box#% designates the type of box and zerobased index if there are more the one box of the same type, %scope_function% follows the examples below:
•
Multi-counter enabling MSRs: MSR_U_PMON_GLOBAL_CTL, MSR_S0_PMON_BOX_CTL,
MSR_C7_PMON_BOX_CTL, etc.
•
Multi-counter status MSRs: MSR_U_PMON_GLOBAL_STATUS, MSR_S0_PMON_BOX_STATUS,
MSR_C7_PMON_BOX_STATUS, etc.
•
Multi-counter overflow control MSRs: MSR_U_PMON_GLOBAL_OVF_CTL, MSR_S0_PMON_BOX_OVF_CTL,
MSR_C7_PMON_BOX_OVF_CTL, etc.
•
Performance counters MSRs: the scope is implicitly per counter, e.g. MSR_U_PMON_CTR,
MSR_S0_PMON_CTR0, MSR_C7_PMON_CTR5, etc.
•
Event select MSRs: the scope is implicitly per counter, e.g. MSR_U_PMON_EVNT_SEL,
MSR_S0_PMON_EVNT_SEL0, MSR_C7_PMON_EVNT_SEL5, etc
•
Sub-control MSRs: the scope is implicitly per-box granularity, e.g. MSR_M0_PMON_TIMESTAMP,
MSR_R0_PMON_IPERF0_P1, MSR_S1_PMON_MATCH.
Details of uncore PMU MSR bit field definitions can be found in a separate document “Intel Xeon Processor 7500
Series Uncore Performance Monitoring Guide“.
18.8.4
Performance Monitoring for Processors Based on Intel® Microarchitecture Code Name
Westmere
All of the performance monitoring programming interfaces (architectural and non-architectural core PMU facilities,
and uncore PMU) described in Section 18.8 also apply to processors based on Intel® microarchitecture code name
Westmere.
Table 18-25 describes a non-architectural performance monitoring event (event code 0B7H) and associated
MSR_OFFCORE_RSP_0 (address 1A6H) in the core PMU. This event and a second functionally equivalent offcore
response event using event code 0BBH and MSR_OFFCORE_RSP_1 (address 1A7H) are supported in processors
based on Intel microarchitecture code name Westmere. The event code and event mask definitions of Non-architectural performance monitoring events are listed in Table 19-26.
The load latency facility is the same as described in Section 18.8.1.2, but added enhancement to provide more
information in the data source encoding field of each load latency record. The additional information relates to
STLB_MISS and LOCK, see Table 18-33.
18.8.5
Intel® Xeon® Processor E7 Family Performance Monitoring Facility
The performance monitoring facility in the processor core of the Intel® Xeon® processor E7 family is the same as
those supported in the Intel Xeon processor 5600 series3. The uncore subsystem in the Intel Xeon processor E7
family is similar to those of the Intel Xeon processor 7500 series. The high level construction of the uncore subsystem is similar to that shown in Figure 18-31, with the additional capability that up to 10 C-Box units are
supported.
Table 18-29 summarizes the number MSRs for uncore PMU for each box.
Table 18-29. Uncore PMU MSR Summary for Intel® Xeon® Processor E7 Family
Box
# of Boxes
Counters per Box
Counter
Width
General
Purpose
Global
Enable
Sub-control MSRs
C-Box
10
6
48
Yes
per-box
None
S-Box
2
4
48
Yes
per-box
Match/Mask
3. Exceptions are indicated for event code 0FH in Table 19-19; and valid bits of data source encoding field of each load
latency record is limited to bits 5:4 of Table 18-33.
Vol. 3B 18-49
PERFORMANCE MONITORING
Table 18-29. Uncore PMU MSR Summary for Intel® Xeon® Processor E7 Family
Box
# of Boxes
Counters per Box
Counter
Width
General
Purpose
Global
Enable
Sub-control MSRs
B-Box
2
4
48
Yes
per-box
Match/Mask
M-Box
2
6
48
Yes
per-box
Yes
R-Box
1
16 ( 2 port, 8 per port)
48
Yes
per-box
Yes
W-Box
1
4
48
Yes
per-box
None
1
48
No
per-box
None
1
48
Yes
uncore
None
U-Box
1
Details of the uncore performance monitoring facility of Intel Xeon Processor E7 family is available in the “Intel®
Xeon® Processor E7 Uncore Performance Monitoring Programming Reference Manual”.
18.9
PERFORMANCE MONITORING FOR PROCESSORS BASED ON INTEL®
MICROARCHITECTURE CODE NAME SANDY BRIDGE
Intel® Core™ i7-2xxx, Intel® Core™ i5-2xxx, Intel® Core™ i3-2xxx processor series, and Intel® Xeon® processor
E3-1200 family are based on Intel microarchitecture code name Sandy Bridge; this section describes the performance monitoring facilities provided in the processor core. The core PMU supports architectural performance monitoring capability with version ID 3 (see Section 18.2.3) and a host of non-architectural monitoring capabilities.
Architectural performance monitoring version 3 capabilities are described in Section 18.2.3.
The core PMU’s capability is similar to those described in Section 18.8.1 and Section 18.8.4, with some differences
and enhancements relative to Intel microarchitecture code name Westmere summarized in Table 18-30.
Table 18-30. Core PMU Comparison
Intel® microarchitecture code
name Sandy Bridge
Intel® microarchitecture code
name Westmere
# of Fixed counters per
thread
3
3
# of general-purpose
counters per core
8
8
Counter width (R,W)
R:48, W: 32/48
R:48, W:32
See Section 18.2.2.
# of programmable counters
per thread
4 or (8 if a core not shared by two
threads)
4
Use CPUID to enumerate # of
counters.
PMI Overhead Mitigation
• Freeze_Perfmon_on_PMI with
legacy semantics.
• Freeze_on_LBR with legacy
semantics for branch profiling.
• Freeze_while_SMM.
• Freeze_Perfmon_on_PMI
with legacy semantics.
• Freeze_on_LBR with legacy
semantics for branch
profiling.
• Freeze_while_SMM.
See Section 17.4.7.
Processor Event Based
Sampling (PEBS) Events
See Table 18-32.
See Table 18-10.
IA32_PMC4-IA32_PMC7 do
not support PEBS.
PEBS-Load Latency
See Section 18.9.4.2;
Data source encoding
Box
• Data source encoding
• STLB miss encoding
• Lock transaction encoding
PEBS-Precise Store
18-50 Vol. 3B
Section 18.9.4.3
No
Comment
Use CPUID to enumerate # of
counters.
PERFORMANCE MONITORING
Table 18-30. Core PMU Comparison (Contd.)
Intel® microarchitecture code
name Sandy Bridge
Intel® microarchitecture code
name Westmere
PEBS-PDIR
Yes (using precise
INST_RETIRED.ALL).
No
Off-core Response Event
MSR 1A6H and 1A7H, extended
request and response types.
MSR 1A6H and 1A7H, limited
response types.
Box
18.9.1
Comment
Nehalem supports 1A6H
only.
Global Counter Control Facilities In Intel® Microarchitecture Code Name Sandy Bridge
The number of general-purpose performance counters visible to a logical processor can vary across Processors
based on Intel microarchitecture code name Sandy Bridge. Software must use CPUID to determine the number
performance counters/event select registers (See Section 18.2.1.1).
63
35 34 33 32 31
8 7 6 5 4 3 2 10
FIXED_CTR2 enable
FIXED_CTR1 enable
FIXED_CTR0 enable
PMC7_EN (if PMC7 present)
PMC6_EN (if PMC6 present)
PMC5_EN (if PMC5 present)
PMC4_EN (if PMC4 present)
PMC3_EN
PMC2_EN
PMC1_EN
PMC0_EN
Reserved
Valid if CPUID.0AH:EAX[15:8] = 8, else reserved.
Figure 18-32. IA32_PERF_GLOBAL_CTRL MSR in Intel® Microarchitecture Code Name Sandy Bridge
Figure 18-15 depicts the layout of IA32_PERF_GLOBAL_CTRL MSR. The enable bits (PMC4_EN, PMC5_EN,
PMC6_EN, PMC7_EN) corresponding to IA32_PMC4-IA32_PMC7 are valid only if CPUID.0AH:EAX[15:8] reports a
value of ‘8’. If CPUID.0AH:EAX[15:8] = 4, attempts to set the invalid bits will cause #GP.
Each enable bit in IA32_PERF_GLOBAL_CTRL is AND’ed with the enable bits for all privilege levels in the respective
IA32_PERFEVTSELx or IA32_PERF_FIXED_CTR_CTRL MSRs to start/stop the counting of respective counters.
Counting is enabled if the AND’ed results is true; counting is disabled when the result is false.
IA32_PERF_GLOBAL_STATUS MSR provides single-bit status used by software to query the overflow condition of
each performance counter. IA32_PERF_GLOBAL_STATUS[bit 62] indicates overflow conditions of the DS area data
buffer (see Figure 18-33). A value of 1 in each bit of the PMCx_OVF field indicates an overflow condition has
occurred in the associated counter.
Vol. 3B 18-51
PERFORMANCE MONITORING
63 62 61
35 34 33 32 31
8 7 6 5 4 3 2 1 0
CondChgd
Ovf_DSBuffer
Ovf_UncorePMU
FIXED_CTR2 Overflow (RO)
FIXED_CTR1 Overflow (RO)
FIXED_CTR0 Overflow (RO)
PMC7_OVF (RO, If PMC7 present)
PMC6_OVF (RO, If PMC6 present)
PMC5_OVF (RO, If PMC5 present)
PMC4_OVF (RO, If PMC4 present)
PMC3_OVF (RO)
PMC2_OVF (RO)
PMC1_OVF (RO)
PMC0_OVF (RO)
Valid if CPUID.0AH:EAX[15:8] = 8; else reserved
Reserved
Figure 18-33. IA32_PERF_GLOBAL_STATUS MSR in Intel® Microarchitecture Code Name Sandy Bridge
When a performance counter is configured for PEBS, an overflow condition in the counter will arm PEBS. On the
subsequent event following overflow, the processor will generate a PEBS event. On a PEBS event, the processor will
perform bounds checks based on the parameters defined in the DS Save Area (see Section 17.4.9). Upon
successful bounds checks, the processor will store the data record in the defined buffer area, clear the counter
overflow status, and reload the counter. If the bounds checks fail, the PEBS will be skipped entirely. In the event
that the PEBS buffer fills up, the processor will set the OvfBuffer bit in MSR_PERF_GLOBAL_STATUS.
IA32_PERF_GLOBAL_OVF_CTL MSR allows software to clear overflow the indicators for general-purpose or fixedfunction counters via a single WRMSR (see Figure 18-34). Clear overflow indications when:
•
•
•
Setting up new values in the event select and/or UMASK field for counting or interrupt based sampling
Reloading counter values to continue sampling
Disabling event counting or interrupt based sampling
63 62
35 34 33 32 31
8 7 6 5 4 3
2 1 0
ClrCondChgd
ClrOvfDSBuffer
ClrOvfUncore
FIXED_CTR2 ClrOverflow
FIXED_CTR1 ClrOverflow
FIXED_CTR0 ClrOverflow
PMC7_ClrOvf (if PMC7 present)
PMC6_ClrOvf (if PMC6 present)
PMC5_ClrOvf (if PMC5 present)
PMC4_ClrOvf (if PMC4 present)
PMC3_ClrOvf
PMC2_ClrOvf
PMC1_ClrOvf
PMC0_ClrOvf
Reserved
Valid if CPUID.0AH:EAX[15:8] = 8; else reserved
Figure 18-34. IA32_PERF_GLOBAL_OVF_CTRL MSR in Intel microarchitecture code name Sandy Bridge
18-52 Vol. 3B
PERFORMANCE MONITORING
18.9.2
Counter Coalescence
In processors based on Intel microarchitecture code name Sandy Bridge, each processor core implements eight
general-purpose counters. CPUID.0AH:EAX[15:8] will report either 4 or 8 depending specific processor’s product
features.
If a processor core is shared by two logical processors, each logical processors can access 4 counters (IA32_PMC0IA32_PMC3). This is the same as in the prior generation for processors based on Intel microarchitecture code name
Nehalem.
If a processor core is not shared by two logical processors, all eight general-purpose counters are visible, and
CPUID.0AH:EAX[15:8] reports 8. IA32_PMC4-IA32_PMC7 occupy MSR addresses 0C5H through 0C8H. Each
counter is accompanied by an event select MSR (IA32_PERFEVTSEL4-IA32_PERFEVTSEL7).
If CPUID.0AH:EAX[15:8] report 4, access to IA32_PMC4-IA32_PMC7, IA32_PMC4-IA32_PMC7 will cause #GP.
Writing 1’s to bit position 7:4 of IA32_PERF_GLOBAL_CTRL, IA32_PERF_GLOBAL_STATUS, or
IA32_PERF_GLOBAL_OVF_CTL will also cause #GP.
18.9.3
Full Width Writes to Performance Counters
Processors based on Intel microarchitecture code name Sandy Bridge support full-width writes to the generalpurpose counters, IA32_PMCx. Support of full-width writes are enumerated by
IA32_PERF_CAPABILITIES.FW_WRITES[13] (see Section 18.2.4).
The default behavior of IA32_PMCx is unchanged, i.e. WRMSR to IA32_PMCx results in a sign-extended 32-bit
value of the input EAX written into IA32_PMCx. Full-width writes must issue WRMSR to a dedicated alias MSR
address for each IA32_PMCx.
Software must check the presence of full-width write capability and the presence of the alias address
IA32_A_PMCx by testing IA32_PERF_CAPABILITIES[13].
18.9.4
PEBS Support in Intel® Microarchitecture Code Name Sandy Bridge
Processors based on Intel microarchitecture code name Sandy Bridge support PEBS, similar to those offered in
prior generation, with several enhanced features. The key components and differences of PEBS facility relative to
Intel microarchitecture code name Westmere is summarized in Table 18-31.
Table 18-31. PEBS Facility Comparison
Box
Intel® microarchitecture code name
Sandy Bridge
Intel® microarchitecture
code name Westmere
Comment
Valid IA32_PMCx
PMC0-PMC3
PMC0-PMC3
No PEBS on PMC4-PMC7.
PEBS Buffer Programming
Section 18.8.1.1
Section 18.8.1.1
Unchanged
IA32_PEBS_ENABLE
Layout
Figure 18-35
Figure 18-21
PEBS record layout
Physical Layout same as Table 18-23.
Table 18-23
Enhanced fields at offsets 98H,
A0H, A8H.
PEBS Events
See Table 18-32.
See Table 18-10.
IA32_PMC4-IA32_PMC7 do not
support PEBS.
PEBS-Load Latency
See Table 18-33.
Table 18-24
PEBS-Precise Store
Yes; see Section 18.9.4.3.
No
IA32_PMC3 only
PEBS-PDIR
Yes
No
IA32_PMC1 only
PEBS skid from EventingIP
1 (or 2 if micro+macro fusion)
1
SAMPLING Restriction
Small SAV(CountDown) value incur higher overhead than prior
generation.
Vol. 3B 18-53
PERFORMANCE MONITORING
Only IA32_PMC0 through IA32_PMC3 support PEBS.
NOTE
PEBS events are only valid when the following fields of IA32_PERFEVTSELx are all zero: AnyThread,
Edge, Invert, CMask.
In a PMU with PDIR capability, PEBS behavior is unpredictable if IA32_PERFEVTSELx or IA32_PMCx
is changed for a PEBS-enabled counter while an event is being counted. To avoid this, changes to
the programming or value of a PEBS-enabled counter should be performed when the counter is
disabled.
In IA32_PEBS_ENABLE MSR, bit 63 is defined as PS_ENABLE: When set, this enables IA32_PMC3 to capture
precise store information. Only IA32_PMC3 supports the precise store facility. In typical usage of PEBS, the bit
fields in IA32_PEBS_ENABLE are written to when the agent software starts PEBS operation; the enabled bit fields
should be modified only when re-programming another PEBS event or cleared when the agent uses the performance counters for non-PEBS operations.
36 3534 33 32 31
63 62
8 7 6 5 43 2 1 0
PS_EN (R/W)
LL_EN_PMC3 (R/W)
LL_EN_PMC2 (R/W)
LL_EN_PMC1 (R/W)
LL_EN_PMC0 (R/W)
PEBS_EN_PMC3 (R/W)
PEBS_EN_PMC2 (R/W)
PEBS_EN_PMC1 (R/W)
PEBS_EN_PMC0 (R/W)
Reserved
RESET Value — 00000000_00000000H
Figure 18-35. Layout of IA32_PEBS_ENABLE MSR
18.9.4.1
PEBS Record Format
The layout of PEBS records physically identical to those shown in Table 18-23, but the fields at offset 98H, A0H and
A8H have been enhanced to support additional PEBS capabilities.
•
Load/Store Data Linear Address (Offset 98H): This field will contain the linear address of the source of the load,
or linear address of the destination of the store.
•
Data Source /Store Status (Offset A0H):When load latency is enabled, this field will contain three piece of
information (including an encoded value indicating the source which satisfied the load operation). The source
field encodings are detailed in Table 18-24. When precise store is enabled, this field will contain information
indicating the status of the store, as detailed in Table 19.
•
Latency Value/0 (Offset A8H): When load latency is enabled, this field contains the latency in cycles to service
the load. This field is not meaningful when precise store is enabled and will be written to zero in that case. Upon
writing the PEBS record, microcode clears the overflow status bits in the IA32_PERF_GLOBAL_STATUS corresponding to those counters that both overflowed and were enabled in the IA32_PEBS_ENABLE register. The
status bits of other counters remain unaffected.
The number PEBS events has expanded. The list of PEBS events supported in Intel microarchitecture code name
Sandy Bridge is shown in Table 18-32.
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PERFORMANCE MONITORING
Table 18-32. PEBS Performance Events for Intel® Microarchitecture Code Name Sandy Bridge
Event Name
Event Select
Sub-event
UMask
INST_RETIRED
C0H
PREC_DIST
01H1
UOPS_RETIRED
C2H
All
01H
Retire_Slots
02H
Conditional
01H
Near_Call
02H
BR_INST_RETIRED
BR_MISP_RETIRED
MEM_UOPS_RETIRED
MEM_LOAD_UOPS_RETIRED
MEM_LOAD_UOPS_LLC_HIT_RETIRED
C4H
C5H
D0H
D1H
D2H
All_branches
04H
Near_Return
08H
Near_Taken
20H
Conditional
01H
Near_Call
02H
All_branches
04H
Not_Taken
10H
Taken
20H
STLB_MISS_LOADS
11H
STLB_MISS_STORE
12H
LOCK_LOADS
21H
SPLIT_LOADS
41H
SPLIT_STORES
42H
ALL_LOADS
81H
ALL_STORES
82H
L1_Hit
01H
L2_Hit
02H
L3_Hit
04H
Hit_LFB
40H
XSNP_Miss
01H
XSNP_Hit
02H
XSNP_Hitm
04H
XSNP_None
08H
NOTES:
1. Only available on IA32_PMC1.
18.9.4.2
Load Latency Performance Monitoring Facility
The load latency facility in Intel microarchitecture code name Sandy Bridge is similar to that in prior microarchitecture. It provides software a means to characterize the average load latency to different levels of cache/memory
hierarchy. This facility requires processor supporting enhanced PEBS record format in the PEBS buffer, see
Table 18-23 and Section 18.9.4.1. This field measures the load latency from load's first dispatch of till final data
writeback from the memory subsystem. The latency is reported for retired demand load operations and in core
cycles (it accounts for re-dispatches).
To use this feature software must assure:
•
One of the IA32_PERFEVTSELx MSR is programmed to specify the event unit MEM_TRANS_RETIRED, and the
LATENCY_ABOVE_THRESHOLD event mask must be specified (IA32_PerfEvtSelX[15:0] = 1CDH). The corresponding counter IA32_PMCx will accumulate event counts for architecturally visible loads which exceed the
Vol. 3B 18-55
PERFORMANCE MONITORING
programmed latency threshold specified separately in a MSR. Stores are ignored when this event is
programmed. The CMASK or INV fields of the IA32_PerfEvtSelX register used for counting load latency must be
0. Writing other values will result in undefined behavior.
•
The MSR_PEBS_LD_LAT_THRESHOLD MSR is programmed with the desired latency threshold in core clock
cycles. Loads with latencies greater than this value are eligible for counting and latency data reporting. The
minimum value that may be programmed in this register is 3 (the minimum detectable load latency is 4 core
clock cycles).
•
The PEBS enable bit in the IA32_PEBS_ENABLE register is set for the corresponding IA32_PMCx counter
register. This means that both the PEBS_EN_CTRX and LL_EN_CTRX bits must be set for the counter(s) of
interest. For example, to enable load latency on counter IA32_PMC0, the IA32_PEBS_ENABLE register must be
programmed with the 64-bit value 00000001.00000001H.
•
When Load latency event is enabled, no other PEBS event can be configured with other counters.
When the load-latency facility is enabled, load operations are randomly selected by hardware and tagged to carry
information related to data source locality and latency. Latency and data source information of tagged loads are
updated internally. The MEM_TRANS_RETIRED event for load latency counts only tagged retired loads. If a load is
cancelled it will not be counted and the internal state of the load latency facility will not be updated. In this case the
hardware will tag the next available load.
When a PEBS assist occurs, the last update of latency and data source information are captured by the assist and
written as part of the PEBS record. The PEBS sample after value (SAV), specified in PEBS CounterX Reset, operates
orthogonally to the tagging mechanism. Loads are randomly tagged to collect latency data. The SAV controls the
number of tagged loads with latency information that will be written into the PEBS record field by the PEBS assists.
The load latency data written to the PEBS record will be for the last tagged load operation which retired just before
the PEBS assist was invoked.
The physical layout of the PEBS records is the same as shown in Table 18-23. The specificity of Data Source entry
at offset A0H has been enhanced to report three piece of information.
Table 18-33. Layout of Data Source Field of Load Latency Record
Field
Position
Description
Source
3:0
See Table 18-24
STLB_MISS
4
0: The load did not miss the STLB (hit the DTLB or STLB).
1: The load missed the STLB.
Lock
5
0: The load was not part of a locked transaction.
1: The load was part of a locked transaction.
Reserved
63:6
Reserved
The layout of MSR_PEBS_LD_LAT_THRESHOLD is the same as shown in Figure 18-23.
18.9.4.3
Precise Store Facility
Processors based on Intel microarchitecture code name Sandy Bridge offer a precise store capability that complements the load latency facility. It provides a means to profile store memory references in the system.
Precise stores leverage the PEBS facility and provide additional information about sampled stores. Having precise
memory reference events with linear address information for both loads and stores can help programmers improve
data structure layout, eliminate remote node references, and identify cache-line conflicts in NUMA systems.
Only IA32_PMC3 can be used to capture precise store information. After enabling this facility, counter overflows will
initiate the generation of PEBS records as previously described in PEBS. Upon counter overflow hardware captures
the linear address and other status information of the next store that retires. This information is then written to the
PEBS record.
To enable the precise store facility, software must complete the following steps. Please note that the precise store
facility relies on the PEBS facility, so the PEBS configuration requirements must be completed before attempting to
capture precise store information.
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PERFORMANCE MONITORING
•
•
Complete the PEBS configuration steps.
•
Set IA32_PEBS_ENABLE[3] and IA32_PEBS_ENABLE[63]. This enables IA32_PMC3 as a PEBS counter and
enables the precise store facility, respectively.
Program the MEM_TRANS_RETIRED.PRECISE_STORE event in IA32_PERFEVTSEL3. Only counter 3
(IA32_PMC3) supports collection of precise store information.
The precise store information written into a PEBS record affects entries at offset 98H, A0H and A8H of Table 18-23.
The specificity of Data Source entry at offset A0H has been enhanced to report three piece of information.
Table 18-34. Layout of Precise Store Information In PEBS Record
Field
Offset Description
Store Data
98H
Linear Address
The linear address of the destination of the store.
Store Status
L1D Hit (Bit 0): The store hit the data cache closest to the core (lowest latency cache) if this bit is set,
otherwise the store missed the data cache.
A0H
STLB Miss (bit 4): The store missed the STLB if set, otherwise the store hit the STLB
Locked Access (bit 5): The store was part of a locked access if set, otherwise the store was not part of a
locked access.
Reserved
18.9.4.4
A8H
Reserved
Precise Distribution of Instructions Retired (PDIR)
Upon triggering a PEBS assist, there will be a finite delay between the time the counter overflows and when the
microcode starts to carry out its data collection obligations. INST_RETIRED is a very common event that is used to
sample where performance bottleneck happened and to help identify its location in instruction address space. Even
if the delay is constant in core clock space, it invariably manifest as variable “skids” in instruction address space.
This creates a challenge for programmers to profile a workload and pinpoint the location of bottlenecks.
The core PMU in processors based on Intel microarchitecture code name Sandy Bridge include a facility referred to
as precise distribution of Instruction Retired (PDIR).
The PDIR facility mitigates the “skid” problem by providing an early indication of when the INST_RETIRED counter
is about to overflow, allowing the machine to more precisely trap on the instruction that actually caused the
counter overflow thus eliminating skid.
PDIR applies only to the INST_RETIRED.ALL precise event, and must use IA32_PMC1 with PerfEvtSel1 property
configured and bit 1 in the IA32_PEBS_ENABLE set to 1. INST_RETIRED.ALL is a non-architectural performance
event, it is not supported in prior generation microarchitectures. Additionally, on processors with CPUID
DisplayFamily_DisplayModel signatures of 06_2A and 06_2D, the tool that programs PDIR should quiesce the rest
of the programmable counters in the core when PDIR is active.
18.9.5
Off-core Response Performance Monitoring
The core PMU in processors based on Intel microarchitecture code name Sandy Bridge provides off-core response
facility similar to prior generation. Off-core response can be programmed only with a specific pair of event select
and counter MSR, and with specific event codes and predefine mask bit value in a dedicated MSR to specify attributes of the off-core transaction. Two event codes are dedicated for off-core response event programming. Each
event code for off-core response monitoring requires programming an associated configuration MSR,
MSR_OFFCORE_RSP_x. Table 18-35 lists the event code, mask value and additional off-core configuration MSR
that must be programmed to count off-core response events using IA32_PMCx.
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PERFORMANCE MONITORING
Table 18-35. Off-Core Response Event Encoding
Counter
Event code
UMask
Required Off-core Response MSR
PMC0-3
B7H
01H
MSR_OFFCORE_RSP_0 (address 1A6H)
PMC0-3
BBH
01H
MSR_OFFCORE_RSP_1 (address 1A7H)
The layout of MSR_OFFCORE_RSP_0 and MSR_OFFCORE_RSP_1 are shown in Figure 18-36 and Figure 18-37. Bits
15:0 specifies the request type of a transaction request to the uncore. Bits 30:16 specifies supplier information,
bits 37:31 specifies snoop response information.
63
37
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
See Figure 18-30
RESPONSE TYPE — Other (R/W)
RESERVED
REQUEST TYPE — STRM_ST (R/W)
REQUEST TYPE — BUS_LOCKS (R/W)
REQUEST TYPE — PF_LLC_IFETCH (R/W)
REQUEST TYPE — PF_LLC_RFO (R/W)
REQUEST TYPE — PF_LLC_DATA_RD (R/W)
REQUEST TYPE — PF_IFETCH (R/W)
REQUEST TYPE — PF_RFO (R/W)
REQUEST TYPE — PF_DATA_RD (R/W)
REQUEST TYPE — WB (R/W)
REQUEST TYPE — DMND_IFETCH (R/W)
REQUEST TYPE — DMND_RFO (R/W)
REQUEST TYPE — DMND_DATA_RD (R/W)
Reserved
RESET Value — 00000000_00000000H
Figure 18-36. Request_Type Fields for MSR_OFFCORE_RSP_x
Table 18-36. MSR_OFFCORE_RSP_x Request_Type Field Definition
Bit Name
Offset Description
DMND_DATA_RD
0
(R/W). Counts the number of demand data reads of full and partial cachelines as well as demand data
page table entry cacheline reads. Does not count L2 data read prefetches or instruction fetches.
DMND_RFO
1
(R/W). Counts the number of demand and DCU prefetch reads for ownership (RFO) requests generated
by a write to data cacheline. Does not count L2 RFO prefetches.
DMND_IFETCH
2
(R/W). Counts the number of demand and DCU prefetch instruction cacheline reads. Does not count L2
code read prefetches.
WB
3
(R/W). Counts the number of writeback (modified to exclusive) transactions.
PF_DATA_RD
4
(R/W). Counts the number of data cacheline reads generated by L2 prefetchers.
PF_RFO
5
(R/W). Counts the number of RFO requests generated by L2 prefetchers.
PF_IFETCH
6
(R/W). Counts the number of code reads generated by L2 prefetchers.
PF_LLC_DATA_RD
7
(R/W). L2 prefetcher to L3 for loads.
PF_LLC_RFO
8
(R/W). RFO requests generated by L2 prefetcher
PF_LLC_IFETCH
9
(R/W). L2 prefetcher to L3 for instruction fetches.
BUS_LOCKS
10
(R/W). Bus lock and split lock requests
STRM_ST
11
(R/W). Streaming store requests
OTHER
15
(R/W). Any other request that crosses IDI, including I/O.
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PERFORMANCE MONITORING
63
37 36 35 34 33 32 31
22 21 20 19 18 17 16
RESPONSE TYPE — NON_DRAM (R/W)
RSPNS_SNOOP — HITM (R/W)
RSPNS_SNOOP — HIT_FWD
RSPNS_SNOOP — HIT_NO_FWD (R/W)
RSPNS_SNOOP — SNP_MISS (R/W)
RSPNS_SNOOP — SNP_NOT_NEEDED (R/W)
RSPNS_SNOOP — SNPl_NONE (R/W)
RSPNS_SUPPLIER — RESERVED
RSPNS_SUPPLIER — Local
RSPNS_SUPPLIER — LLC_HITF (R/W)
RSPNS_SUPPLIER — LLC_HITS (R/W)
RSPNS_SUPPLIER — LLC_HITE (R/W)
RSPNS_SUPPLIER — LLC_HITM (R/W)
RSPNS_SUPPLIER — No_SUPP (R/W)
RSPNS_SUPPLIER — ANY (R/W)
Reserved
RESET Value — 00000000_00000000H
Figure 18-37. Response_Supplier and Snoop Info Fields for MSR_OFFCORE_RSP_x
To properly program this extra register, software must set at least one request type bit and a valid response type
pattern. Otherwise, the event count reported will be zero. It is permissible and useful to set multiple request and
response type bits in order to obtain various classes of off-core response events. Although MSR_OFFCORE_RSP_x
allow an agent software to program numerous combinations that meet the above guideline, not all combinations
produce meaningful data.
Table 18-37. MSR_OFFCORE_RSP_x Response Supplier Info Field Definition
Subtype
Bit Name
Offset
Description
Common
Any
16
(R/W). Catch all value for any response types.
Supplier
Info
NO_SUPP
17
(R/W). No Supplier Information available
LLC_HITM
18
(R/W). M-state initial lookup stat in L3.
LLC_HITE
19
(R/W). E-state
LLC_HITS
20
(R/W). S-state
LLC_HITF
21
(R/W). F-state
LOCAL
22
(R/W). Local DRAM Controller
Reserved
30:23
Reserved
To specify a complete offcore response filter, software must properly program bits in the request and response type
fields. A valid request type must have at least one bit set in the non-reserved bits of 15:0. A valid response type
must be a non-zero value of the following expression:
ANY | [(‘OR’ of Supplier Info Bits) & (‘OR’ of Snoop Info Bits)]
If “ANY“ bit is set, the supplier and snoop info bits are ignored.
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PERFORMANCE MONITORING
Table 18-38. MSR_OFFCORE_RSP_x Snoop Info Field Definition
Subtype
Bit Name
Offset
Description
Snoop
Info
SNP_NONE
31
(R/W). No details on snoop-related information
SNP_NOT_NEEDED 32
(R/W). No snoop was needed to satisfy the request.
SNP_MISS
(R/W). A snoop was needed and it missed all snooped caches:
33
-For LLC Hit, ReslHitl was returned by all cores
-For LLC Miss, Rspl was returned by all sockets and data was returned from DRAM.
SNP_NO_FWD
34
(R/W). A snoop was needed and it hits in at least one snooped cache. Hit denotes a cacheline was valid before snoop effect. This includes:
-Snoop Hit w/ Invalidation (LLC Hit, RFO)
-Snoop Hit, Left Shared (LLC Hit/Miss, IFetch/Data_RD)
-Snoop Hit w/ Invalidation and No Forward (LLC Miss, RFO Hit S)
In the LLC Miss case, data is returned from DRAM.
SNP_FWD
35
(R/W). A snoop was needed and data was forwarded from a remote socket. This includes:
-Snoop Forward Clean, Left Shared (LLC Hit/Miss, IFetch/Data_RD/RFT).
HITM
36
(R/W). A snoop was needed and it HitM-ed in local or remote cache. HitM denotes a cacheline was in modified state before effect as a results of snoop. This includes:
-Snoop HitM w/ WB (LLC miss, IFetch/Data_RD)
-Snoop Forward Modified w/ Invalidation (LLC Hit/Miss, RFO)
-Snoop MtoS (LLC Hit, IFetch/Data_RD).
NON_DRAM
18.9.6
37
(R/W). Target was non-DRAM system address. This includes MMIO transactions.
Uncore Performance Monitoring Facilities In Intel® Core™ i7-2xxx, Intel® Core™ i52xxx, Intel® Core™ i3-2xxx Processor Series
The uncore sub-system in Intel® Core™ i7-2xxx, Intel® Core™ i5-2xxx, Intel® Core™ i3-2xxx processor series
provides a unified L3 that can support up to four processor cores. The L3 cache consists multiple slices, each slice
interface with a processor via a coherence engine, referred to as a C-Box. Each C-Box provides dedicated facility of
MSRs to select uncore performance monitoring events and each C-Box event select MSR is paired with a counter
register, similar in style as those described in Section 18.8.2.2. The ARB unit in the uncore also provides its local
performance counters and event select MSRs. The layout of the event select MSRs in the C-Boxes and the ARB unit
are shown in Figure 18-38.
63
28
24 23 22 21 20 19 18 17 16 15
Counter Mask
(CMASK)
0
8 7
Unit Mask (UMASK)
Event Select
INV—Invert counter mask
EN—Enable counter
OVF_EN—Overflow forwarding
E—Edge detect
Reserved
RESET Value — 00000000_00000000H
Figure 18-38. Layout of Uncore PERFEVTSEL MSR for a C-Box Unit or the ARB Unit
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PERFORMANCE MONITORING
The bit fields of the uncore event select MSRs for a C-box unit or the ARB unit are summarized below:
•
Event_Select (bits 7:0) and UMASK (bits 15:8): Specifies the microarchitectural condition to count in a local
uncore PMU counter, see Table 19-16.
•
•
E (bit 18): Enables edge detection filtering, if 1.
•
•
•
EN (bit 22): Enables the local counter associated with this event select MSR.
OVF_EN (bit 20): Enables the overflow indicator from the uncore counter forwarded to
MSR_UNC_PERF_GLOBAL_CTRL, if 1.
INV (bit 23): Event count increments with non-negative value if 0, with negated value if 1.
CMASK (bits 28:24): Specifies a positive threshold value to filter raw event count input.
At the uncore domain level, there is a master set of control MSRs that centrally manages all the performance monitoring facility of uncore units. Figure 18-39 shows the layout of the uncore domain global control.
When an uncore counter overflows, a PMI can be routed to a processor core. Bits 3:0 of
MSR_UNC_PERF_GLOBAL_CTRL can be used to select which processor core to handle the uncore PMI. Software
must then write to bit 13 of IA32_DEBUGCTL (at address 1D9H) to enable this capability.
•
PMI_SEL_Core#: Enables the forwarding of an uncore PMI request to a processor core, if 1. If bit 30 (WakePMI)
is ‘1’, a wake request is sent to the respective processor core prior to sending the PMI.
•
EN: Enables the fixed uncore counter, the ARB counters, and the CBO counters in the uncore PMU, if 1. This bit
is cleared if bit 31 (FREEZE) is set and any enabled uncore counters overflow.
•
WakePMI: Controls sending a wake request to any halted processor core before issuing the uncore PMI request.
If a processor core was halted and not sent a wake request, the uncore PMI will not be serviced by the
processor core.
•
FREEZE: Provides the capability to freeze all uncore counters when an overflow condition occurs in a unit
counter. When this bit is set, and a counter overflow occurs, the uncore PMU logic will clear the global enable
bit (bit 29).
63
32 31 30 29 28
4 3 2 1
0
FREEZE—Freeze counters
WakePMI—Wake cores on PMI
EN—Enable all uncore counters
PMI_Sel_Core3 — Uncore PMI to core 3
PMI_Sel_Core2 — Uncore PMI to core 2
PMI_Sel_Core1 — Uncore PMI to core 1
PMI_Sel_Core0 — Uncore PMI to core 0
Reserved
RESET Value — 00000000_00000000H
Figure 18-39. Layout of MSR_UNC_PERF_GLOBAL_CTRL MSR for Uncore
Vol. 3B 18-61
PERFORMANCE MONITORING
Additionally, there is also a fixed counter, counting uncore clockticks, for the uncore domain. Table 18-39 summarizes the number MSRs for uncore PMU for each box.
Table 18-39. Uncore PMU MSR Summary
Box
# of Boxes
Counters per
Box
Counter
Width
General
Purpose
Global
Enable
C-Box
SKU specific
2
44
Yes
Per-box
ARB
1
2
44
Yes
Uncore
Fixed
Counter
N.A.
N.A.
48
No
Uncore
18.9.6.1
Comment
Up to 4, seeTable 35-19
MSR_UNC_CBO_CONFIG
Uncore Performance Monitoring Events
There are certain restrictions on the uncore performance counters in each C-Box. Specifically,
•
Occupancy events are supported only with counter 0 but not counter 1.
Other uncore C-Box events can be programmed with either counter 0 or 1.
The C-Box uncore performance events described in Table 19-16 can collect performance characteristics of transactions initiated by processor core. In that respect, they are similar to various sub-events in the
OFFCORE_RESPONSE family of performance events in the core PMU. Information such as data supplier locality
(LLC HIT/MISS) and snoop responses can be collected via OFFCORE_RESPONSE and qualified on a per-thread
basis.
On the other hand, uncore performance event logic can not associate its counts with the same level of per-thread
qualification attributes as the core PMU events can. Therefore, whenever similar event programming capabilities
are available from both core PMU and uncore PMU, the recommendation is that utilizing the core PMU events may
be less affected by artifacts, complex interactions and other factors.
18.9.7
Intel® Xeon® Processor E5 Family Performance Monitoring Facility
The Intel® Xeon® Processor E5 Family (and Intel® Core™ i7-3930K Processor) are based on Intel microarchitecture code name Sandy Bridge-E. While the processor cores share the same microarchitecture as those of the Intel®
Xeon® Processor E3 Family and 2nd generation Intel Core i7-2xxx, Intel Core i5-2xxx, Intel Core i3-2xxx processor
series, the uncore subsystems are different. An overview of the uncore performance monitoring facilities of the
Intel Xeon processor E5 family (and Intel Core i7-3930K processor) is described in Section 18.9.8.
Thus, the performance monitoring facilities in the processor core generally are the same as those described in
Section 18.9 through Section 18.9.5. However, the MSR_OFFCORE_RSP_0/MSR_OFFCORE_RSP_1 Response
Supplier Info field shown in Table 18-37 applies to Intel Core Processors with CPUID signature of
DisplayFamily_DisplayModel encoding of 06_2AH; Intel Xeon processor with CPUID signature of
DisplayFamily_DisplayModel encoding of 06_2DH supports an additional field for remote DRAM controller shown in
Table 18-40. Additionally, the are some small differences in the non-architectural performance monitoring events
(see Table 19-14).
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Table 18-40. MSR_OFFCORE_RSP_x Supplier Info Field Definitions
Subtype
Bit Name
Offset
Description
Common
Any
16
(R/W). Catch all value for any response types.
Supplier Info
NO_SUPP
17
(R/W). No Supplier Information available
LLC_HITM
18
(R/W). M-state initial lookup stat in L3.
LLC_HITE
19
(R/W). E-state
18.9.8
LLC_HITS
20
(R/W). S-state
LLC_HITF
21
(R/W). F-state
LOCAL
22
(R/W). Local DRAM Controller
Remote
30:23
(R/W): Remote DRAM Controller (either all 0s or all 1s)
Intel® Xeon® Processor E5 Family Uncore Performance Monitoring Facility
The uncore subsystem in the Intel Xeon processor E5-2600 product family has some similarities with those of the
Intel Xeon processor E7 family. Within the uncore subsystem, localized performance counter sets are provided at
logic control unit scope. For example, each Cbox caching agent has a set of local performance counters, and the
power controller unit (PCU) has its own local performance counters. Up to 8 C-Box units are supported in the
uncore sub-system.
Table 18-41 summarizes the uncore PMU facilities providing MSR interfaces.
Table 18-41. Uncore PMU MSR Summary for Intel® Xeon® Processor E5 Family
Box
# of Boxes
Counters per Box
Counter
Width
General
Purpose
Global
Enable
Sub-control MSRs
C-Box
8
4
44
Yes
per-box
None
PCU
1
4
48
Yes
per-box
Match/Mask
U-Box
1
2
44
Yes
uncore
None
Details of the uncore performance monitoring facility of Intel Xeon Processor E5 family is available in “Intel®
Xeon® Processor E5 Uncore Performance Monitoring Programming Reference Manual”. The MSR-based uncore
PMU interfaces are listed in Table 35-22.
18.10
3RD GENERATION INTEL® CORE™ PROCESSOR PERFORMANCE
MONITORING FACILITY
The 3rd generation Intel® Core™ processor family and Intel® Xeon® processor E3-1200v2 product family are
based on the Ivy Bridge microarchitecture. The performance monitoring facilities in the processor core generally
are the same as those described in Section 18.9 through Section 18.9.5. The non-architectural performance monitoring events supported by the processor core are listed in Table 19-14.
18.10.1 Intel® Xeon® Processor E5 v2 and E7 v2 Family Uncore Performance Monitoring
Facility
The uncore subsystem in the Intel Xeon processor E5 v2 and Intel Xeon Processor E7 v2 product families are based
on the Ivy Bridge-E microarchitecture. There are some similarities with those of the Intel Xeon processor E5 family
based on the Sandy Bridge microarchitecture. Within the uncore subsystem, localized performance counter sets
are provided at logic control unit scope.
Vol. 3B 18-63
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Details of the uncore performance monitoring facility of Intel Xeon Processor E5 v2 and Intel Xeon Processor E7 v2
families are available in “Intel® Xeon® Processor E5 v2 and E7 v2 Uncore Performance Monitoring Programming
Reference Manual”. The MSR-based uncore PMU interfaces are listed in Table 35-26.
18.11
4TH GENERATION INTEL® CORE™ PROCESSOR PERFORMANCE
MONITORING FACILITY
The 4th generation Intel® Core™ processor and Intel® Xeon® processor E3-1200 v3 product family are based on
the Haswell microarchitecture. The core PMU supports architectural performance monitoring capability with version
ID 3 (see Section 18.2.3) and a host of non-architectural monitoring capabilities.
Architectural performance monitoring version 3 capabilities are described in Section 18.2.3.
The core PMU’s capability is similar to those described in Section 18.9 through Section 18.9.5, with some differences and enhancements summarized in Table 18-42. Additionally, the core PMU provides some enhancement to
support performance monitoring when the target workload contains instruction streams using Intel® Transactional
Synchronization Extensions (TSX), see Section 18.11.5. For details of Intel TSX, see Chapter 15, “Programming with
Intel® Transactional Synchronization Extensions” of Intel® 64 and IA-32 Architectures Software Developer’s
Manual, Volume 1.
Table 18-42. Core PMU Comparison
Box
Intel® microarchitecture code
name Haswell
Intel® microarchitecture code
name Sandy Bridge
Comment
# of Fixed counters per thread
3
3
# of general-purpose counters
per core
8
8
Counter width (R,W)
R:48, W: 32/48
R:48, W: 32/48
See Section 18.2.2.
# of programmable counters per
thread
4 or (8 if a core not shared by two
threads)
4 or (8 if a core not shared by
two threads)
Use CPUID to enumerate
# of counters.
PMI Overhead Mitigation
• Freeze_Perfmon_on_PMI with
legacy semantics.
• Freeze_on_LBR with legacy
semantics for branch profiling.
• Freeze_while_SMM.
• Freeze_Perfmon_on_PMI
with legacy semantics.
• Freeze_on_LBR with legacy
semantics for branch
profiling.
• Freeze_while_SMM.
See Section 17.4.7.
Processor Event Based Sampling
(PEBS) Events
See Table 18-32 and Section
18.11.5.1.
See Table 18-32.
IA32_PMC4-IA32_PMC7
do not support PEBS.
PEBS-Load Latency
See Section 18.9.4.2.
See Section 18.9.4.2.
PEBS-Precise Store
No, replaced by Data Address
profiling.
Section 18.9.4.3
PEBS-PDIR
Yes (using precise
INST_RETIRED.ALL)
Yes (using precise
INST_RETIRED.ALL)
PEBS-EventingIP
Yes
No
Data Address Profiling
Yes
No
LBR Profiling
Yes
Yes
Call Stack Profiling
Yes, see Section 17.9.
No
Off-core Response Event
MSR 1A6H and 1A7H; extended
request and response types.
MSR 1A6H and 1A7H; extended
request and response types.
Intel TSX support for Perfmon
See Section 18.11.5.
No
18-64 Vol. 3B
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PERFORMANCE MONITORING
18.11.1 Processor Event Based Sampling (PEBS) Facility
The PEBS facility in the 4th Generation Intel Core processor is similar to those in processors based on Intel microarchitecture code name Sandy Bridge, with several enhanced features. The key components and differences of
PEBS facility relative to Intel microarchitecture code name Sandy Bridge is summarized in Table 18-43.
Table 18-43. PEBS Facility Comparison
Box
Intel® microarchitecture code
name Haswell
Intel® microarchitecture code
name Sandy Bridge
Comment
Valid IA32_PMCx
PMC0-PMC3
PMC0-PMC3
No PEBS on PMC4-PMC7
PEBS Buffer Programming
Section 18.8.1.1
Section 18.8.1.1
Unchanged
IA32_PEBS_ENABLE Layout
Figure 18-21
Figure 18-35
PEBS record layout
Table 18-44; enhanced fields at
offsets 98H, A0H, A8H, B0H.
Table 18-23; enhanced fields
at offsets 98H, A0H, A8H.
Precise Events
See Table 18-32.
See Table 18-32.
PEBS-Load Latency
See Table 18-33.
Table 18-33
PEBS-Precise Store
No, replaced by data address
profiling.
Yes; see Section 18.9.4.3.
PEBS-PDIR
Yes
Yes
PEBS skid from EventingIP
1 (or 2 if micro+macro fusion)
1
SAMPLING Restriction
Small SAV(CountDown) value incur higher overhead than prior
generation.
IA32_PMC4-IA32_PMC7 do not
support PEBS.
IA32_PMC1 only.
Only IA32_PMC0 through IA32_PMC3 support PEBS.
NOTE
PEBS events are only valid when the following fields of IA32_PERFEVTSELx are all zero: AnyThread,
Edge, Invert, CMask.
In a PMU with PDIR capability, PEBS behavior is unpredictable if IA32_PERFEVTSELx or IA32_PMCx
is changed for a PEBS-enabled counter while an event is being counted. To avoid this, changes to
the programming or value of a PEBS-enabled counter should be performed when the counter is
disabled.
18.11.2 PEBS Data Format
The PEBS record format for the 4th Generation Intel Core processor is shown in Table 18-44. The PEBS record
format, along with debug/store area storage format, does not change regardless of whether IA-32e mode is active
or not. CPUID.01H:ECX.DTES64[bit 2] reports whether the processor's DS storage format support is mode-independent. When set, it uses 64-bit DS storage format.
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PERFORMANCE MONITORING
Table 18-44. PEBS Record Format for 4th Generation Intel Core Processor Family
Byte Offset
Field
Byte Offset
Field
00H
R/EFLAGS
60H
R10
08H
R/EIP
68H
R11
10H
R/EAX
70H
R12
18H
R/EBX
78H
R13
20H
R/ECX
80H
R14
28H
R/EDX
88H
R15
30H
R/ESI
90H
IA32_PERF_GLOBAL_STATUS
38H
R/EDI
98H
Data Linear Address
40H
R/EBP
A0H
Data Source Encoding
48H
R/ESP
A8H
Latency value (core cycles)
50H
R8
B0H
EventingIP
58H
R9
B8H
TX Abort Information (Section 18.11.5.1)
The layout of PEBS records are almost identical to those shown in Table 18-23. Offset B0H is a new field that
records the eventing IP address of the retired instruction that triggered the PEBS assist.
The PEBS records at offsets 98H, A0H, and ABH record data gathered from three of the PEBS capabilities in prior
processor generations: load latency facility (Section 18.9.4.2), PDIR (Section 18.9.4.4), and the equivalent capability of precise store in prior generation (see Section 18.11.3).
In the core PMU of the 4th generation Intel Core processor, load latency facility and PDIR capabilities are
unchanged. However, precise store is replaced by an enhanced capability, data address profiling, that is not
restricted to store address. Data address profiling also records information in PEBS records at offsets 98H, A0H,
and ABH.
18.11.3 PEBS Data Address Profiling
The Data Linear Address facility is also abbreviated as DataLA. The facility is a replacement or extension of the
precise store facility in previous processor generations. The DataLA facility complements the load latency facility by
providing a means to profile load and store memory references in the system, leverages the PEBS facility, and
provides additional information about sampled loads and stores. Having precise memory reference events with
linear address information for both loads and stores provides information to improve data structure layout, eliminate remote node references, and identify cache-line conflicts in NUMA systems.
The DataLA facility in the 4th generation processor supports the following events configured to use PEBS:
Table 18-45. Precise Events That Supports Data Linear Address Profiling
Event Name
Event Name
MEM_UOPS_RETIRED.STLB_MISS_LOADS
MEM_UOPS_RETIRED.STLB_MISS_STORES
MEM_UOPS_RETIRED.LOCK_LOADS
MEM_UOPS_RETIRED.SPLIT_STORES
MEM_UOPS_RETIRED.SPLIT_LOADS
MEM_UOPS_RETIRED.ALL_STORES
MEM_UOPS_RETIRED.ALL_LOADS
MEM_LOAD_UOPS_LLC_MISS_RETIRED.LOCAL_DRAM
MEM_LOAD_UOPS_RETIRED.L1_HIT
MEM_LOAD_UOPS_RETIRED.L2_HIT
MEM_LOAD_UOPS_RETIRED.L3_HIT
MEM_LOAD_UOPS_RETIRED.L1_MISS
MEM_LOAD_UOPS_RETIRED.L2_MISS
MEM_LOAD_UOPS_RETIRED.L3_MISS
MEM_LOAD_UOPS_RETIRED.HIT_LFB
MEM_LOAD_UOPS_L3_HIT_RETIRED.XSNP_MISS
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PERFORMANCE MONITORING
Table 18-45. Precise Events That Supports Data Linear Address Profiling (Contd.)
Event Name
Event Name
MEM_LOAD_UOPS_L3_HIT_RETIRED.XSNP_HIT
MEM_LOAD_UOPS_L3_HIT_RETIRED.XSNP_HITM
UOPS_RETIRED.ALL (if load or store is tagged)
MEM_LOAD_UOPS_LLC_HIT_RETIRED.XSNP_NONE
DataLA can use any one of the IA32_PMC0-IA32_PMC3 counters. Counter overflows will initiate the generation of
PEBS records. Upon counter overflow, hardware captures the linear address and possible other status information
of the retiring memory uop. This information is then written to the PEBS record that is subsequently generated.
To enable the DataLA facility, software must complete the following steps. Please note that the DataLA facility relies
on the PEBS facility, so the PEBS configuration requirements must be completed before attempting to capture
DataLA information.
•
•
•
Complete the PEBS configuration steps.
Program the an event listed in Table 18-45 using any one of IA32_PERFEVTSEL0-IA32_PERFEVTSEL3.
Set the corresponding IA32_PEBS_ENABLE.PEBS_EN_CTRx bit. This enables the corresponding IA32_PMCx as
a PEBS counter and enables the DataLA facility.
When the DataLA facility is enabled, the relevant information written into a PEBS record affects entries at offsets
98H, A0H and A8H, as shown in Table 18-46.
Table 18-46. Layout of Data Linear Address Information In PEBS Record
Field
Offset
Description
Data Linear
Address
98H
The linear address of the load or the destination of the store.
Store Status
A0H
• DCU Hit (Bit 0): The store hit the data cache closest to the core (L1 cache) if this bit is set, otherwise
the store missed the data cache. This information is valid only for the following store events:
UOPS_RETIRED.ALL (if store is tagged),
MEM_UOPS_RETIRED.STLB_MISS_STORES,
MEM_UOPS_RETIRED.SPLIT_STORES, MEM_UOPS_RETIRED.ALL_STORES
• Other bits are zero, The STLB_MISS, LOCK bit information can be obtained by programming the
corresponding store event in Table 18-45.
Reserved
A8H
Always zero.
18.11.3.1 EventingIP Record
The PEBS record layout for processors based on Intel microarchitecture code name Haswell adds a new field at
offset 0B0H. This is the eventingIP field that records the IP address of the retired instruction that triggered the
PEBS assist. The EIP/RIP field at offset 08H records the IP address of the next instruction to be executed following
the PEBS assist.
18.11.4 Off-core Response Performance Monitoring
The core PMU facility to collect off-core response events are similar to those described in Section 18.9.5. The event
codes are listed in Table 18-35. Each event code for off-core response monitoring requires programming an associated configuration MSR, MSR_OFFCORE_RSP_x. Software must program MSR_OFFCORE_RSP_x according to:
•
•
•
Transaction request type encoding (bits 15:0): see Table 18-47.
Supplier information (bits 30:16): see Table 18-48 and Table 18-48.
Snoop response information (bits 37:31): see Table 18-38.
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PERFORMANCE MONITORING
Table 18-47. MSR_OFFCORE_RSP_x Request_Type Definition (Haswell microarchitecture)
Bit Name
Offset Description
DMND_DATA_RD
0
(R/W). Counts the number of demand data reads of full and partial cachelines as well as demand data
page table entry cacheline reads. Does not count L2 data read prefetches or instruction fetches.
DMND_RFO
1
(R/W). Counts the number of demand and DCU prefetch reads for ownership (RFO) requests generated
by a write to data cacheline. Does not count L2 RFO prefetches.
DMND_IFETCH
2
(R/W). Counts the number of demand and DCU prefetch instruction cacheline reads. Does not count L2
code read prefetches.
Reserved
3
Reserved
PF_DATA_RD
4
(R/W). Counts the number of data cacheline reads generated by L2 prefetchers.
PF_RFO
5
(R/W). Counts the number of RFO requests generated by L2 prefetchers.
PF_IFETCH
6
(R/W). Counts the number of code reads generated by L2 prefetchers.
Reserved
7-14
Reserved
OTHER
15
(R/W). Any other request that crosses IDI, including I/O.
The supplier information field listed in Table 18-48 and Table 18-48. The fields vary across products (according to
CPUID signatures) and is noted in the description.
Table 18-48. MSR_OFFCORE_RSP_x Supplier Info Field Definition (CPUID Signature 06_3CH, 06_46H)
Subtype
Bit Name
Offset
Description
Common
Any
16
(R/W). Catch all value for any response types.
Supplier
Info
NO_SUPP
17
(R/W). No Supplier Information available
L3_HITM
18
(R/W). M-state initial lookup stat in L3.
L3_HITE
19
(R/W). E-state
L3_HITS
20
(R/W). S-state
Reserved
21
Reserved
LOCAL
22
(R/W). Local DRAM Controller
Reserved
30:23
Reserved
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PERFORMANCE MONITORING
Table 18-49. MSR_OFFCORE_RSP_x Supplier Info Field Definition (CPUID Signature 06_45H)
Subtype
Bit Name
Offset
Description
Common
Any
16
(R/W). Catch all value for any response types.
Supplier
Info
NO_SUPP
17
(R/W). No Supplier Information available
L3_HITM
18
(R/W). M-state initial lookup stat in L3.
L3_HITE
19
(R/W). E-state
L3_HITS
20
(R/W). S-state
Reserved
21
Reserved
L4_HIT_LOCAL_L4
22
(R/W). L4 Cache
L4_HIT_REMOTE_HOP0_L4
23
(R/W). L4 Cache
L4_HIT_REMOTE_HOP1_L4
24
(R/W). L4 Cache
L4_HIT_REMOTE_HOP2P_L4
25
(R/W). L4 Cache
Reserved
30:26
Reserved
18.11.4.1 Off-core Response Performance Monitoring in Intel Xeon Processors E5 v3 Series
Table 18-48 lists the supplier information field that apply to Intel Xeon processor E5 v3 series (CPUID signature
06_3FH).
Table 18-50. MSR_OFFCORE_RSP_x Supplier Info Field Definition
Subtype
Bit Name
Offset
Description
Common
Any
16
(R/W). Catch all value for any response types.
Supplier
Info
NO_SUPP
17
(R/W). No Supplier Information available
L3_HITM
18
(R/W). M-state initial lookup stat in L3.
L3_HITE
19
(R/W). E-state
L3_HITS
20
(R/W). S-state
L3_HITF
21
(R/W). F-state
LOCAL
22
(R/W). Local DRAM Controller
Reserved
26:23
Reserved
L3_MISS_REMOTE_HOP0
27
(R/W). Hop 0 Remote supplier
L3_MISS_REMOTE_HOP1
28
(R/W). Hop 1 Remote supplier
L3_MISS_REMOTE_HOP2P
29
(R/W). Hop 2 or more Remote supplier
Reserved
30
Reserved
18.11.5 Performance Monitoring and Intel® TSX
Chapter 15 of Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 1 describes the details of
Intel® Transactional Synchronization Extensions (Intel TSX). This section describes performance monitoring
support for Intel TSX.
If a processor supports Intel TSX, the core PMU enhances it’s IA32_PERFEVTSELx MSR with two additional bit fields
for event filtering. Support for Intel TSX is indicated by either (a) CPUID.(EAX=7, ECX=0):RTM[bit 11]=1, or (b) if
CPUID.07H.EBX.HLE [bit 4] = 1. The TSX-enhanced layout of IA32_PERFEVTSELx is shown in Figure 18-40. The
two additional bit fields are:
Vol. 3B 18-69
PERFORMANCE MONITORING
•
IN_TX (bit 32): When set, the counter will only include counts that occurred inside a transactional region,
regardless of whether that region was aborted or committed. This bit may only be set if the processor supports
HLE or RTM.
•
IN_TXCP (bit 33): When set, the counter will not include counts that occurred inside of an aborted transactional region. This bit may only be set if the processor supports HLE or RTM. This bit may only be set for
IA32_PERFEVTSEL2.
When the IA32_PERFEVTSELx MSR is programmed with both IN_TX=0 and IN_TXCP=0 on a processor that
supports Intel TSX, the result in a counter may include detectable conditions associated with a transaction code
region for its aborted execution (if any) and completed execution.
In the initial implementation, software may need to take pre-caution when using the IN_TXCP bit. see Table 35-27.
63
34
Reserved
31
24 23 22 21 20 19 18 17 16 15
8 7
A I
U
Counter Mask I E N
N
N P E O S Unit Mask (UMASK)
(CMASK)
S R
V N Y T C
0
Event Select
USR—User Mode
OS—Operating system mode
E—Edge detect
PC—Pin control
INT—APIC interrupt enable
ANY—Any Thread
EN—Enable counters
INV—Invert counter mask
IN_TX—In Trans. Rgn
IN_TXCP—In Tx exclude abort (PERFEVTSEL2 Only)
Figure 18-40. Layout of IA32_PERFEVTSELx MSRs Supporting Intel TSX
A common usage of setting IN_TXCP=1 is to capture the number of events that were discarded due to a transactional abort. With IA32_PMC2 configured to count in such a manner, then when a transactional region aborts, the
value for that counter is restored to the value it had prior to the aborted transactional region. As a result, any
updates performed to the counter during the aborted transactional region are discarded.
On the other hand, setting IN_TX=1 can be used to drill down on the performance characteristics of transactional
code regions. When a PMCx is configured with the corresponding IA32_PERFEVTSELx.IN_TX=1, only eventing
conditions that occur inside transactional code regions are propagated to the event logic and reflected in the
counter result. Eventing conditions specified by IA32_PERFEVTSELx but occurring outside a transactional region
are discarded. The following example illustrates using three counters to drill down cycles spent inside and outside
of transactional regions:
•
Program IA32_PERFEVTSEL2 to count Unhalted_Core_Cycles with (IN_TXCP=1, IN_TX=0), such that
IA32_PMC2 will count cycles spent due to aborted TSX transactions;
•
Program IA32_PERFEVTSEL0 to count Unhalted_Core_Cycles with (IN_TXCP=0, IN_TX=1), such that
IA32_PMC0 will count cycles spent by the transactional code regions;
•
Program IA32_PERFEVTSEL1 to count Unhalted_Core_Cycles with (IN_TXCP=0, IN_TX=0), such that
IA32_PMC1 will count total cycles spent by the non-transactional code and transactional code regions.
Additionally, a number of performance events are solely focused on characterizing the execution of Intel TSX transactional code, they are listed in Table 19-8.
18.11.5.1 Intel TSX and PEBS Support
If a PEBS event would have occurred inside a transactional region, then the transactional region first aborts, and
then the PEBS event is processed.
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PERFORMANCE MONITORING
Two of the TSX performance monitoring events in Table 19-8 also support using PEBS facility to capture additional
information. They are:
•
•
HLE_RETIRED.ABORT ED (encoding C8H mask 04H),
RTM_RETIRED.ABORTED (encoding C9H mask 04H).
A transactional abort (HLE_RETIRED.ABORTED,RTM_RETIRED.ABORTED) can also be programmed to cause PEBS
events. In this scenario, a PEBS event is processed following the abort.
Pending a PEBS record inside of a transactional region will cause a transactional abort. If a PEBS record was pended
at the time of the abort or on an overflow of the TSX PEBS events listed above, only the following PEBS entries will
be valid (enumerated by PEBS entry offset B8H bits[33:32] to indicate an HLE abort or an RTM abort):
•
•
Offset B0H: EventingIP,
Offset B8H: TX Abort Information
These fields are set for all PEBS events.
•
Offset 08H (RIP/EIP) corresponds to the instruction following the outermost XACQUIRE in HLE or the first
instruction of the fallback handler of the outermost XBEGIN instruction in RTM. This is useful to identify the
aborted transactional region.
In the case of HLE, an aborted transaction will restart execution deterministically at the start of the HLE region. In
the case of RTM, an aborted transaction will transfer execution to the RTM fallback handler.
The layout of the TX Abort Information field is given in Table 18-51.
Table 18-51. TX Abort Information Field Definition
Bit Name
Offset
Description
Cycles_Last_TX
31:0
The number of cycles in the last TSX region, regardless of whether that region had aborted or
committed.
HLE_Abort
32
If set, the abort information corresponds to an aborted HLE execution
RTM_Abort
33
If set, the abort information corresponds to an aborted RTM execution
Instruction_Abort
34
If set, the abort was associated with the instruction corresponding to the eventing IP (offset
0B0H) within the transactional region.
Non_Instruction_Abort
35
If set, the instruction corresponding to the eventing IP may not necessarily be related to the
transactional abort.
Retry
36
If set, retrying the transactional execution may have succeeded.
Data_Conflict
37
If set, another logical processor conflicted with a memory address that was part of the
transactional region that aborted.
Capacity Writes
38
If set, the transactional region aborted due to exceeding resources for transactional writes.
Capacity Reads
39
If set, the transactional region aborted due to exceeding resources for transactional reads.
Reserved
63:40
Reserved
18.11.6 Uncore Performance Monitoring Facilities in the 4th Generation Intel® Core™
Processors
The uncore sub-system in the 4th Generation Intel® Core™ processors provides its own performance monitoring
facility. The uncore PMU facility provides dedicated MSRs to select uncore performance monitoring events in a
similar manner as those described in Section 18.9.6.
The ARB unit and each C-Box provide local pairs of event select MSR and counter register. The layout of the event
select MSRs in the C-Boxes are identical as shown in Figure 18-38.
At the uncore domain level, there is a master set of control MSRs that centrally manages all the performance monitoring facility of uncore units. Figure 18-39 shows the layout of the uncore domain global control.
Vol. 3B 18-71
PERFORMANCE MONITORING
Additionally, there is also a fixed counter, counting uncore clockticks, for the uncore domain. Table 18-39 summarizes the number MSRs for uncore PMU for each box.
Table 18-52. Uncore PMU MSR Summary
Box
# of Boxes
Counters per
Box
Counter
Width
General
Purpose
Global
Enable
C-Box
SKU specific
2
44
Yes
Per-box
ARB
1
2
44
Yes
Uncore
Fixed Counter
N.A.
N.A.
48
No
Uncore
Comment
Up to 4, seeTable 35-19
MSR_UNC_CBO_CONFIG
The uncore performance events for the C-Box and ARB units are listed in Table 19-9.
18.11.7 Intel® Xeon® Processor E5 v3 Family Uncore Performance Monitoring Facility
Details of the uncore performance monitoring facility of Intel Xeon Processor E5 v3 families are available in “Intel®
Xeon® Processor E5 v3 Uncore Performance Monitoring Programming Reference Manual”. The MSR-based uncore
PMU interfaces are listed in Table 35-31.
18.12
INTEL® CORE™ M PROCESSOR PERFORMANCE MONITORING FACILITY
The Intel® Core™ M processor and the 5th Generation Intel Core processor families are based on the Broadwell
microarchitecture. The core PMU supports architectural performance monitoring capability with version ID 3 (see
Section 18.2.3) and a host of non-architectural monitoring capabilities.
Architectural performance monitoring version 3 capabilities are described in Section 18.2.3.
The core PMU has the same capability as those described in Section 18.11. IA32_PERF_GLOBAL_STATUS provide a
bit indicator (bit 55) for PMI handler to distinguish PMI due to output buffer overflow condition due to accumulating
packet data from Intel Processor Trace.
63 62 61
55
35 34 33 32 31
8 7 6 5 4 3 2 1 0
CondChgd
Ovf_Buffer
Ovf_UncorePMU
Trace_ToPA_PMI
FIXED_CTR2 Overflow (RO)
FIXED_CTR1 Overflow (RO)
FIXED_CTR0 Overflow (RO)
PMC7_OVF (RO, If PMC7 present)
PMC6_OVF (RO, If PMC6 present)
PMC5_OVF (RO, If PMC5 present)
PMC4_OVF (RO, If PMC4 present)
PMC3_OVF (RO)
PMC2_OVF (RO)
PMC1_OVF (RO)
PMC0_OVF (RO)
Reserved
Valid if CPUID.0AH:EAX[15:8] = 8; else reserved
Figure 18-41. IA32_PERF_GLOBAL_STATUS MSR in Broadwell Microarchitecture
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PERFORMANCE MONITORING
Details of Intel Processor Trace is described in Chapter 36, “Intel® Processor Trace”.
IA32_PERF_GLOBAL_OVF_CTRL MSR provide a corresponding reset control bit.
63 62 61
55
35 34 33 32 31
8 7 6 5 4 3
2 1 0
ClrCondChgd
ClrOvfDSBuffer
ClrOvfUncore
ClrTraceToPA_PMI
FIXED_CTR2 ClrOverflow
FIXED_CTR1 ClrOverflow
FIXED_CTR0 ClrOverflow
PMC7_ClrOvf (if PMC7 present)
PMC6_ClrOvf (if PMC6 present)
PMC5_ClrOvf (if PMC5 present)
PMC4_ClrOvf (if PMC4 present)
PMC3_ClrOvf
PMC2_ClrOvf
PMC1_ClrOvf
PMC0_ClrOvf
Reserved
Valid if CPUID.0AH:EAX[15:8] = 8; else reserved
Figure 18-42. IA32_PERF_GLOBAL_OVF_CTRL MSR in Broadwell microarchitecture
The specifics of non-architectural performance events are listed in Chapter 19, “Performance Monitoring Events”.
18.13
6TH GENERATION INTEL® CORE™ PROCESSOR PERFORMANCE
MONITORING FACILITY
The 6th generation Intel® Core™ processor is based on the Skylake microarchitecture. The core PMU supports
architectural performance monitoring capability with version ID 4 (see Section 18.2.4) and a host of non-architectural monitoring capabilities.
Architectural performance monitoring version 4 capabilities are described in Section 18.2.4.
The core PMU’s capability is similar to those described in Section 18.9 through Section 18.9.5, with some differences and enhancements summarized in Table 18-42. Additionally, the core PMU provides some enhancement to
support performance monitoring when the target workload contains instruction streams using Intel® Transactional
Synchronization Extensions (TSX), see Section 18.11.5. For details of Intel TSX, see Chapter 15, “Programming with
Intel® Transactional Synchronization Extensions” of Intel® 64 and IA-32 Architectures Software Developer’s
Manual, Volume 1.
Performance monitoring result may be affected by side-band activity on processors that support Intel SGX, details
are described in Chapter 43, “Enclave Code Debug and Profiling”.
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PERFORMANCE MONITORING
Table 18-53. Core PMU Comparison
Box
Intel® microarchitecture code name
Skylake
Intel® microarchitecture code
name Haswell and Broadwell
# of Fixed counters per thread
3
3
# of general-purpose counters
per core
8
8
Counter width (R,W)
R:48, W: 32/48
R:48, W: 32/48
See Section 18.2.2.
# of programmable counters
per thread
4 or (8 if a core not shared by two
threads)
4 or (8 if a core not shared by two
threads)
CPUID enumerates
# of counters.
Architectural Perfmon version
4
3
See Section 18.2.4
PMI Overhead Mitigation
• Freeze_Perfmon_on_PMI with
streamlined semantics.
• Freeze_on_LBR with streamlined
semantics.
• Freeze_while_SMM.
• Freeze_Perfmon_on_PMI with
legacy semantics.
• Freeze_on_LBR with legacy
semantics for branch profiling.
• Freeze_while_SMM.
See Section 17.4.7.
Comment
Legacy semantics
not supported with
version 4 or higher.
Counter and Buffer Overflow
Status Management
• Query via
• Query via
IA32_PERF_GLOBAL_STATUS
IA32_PERF_GLOBAL_STATUS
• Reset via
• Reset via
IA32_PERF_GLOBAL_OVF_CTRL
IA32_PERF_GLOBAL_STATUS_RESET
• Set via
IA32_PERF_GLOBAL_STATUS_SET
See Section 18.2.4.
IA32_PERF_GLOBAL_STATUS
Indicators of
Overflow/Overhead/Interferen
ce
•
•
•
•
• Individual counter overflow
• PEBS buffer overflow
• ToPA buffer overflow (applicable
to Broadwell microarchitecture)
See Section 18.2.4.
Enable control in
IA32_PERF_GLOBAL_STATUS
• CTR_Frz,
• LBR_Frz
NA
See Section
18.2.4.1.
Perfmon Counter In-Use
Indicator
Query IA32_PERF_GLOBAL_INUSE
NA
See Section
18.2.4.3.
Precise Events
See Table 18-56.
See Table 18-32.
IA32_PMC4-PMC7
do not support
PEBS.
PEBS for front end events
See Section 18.13.1.4;
No
LBR Record Format Encoding
000101b
000100b
LBR Size
32 entries
16 entries
LBR Entry
From_IP/To_IP/LBR_Info triplet
From_IP/To_IP pair
Section 17.10
LBR Timing
Yes
No
Section 17.10.1
Call Stack Profiling
Yes, see Section 17.9
Yes, see Section 17.9
Use LBR facility
Off-core Response Event
MSR 1A6H and 1A7H; Extended request
and response types.
MSR 1A6H and 1A7H; Extended
request and response types.
Intel TSX support for Perfmon
See Section 18.11.5;
See Section 18.11.5;
Individual counter overflow
PEBS buffer overflow
ToPA buffer overflow
CTR_Frz, LBR_Frz, ASCI
Section 17.4.8.1
18.13.1 Processor Event Based Sampling (PEBS) Facility
The PEBS facility in the 6th Generation Intel Core processor provides a number enhancement relative to PEBS in
processors based on Haswell/Broadwell microarchitectures. The key components and differences of PEBS facility
relative to Haswell/Broadwell microarchitecture is summarized in Table 18-54.
18-74 Vol. 3B
PERFORMANCE MONITORING
Table 18-54. PEBS Facility Comparison
Box
Intel® microarchitecture code
name Skylake
Intel® microarchitecture code
name Haswell and Broadwell
Comment
Valid IA32_PMCx
PMC0-PMC3
PMC0-PMC3
No PEBS on PMC4-PMC7.
PEBS Buffer Programming
Section 18.8.1.1
Section 18.8.1.1
Unchanged
IA32_PEBS_ENABLE Layout
Figure 18-21
Figure 18-21
PEBS-EventingIP
Yes
Yes
PEBS record format encoding 0011b
0010b
PEBS record layout
Table 18-55; enhanced fields
at offsets 98H- B8H; and TSC
record field at C0H.
Table 18-44; enhanced fields at
offsets 98H, A0H, A8H, B0H.
Multi-counter PEBS
resolution
PEBS record 90H resolves the
eventing counter overflow.
PEBS record 90H reflects
IA32_PERF_GLOBAL_STATUS.
Precise Events
See Table 18-56.
See Table 18-32.
IA32_PMC4-IA32_PMC7 do not
support PEBS.
PEBS-PDIR
Yes
Yes
IA32_PMC1 only.
PEBS-Load Latency
See Section 18.9.4.2.
See Section 18.9.4.2.
Data Address Profiling
Yes
Yes
FrontEnd event support
FrontEnd_Retried event and
MSR_PEBS_FRONTEND.
No
IA32_PMC0-PMC3 only.
Only IA32_PMC0 through IA32_PMC3 support PEBS.
NOTES
Precise events are only valid when the following fields of IA32_PERFEVTSELx are all zero:
AnyThread, Edge, Invert, CMask.
In a PMU with PDIR capability, PEBS behavior is unpredictable if IA32_PERFEVTSELx or IA32_PMCx
is changed for a PEBS-enabled counter while an event is being counted. To avoid this, changes to
the programming or value of a PEBS-enabled counter should be performed when the counter is
disabled.
18.13.1.1 PEBS Data Format
The PEBS record format for the 6th generation Intel Core processor is reporting with encoding 0011b in
IA32_PERF_CAPABILITIES[11:8]. The lay out is shown in Table 18-55. The PEBS record format, along with
debug/store area storage format, does not change regardless of whether IA-32e mode is active or not.
CPUID.01H:ECX.DTES64[bit 2] reports whether the processor's DS storage format support is mode-independent.
When set, it uses 64-bit DS storage format.
Vol. 3B 18-75
PERFORMANCE MONITORING
Table 18-55. PEBS Record Format for 6th Generation Intel Core Processor Family
Byte Offset
Field
Byte Offset
Field
00H
R/EFLAGS
68H
R11
08H
R/EIP
70H
R12
10H
R/EAX
78H
R13
18H
R/EBX
80H
R14
20H
R/ECX
88H
R15
28H
R/EDX
90H
Applicable Counter
30H
R/ESI
98H
Data Linear Address
38H
R/EDI
A0H
Data Source Encoding
40H
R/EBP
A8H
Latency value (core cycles)
48H
R/ESP
B0H
EventingIP
50H
R8
B8H
TX Abort Information (Section 18.11.5.1)
58H
R9
C0H
TSC
60H
R10
The layout of PEBS records are largely identical to those shown in Table 18-44.
The PEBS records at offsets 98H, A0H, and ABH record data gathered from three of the PEBS capabilities in prior
processor generations: load latency facility (Section 18.9.4.2), PDIR (Section 18.9.4.4), and data address profiling
(Section 18.11.3).
In the core PMU of the 6th generation processor, load latency facility and PDIR capabilities and data address
profiling are unchanged relative to the 4th and 5th generation Intel Core processors. Similarly, precise store is
replaced by data address profiling.
With format 0010b, a snapshot of the IA32_PERF_GLOBAL_STATUS may be useful to resolve the situations when
more than one of IA32_PMICx have been configured to collect PEBS data and two consecutive overflows of the
PEBS-enabled counters are sufficiently far apart in time. It is also possible for the image at 90H to indicate multiple
PEBS-enabled counters have overflowed. In the latter scenario, software cannot to correlate the PEBS record entry
to the multiple overflowed bits.
With PEBS record format encoding 0011b, offset 90H reports the “applicable counter” field, which is a multicounter PEBS resolution index allowing software to correlate the PEBS record entry with the eventing PEBS overflow when multiple counters are configured to record PEBS records. Additionally, offset C0H captures a snapshot of
the TSC that provides a time line annotation for each PEBS record entry.
18.13.1.2 PEBS Events
The list of precise events supported for PEBS in the Skylake microarchitecture is shown in Table 18-56.
18-76 Vol. 3B
PERFORMANCE MONITORING
Table 18-56. Precise Events for the Skylake Microarchitecture
Event Name
Event Select
INST_RETIRED
C0H
Sub-event
UMask
1
01H
PREC_DIST
2
ALL_CYCLES
01H
OTHER_ASSISTS
C1H
ANY
3FH
BR_INST_RETIRED
C4H
CONDITIONAL
01H
NEAR_CALL
02H
BR_MISP_RETIRED
C5H
ALL_BRANCHES
04H
NEAR_RETURN
08H
NEAR_TAKEN
20H
FAR_BRACHES
40H
CONDITIONAL
01H
ALL_BRANCHES
04H
NEAR_TAKEN
20H
3>
01H
FRONTEND_RETIRED
C6H
<Programmable
HLE_RETIRED
C8H
ABORTED
04H
RTM_RETIRED
C9H
ABORTED
04H
MEM_INST_RETIRED2
D0H
LOCK_LOADS
21H
SPLIT_LOADS
41H
MEM_LOAD_RETIRED
4
D1H
2
MEM_LOAD_L3_HIT_RETIRED
D2H
SPLIT_STORES
42H
ALL_LOADS
81H
ALL_STORES
82H
L1_HIT
01H
L2_HIT
02H
L3_HIT
04H
L1_MISS
08H
L2_MISS
10H
L3_MISS
20H
HIT_LFB
40H
XSNP_MISS
01H
XSNP_HIT
02H
XSNP_HITM
04H
XSNP_NONE
08H
NOTES:
1. Only available on IA32_PMC1.
2. INST_RETIRED.ALL_CYCLES is configured with additional parameters of cmask = 10 and INV = 1
3. Subevents are specified using MSR_PEBS_FRONTEND, see Section 18.13.2
4. Instruction with at least one load uop experiencing the condition specified in the UMask.
18.13.1.3 Data Address Profiling
The PEBS Data address profiling on the 6th generation Intel Core processor is largely unchanged from prior generation. When the DataLA facility is enabled, the relevant information written into a PEBS record affects entries at
offsets 98H, A0H and A8H, as shown in Table 18-46.
Vol. 3B 18-77
PERFORMANCE MONITORING
Table 18-57. Layout of Data Linear Address Information In PEBS Record
Field
Offset
Description
Data Linear
Address
98H
The linear address of the load or the destination of the store.
Store Status
A0H
• DCU Hit (Bit 0): The store hit the data cache closest to the core (L1 cache) if this bit is set, otherwise
the store missed the data cache. This information is valid only for the following store events:
UOPS_RETIRED.ALL (if store is tagged),
MEM_INST_RETIRED.STLB_MISS_STORES,
MEM_INST_RETIRED.ALL_STORES,
MEM_INST_RETIRED.SPLIT_STORES.
• Other bits are zero.
Reserved
A8H
Always zero.
18.13.1.4 PEBS Facility for Front End Events
In the 6th generation Intel Core processor, the PEBS facility has been extended to allow capturing PEBS data for
some microarchitectural conditions related to front end events. The frontend microarchitectural conditions
supported by PEBS requires the following interfaces:
•
The IA32_PERFEVTSELx MSR must select “FrontEnd_Retired” (C6H) in the EventSelect field (bits 7:0) and
umask = 01H,
•
The “FRONTEND_RETIRED” event employs a new MSR, MSR_PEBS_FRONTEND, to specify the supported
frontend event details, see Table 18-58.
•
Program the PEBS_EN_PMCx field of IA32_PEBS_ENABLE MSR as required.
Note the AnyThread field of IA32_PERFEVTSELx is ignored by the processor for the “FRONTEND_RETIRED” event.
The sub-event encodings supported by MSR_PEBS_FRONTEND.EVTSEL is given in Table 18-58.
Table 18-58. FrontEnd_Retired Sub-Event Encodings Supported by MSR_PEBS_FRONTEND.EVTSEL
Sub-Event Name
EVTSEL
Description
DSB_MISS
11H
Retired Instructions which experienced decode stream buffer (DSB) miss.
L1I_MISS
12H
The fetch of retired Instructions which experienced Instruction L1 Cache true miss1. Additional
requests to the same cache line as an in-flight L1I cache miss will not be counted.
L2_MISS
13H
The fetch of retired Instructions which experienced L2 Cache true miss. Additional requests to the
same cache line as an in-flight MLC cache miss will not be counted.
ITLB_MISS
14H
The fetch of retired Instructions which experienced ITLB true miss. Additional requests to the same
cache line as an in-flight ITLB miss will not be counted.
STLB_MISS
15H
The fetch of retired Instructions which experienced STLB true miss. Additional requests to the
same cache line as an in-flight STLB miss will not be counted.
IDQ_READ_BUBBLES
6H
An IDQ read bubble is defined as any one of the 4 allocation slots of IDQ that is not filled by the
front-end on any cycle where there is no back end stall. Using the threshold and latency fields in
MSR_PEBS_FRONTEND allows counting of IDQ read bubbles of various magnitude and duration.
Latency controls the number of cycles and Threshold controls the number of allocation slots that
contain bubbles.
The event counts if and only if a sequence of at least FE_LATENCY consecutive cycles contain at
least FE_TRESHOLD number of bubbles each.
NOTES:
1. A true miss is the first miss for a cacheline/page (excluding secondary misses that fall into same cacheline/page).
18-78 Vol. 3B
PERFORMANCE MONITORING
The layout of MSR_PEBS_FRONTEND is given in Table 18-59.
Table 18-59. MSR_PEBS_FRONTEND Layout
Bit Name
Offset
Description
EVTSEL
7:0
Encodes the sub-event within FrontEnd_Retired that can use PEBS facility, see Table 18-58
IDQ_Bubble_Length
19:8
Specifies the threshold of continuously elapsed cycles for the specified width of bubbles when
counting IDQ_READ_BUBBLES event
IDQ_Bubble_Width
22:20
Specifies the threshold of simultaneous bubbles when counting IDQ_READ_BUBBLES event
Reserved
63:23
Reserved
18.13.1.5 FRONTEND_RETIRED
The FRONTEND_RETIRED event is designed to help software developers identify exact instructions that caused
front-end issues. There are some instances in which the event will, by design, the under-counting scenarios include
the following:
•
The event counts only retired (non-speculative) Frontend events, i.e. events from just true program execution
path are counted.
•
The event will count once per cacheline (at most). If a cacheline contains multiple instructions which caused
front-end misses, the count will be only 1 for that line.
•
If the multibyte sequence of an instruction spans across two cachelines and causes a miss it will be recorded
once. If there were additional misses in the second cacheline, they will not be counted separately.
•
If a multi-uop instruction exceeds the allocation width of one cycle, the bubbles associated with these uops will
be counted once per that instruction.
•
If 2 instructions are fused (macro-fusion), and either of them or both cause front-end misses, it will be counted
once for the fused instruction.
•
If a frontend (miss) event occurs outside instruction boundary (e.g. due to processor handling of architectural
event), it may be reported for the next instruction to retire.
18.13.2 Off-core Response Performance Monitoring
The core PMU facility to collect off-core response events are similar to those described in Section 18.9.5. Each
event code for off-core response monitoring requires programming an associated configuration MSR,
MSR_OFFCORE_RSP_x. Software must program MSR_OFFCORE_RSP_x according to:
•
•
•
Transaction request type encoding (bits 15:0): see Table 18-60.
Supplier information (bits 30:16): see Table 18-61.
Snoop response information (bits 37:31): see Table 18-62.
Table 18-60. MSR_OFFCORE_RSP_x Request_Type Definition (Skylake microarchitecture)
Bit Name
Offset Description
DMND_DATA_RD
0
(R/W). Counts the number of demand data reads of full and partial cachelines as well as demand data
page table entry cacheline reads. Does not count hw or sw prefetches.
DMND_RFO
1
(R/W). Counts the number of demand reads for ownership (RFO) requests generated by a write to data
cacheline. Does not count L2 RFO prefetches.
DMND_IFETCH
2
(R/W). Counts the number of demand and DCU prefetch instruction cacheline reads. Does not count L2
code read prefetches.
Reserved
6:3
Reserved
PF_L3_DATA_RD
7
(R/W). Counts the number of MLC prefetches into L3.
Vol. 3B 18-79
PERFORMANCE MONITORING
Table 18-60. MSR_OFFCORE_RSP_x Request_Type Definition (Skylake microarchitecture) (Contd.)
Bit Name
Offset Description
PF_L3_RFO
8
Reserved
10:9
Reserved
STRM_ST
11
(R/W). Counts the number of streaming store requests.
Reserved
14:12
Reserved
OTHER
15
(R/W). Any other request that crosses IDI, including I/O.
(R/W). Counts the number of RFO requests generated by MLC prefetches to L3.
Table 18-61 lists the supplier information field that apply to 6th generation Intel Core processors. (CPUID signature
06_4EH, 06_5EH).
Table 18-61. MSR_OFFCORE_RSP_x Supplier Info Field Definition (CPUID Signature 06_4EH, 06_5EH)
Subtype
Bit Name
Offset
Description
Common
Any
16
(R/W). Catch all value for any response types.
Supplier
Info
NO_SUPP
17
(R/W). No Supplier Information available.
L3_HITM
18
(R/W). M-state initial lookup stat in L3.
L3_HITE
19
(R/W). E-state
L3_HITS
20
(R/W). S-state
Reserved
21
Reserved
L4_HIT
22
(R/W). L4 Cache (if L4 is present in the processor)
Reserved
25:23
Reserved
DRAM
26
(R/W). Local Node
Reserved
29:27
Reserved
SPL_HIT
30
(R/W). L4 cache super line hit (if L4 is present in the processor)
Table 18-62 lists the snoop information field that apply to processors with CPUID signature 06_4EH, 06_5EH.
18-80 Vol. 3B
PERFORMANCE MONITORING
Table 18-62. MSR_OFFCORE_RSP_x Snoop Info Field Definition (CPUID Signature 06_4EH, 06_5EH)
Subtype
Bit Name
Offset
Description
Snoop Info
SNOOP_NONE
31
(R/W). No details on snoop-related information
SNOOP_NOT_NEEDED
32
(R/W). No snoop was needed to satisfy the request.
SNOOP_MISS
33
(R/W). A snoop was needed and it missed all snooped caches:
-For LLC Hit, ReslHitl was returned by all cores
-For LLC Miss, Rspl was returned by all sockets and data was returned
from DRAM.
SNOOP_HIT_NO_FWD
34
(R/W). A snoop was needed and it hits in at least one snooped cache.
Hit denotes a cache-line was valid before snoop effect. This includes:
-Snoop Hit w/ Invalidation (LLC Hit, RFO)
-Snoop Hit, Left Shared (LLC Hit/Miss, IFetch/Data_RD)
-Snoop Hit w/ Invalidation and No Forward (LLC Miss, RFO Hit S)
In the LLC Miss case, data is returned from DRAM.
SNOOP_HIT_WITH_FWD
35
(R/W). A snoop was needed and data was forwarded from a remote
socket. This includes:
-Snoop Forward Clean, Left Shared (LLC Hit/Miss,
IFetch/Data_RD/RFT).
SNOOP_HITM
36
(R/W). A snoop was needed and it HitM-ed in local or remote cache.
HitM denotes a cache-line was in modified state before effect as a
results of snoop. This includes:
-Snoop HitM w/ WB (LLC miss, IFetch/Data_RD)
-Snoop Forward Modified w/ Invalidation (LLC Hit/Miss, RFO)
-Snoop MtoS (LLC Hit, IFetch/Data_RD).
SNOOP_NON_DRAM
18.14
37
(R/W). Target was non-DRAM system address. This includes MMIO
transactions.
PERFORMANCE MONITORING (PROCESSORS BASED ON INTEL NETBURST®
MICROARCHITECTURE)
The performance monitoring mechanism provided in processors based on Intel NetBurst microarchitecture is
different from that provided in the P6 family and Pentium processors. While the general concept of selecting,
filtering, counting, and reading performance events through the WRMSR, RDMSR, and RDPMC instructions is
unchanged, the setup mechanism and MSR layouts are incompatible with the P6 family and Pentium processor
mechanisms. Also, the RDPMC instruction has been extended to support faster reading of counters and to read all
performance counters available in processors based on Intel NetBurst microarchitecture.
The event monitoring mechanism consists of the following facilities:
•
The IA32_MISC_ENABLE MSR, which indicates the availability in an Intel 64 or IA-32 processor of the
performance monitoring and processor event-based sampling (PEBS) facilities.
•
Event selection control (ESCR) MSRs for selecting events to be monitored with specific performance counters.
The number available differs by family and model (43 to 45).
•
•
18 performance counter MSRs for counting events.
•
•
A debug store (DS) save area in memory for storing PEBS records.
18 counter configuration control (CCCR) MSRs, with one CCCR associated with each performance counter.
CCCRs sets up an associated performance counter for a specific method of counting.
The IA32_DS_AREA MSR, which establishes the location of the DS save area.
Vol. 3B 18-81
PERFORMANCE MONITORING
•
The debug store (DS) feature flag (bit 21) returned by the CPUID instruction, which indicates the availability of
the DS mechanism.
•
The MSR_PEBS_ENABLE MSR, which enables the PEBS facilities and replay tagging used in at-retirement event
counting.
•
A set of predefined events and event metrics that simplify the setting up of the performance counters to count
specific events.
Table 18-63 lists the performance counters and their associated CCCRs, along with the ESCRs that select events to
be counted for each performance counter. Predefined event metrics and events are listed in Chapter 19, “Performance-Monitoring Events.”
Table 18-63. Performance Counter MSRs and Associated CCCR and
ESCR MSRs (Processors Based on Intel NetBurst Microarchitecture)
Counter
CCCR
ESCR
Name
No.
Addr
Name
Addr
Name
No.
Addr
MSR_BPU_COUNTER0
0
300H
MSR_BPU_CCCR0
360H
MSR_BSU_ESCR0
MSR_FSB_ESCR0
MSR_MOB_ESCR0
MSR_PMH_ESCR0
MSR_BPU_ESCR0
MSR_IS_ESCR0
MSR_ITLB_ESCR0
MSR_IX_ESCR0
7
6
2
4
0
1
3
5
3A0H
3A2H
3AAH
3ACH
3B2H
3B4H
3B6H
3C8H
MSR_BPU_COUNTER1
1
301H
MSR_BPU_CCCR1
361H
MSR_BSU_ESCR0
MSR_FSB_ESCR0
MSR_MOB_ESCR0
MSR_PMH_ESCR0
MSR_BPU_ESCR0
MSR_IS_ESCR0
MSR_ITLB_ESCR0
MSR_IX_ESCR0
7
6
2
4
0
1
3
5
3A0H
3A2H
3AAH
3ACH
3B2H
3B4H
3B6H
3C8H
MSR_BPU_COUNTER2
2
302H
MSR_BPU_CCCR2
362H
MSR_BSU_ESCR1
MSR_FSB_ESCR1
MSR_MOB_ESCR1
MSR_PMH_ESCR1
MSR_BPU_ESCR1
MSR_IS_ESCR1
MSR_ITLB_ESCR1
MSR_IX_ESCR1
7
6
2
4
0
1
3
5
3A1H
3A3H
3ABH
3ADH
3B3H
3B5H
3B7H
3C9H
MSR_BPU_COUNTER3
3
303H
MSR_BPU_CCCR3
363H
MSR_BSU_ESCR1
MSR_FSB_ESCR1
MSR_MOB_ESCR1
MSR_PMH_ESCR1
MSR_BPU_ESCR1
MSR_IS_ESCR1
MSR_ITLB_ESCR1
MSR_IX_ESCR1
7
6
2
4
0
1
3
5
3A1H
3A3H
3ABH
3ADH
3B3H
3B5H
3B7H
3C9H
MSR_MS_COUNTER0
4
304H
MSR_MS_CCCR0
364H
MSR_MS_ESCR0
MSR_TBPU_ESCR0
MSR_TC_ESCR0
0
2
1
3C0H
3C2H
3C4H
MSR_MS_COUNTER1
5
305H
MSR_MS_CCCR1
365H
MSR_MS_ESCR0
MSR_TBPU_ESCR0
MSR_TC_ESCR0
0
2
1
3C0H
3C2H
3C4H
MSR_MS_COUNTER2
6
306H
MSR_MS_CCCR2
366H
MSR_MS_ESCR1
MSR_TBPU_ESCR1
MSR_TC_ESCR1
0
2
1
3C1H
3C3H
3C5H
MSR_MS_COUNTER3
7
307H
MSR_MS_CCCR3
367H
MSR_MS_ESCR1
MSR_TBPU_ESCR1
MSR_TC_ESCR1
0
2
1
3C1H
3C3H
3C5H
18-82 Vol. 3B
PERFORMANCE MONITORING
Table 18-63. Performance Counter MSRs and Associated CCCR and
ESCR MSRs (Processors Based on Intel NetBurst Microarchitecture) (Contd.)
Counter
CCCR
ESCR
Name
No.
Addr
Name
Addr
Name
No.
Addr
MSR_FLAME_COUNTER0
8
308H
MSR_FLAME_CCCR0
368H
MSR_FIRM_ESCR0
MSR_FLAME_ESCR0
MSR_DAC_ESCR0
MSR_SAAT_ESCR0
MSR_U2L_ESCR0
1
0
5
2
3
3A4H
3A6H
3A8H
3AEH
3B0H
MSR_FLAME_COUNTER1
9
309H
MSR_FLAME_CCCR1
369H
MSR_FIRM_ESCR0
MSR_FLAME_ESCR0
MSR_DAC_ESCR0
MSR_SAAT_ESCR0
MSR_U2L_ESCR0
1
0
5
2
3
3A4H
3A6H
3A8H
3AEH
3B0H
MSR_FLAME_COUNTER2
10
30AH
MSR_FLAME_CCCR2
36AH
MSR_FIRM_ESCR1
MSR_FLAME_ESCR1
MSR_DAC_ESCR1
MSR_SAAT_ESCR1
MSR_U2L_ESCR1
1
0
5
2
3
3A5H
3A7H
3A9H
3AFH
3B1H
MSR_FLAME_COUNTER3
11
30BH
MSR_FLAME_CCCR3
36BH
MSR_FIRM_ESCR1
MSR_FLAME_ESCR1
MSR_DAC_ESCR1
MSR_SAAT_ESCR1
MSR_U2L_ESCR1
1
0
5
2
3
3A5H
3A7H
3A9H
3AFH
3B1H
MSR_IQ_COUNTER0
12
30CH
MSR_IQ_CCCR0
36CH
MSR_CRU_ESCR0
MSR_CRU_ESCR2
MSR_CRU_ESCR4
MSR_IQ_ESCR01
MSR_RAT_ESCR0
MSR_SSU_ESCR0
MSR_ALF_ESCR0
4
5
6
0
2
3
1
3B8H
3CCH
3E0H
3BAH
3BCH
3BEH
3CAH
MSR_IQ_COUNTER1
13
30DH
MSR_IQ_CCCR1
36DH
MSR_CRU_ESCR0
MSR_CRU_ESCR2
MSR_CRU_ESCR4
MSR_IQ_ESCR01
MSR_RAT_ESCR0
MSR_SSU_ESCR0
MSR_ALF_ESCR0
4
5
6
0
2
3
1
3B8H
3CCH
3E0H
3BAH
3BCH
3BEH
3CAH
MSR_IQ_COUNTER2
14
30EH
MSR_IQ_CCCR2
36EH
MSR_CRU_ESCR1
MSR_CRU_ESCR3
MSR_CRU_ESCR5
MSR_IQ_ESCR11
MSR_RAT_ESCR1
MSR_ALF_ESCR1
4
5
6
0
2
1
3B9H
3CDH
3E1H
3BBH
3BDH
3CBH
MSR_IQ_COUNTER3
15
30FH
MSR_IQ_CCCR3
36FH
MSR_CRU_ESCR1
MSR_CRU_ESCR3
MSR_CRU_ESCR5
MSR_IQ_ESCR11
MSR_RAT_ESCR1
MSR_ALF_ESCR1
4
5
6
3B9H
3CDH
3E1H
3BBH
3BDH
3CBH
MSR_CRU_ESCR0
MSR_CRU_ESCR2
MSR_CRU_ESCR4
MSR_IQ_ESCR01
MSR_RAT_ESCR0
MSR_SSU_ESCR0
MSR_ALF_ESCR0
4
5
6
0
2
3
1
MSR_IQ_COUNTER4
16
310H
MSR_IQ_CCCR4
370H
2
1
0
3B8H
3CCH
3E0H
3BAH
3BCH
3BEH
3CAH
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PERFORMANCE MONITORING
Table 18-63. Performance Counter MSRs and Associated CCCR and
ESCR MSRs (Processors Based on Intel NetBurst Microarchitecture) (Contd.)
Counter
CCCR
ESCR
Name
No.
Addr
Name
Addr
Name
No.
Addr
MSR_IQ_COUNTER5
17
311H
MSR_IQ_CCCR5
371H
MSR_CRU_ESCR1
MSR_CRU_ESCR3
MSR_CRU_ESCR5
MSR_IQ_ESCR11
MSR_RAT_ESCR1
MSR_ALF_ESCR1
4
5
6
0
2
1
3B9H
3CDH
3E1H
3BBH
3BDH
3CBH
NOTES:
1. MSR_IQ_ESCR0 and MSR_IQ_ESCR1 are available only on early processor builds (family 0FH, models 01H-02H). These MSRs are not
available on later versions.
The types of events that can be counted with these performance monitoring facilities are divided into two classes:
non-retirement events and at-retirement events.
•
Non-retirement events (see Table 19-28) are events that occur any time during instruction execution (such as
bus transactions or cache transactions).
•
At-retirement events (see Table 19-29) are events that are counted at the retirement stage of instruction
execution, which allows finer granularity in counting events and capturing machine state.
The at-retirement counting mechanism includes facilities for tagging μops that have encountered a particular
performance event during instruction execution. Tagging allows events to be sorted between those that
occurred on an execution path that resulted in architectural state being committed at retirement as well as
events that occurred on an execution path where the results were eventually cancelled and never committed to
architectural state (such as, the execution of a mispredicted branch).
The Pentium 4 and Intel Xeon processor performance monitoring facilities support the three usage models
described below. The first two models can be used to count both non-retirement and at-retirement events; the
third model is used to count a subset of at-retirement events:
•
Event counting — A performance counter is configured to count one or more types of events. While the
counter is counting, software reads the counter at selected intervals to determine the number of events that
have been counted between the intervals.
•
Interrupt-based event sampling — A performance counter is configured to count one or more types of
events and to generate an interrupt when it overflows. To trigger an overflow, the counter is preset to a
modulus value that will cause the counter to overflow after a specific number of events have been counted.
When the counter overflows, the processor generates a performance monitoring interrupt (PMI). The interrupt
service routine for the PMI then records the return instruction pointer (RIP), resets the modulus, and restarts
the counter. Code performance can be analyzed by examining the distribution of RIPs with a tool like the
VTune™ Performance Analyzer.
•
Processor event-based sampling (PEBS) — In PEBS, the processor writes a record of the architectural
state of the processor to a memory buffer after the counter overflows. The records of architectural state
provide additional information for use in performance tuning. Processor-based event sampling can be used to
count only a subset of at-retirement events. PEBS captures more precise processor state information compared
to interrupt based event sampling, because the latter need to use the interrupt service routine to re-construct
the architectural states of processor.
The following sections describe the MSRs and data structures used for performance monitoring in the Pentium 4
and Intel Xeon processors.
18.14.1 ESCR MSRs
The 45 ESCR MSRs (see Table 18-63) allow software to select specific events to be countered. Each ESCR is usually
associated with a pair of performance counters (see Table 18-63) and each performance counter has several ESCRs
associated with it (allowing the events counted to be selected from a variety of events).
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Figure 18-43 shows the layout of an ESCR MSR. The functions of the flags and fields are:
•
USR flag, bit 2 — When set, events are counted when the processor is operating at a current privilege level
(CPL) of 1, 2, or 3. These privilege levels are generally used by application code and unprotected operating
system code.
•
OS flag, bit 3 — When set, events are counted when the processor is operating at CPL of 0. This privilege level
is generally reserved for protected operating system code. (When both the OS and USR flags are set, events
are counted at all privilege levels.)
31 30
25 24
Event
Select
5 4 3 2 1 0
9 8
Tag
Value
Event Mask
Tag Enable
OS
USR
Reserved
63
32
Reserved
Figure 18-43. Event Selection Control Register (ESCR) for Pentium 4
and Intel Xeon Processors without Intel HT Technology Support
•
Tag enable, bit 4 — When set, enables tagging of μops to assist in at-retirement event counting; when clear,
disables tagging. See Section 18.14.6, “At-Retirement Counting.”
•
Tag value field, bits 5 through 8 — Selects a tag value to associate with a μop to assist in at-retirement
event counting.
•
Event mask field, bits 9 through 24 — Selects events to be counted from the event class selected with the
event select field.
•
Event select field, bits 25 through 30) — Selects a class of events to be counted. The events within this
class that are counted are selected with the event mask field.
When setting up an ESCR, the event select field is used to select a specific class of events to count, such as retired
branches. The event mask field is then used to select one or more of the specific events within the class to be
counted. For example, when counting retired branches, four different events can be counted: branch not taken
predicted, branch not taken mispredicted, branch taken predicted, and branch taken mispredicted. The OS and
USR flags allow counts to be enabled for events that occur when operating system code and/or application code are
being executed. If neither the OS nor USR flag is set, no events will be counted.
The ESCRs are initialized to all 0s on reset. The flags and fields of an ESCR are configured by writing to the ESCR
using the WRMSR instruction. Table 18-63 gives the addresses of the ESCR MSRs.
Writing to an ESCR MSR does not enable counting with its associated performance counter; it only selects the event
or events to be counted. The CCCR for the selected performance counter must also be configured. Configuration of
the CCCR includes selecting the ESCR and enabling the counter.
18.14.2 Performance Counters
The performance counters in conjunction with the counter configuration control registers (CCCRs) are used for
filtering and counting the events selected by the ESCRs. Processors based on Intel NetBurst microarchitecture
provide 18 performance counters organized into 9 pairs. A pair of performance counters is associated with a particular subset of events and ESCR’s (see Table 18-63). The counter pairs are partitioned into four groups:
•
The BPU group, includes two performance counter pairs:
— MSR_BPU_COUNTER0 and MSR_BPU_COUNTER1.
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PERFORMANCE MONITORING
— MSR_BPU_COUNTER2 and MSR_BPU_COUNTER3.
•
The MS group, includes two performance counter pairs:
— MSR_MS_COUNTER0 and MSR_MS_COUNTER1.
— MSR_MS_COUNTER2 and MSR_MS_COUNTER3.
•
The FLAME group, includes two performance counter pairs:
— MSR_FLAME_COUNTER0 and MSR_FLAME_COUNTER1.
— MSR_FLAME_COUNTER2 and MSR_FLAME_COUNTER3.
•
The IQ group, includes three performance counter pairs:
— MSR_IQ_COUNTER0 and MSR_IQ_COUNTER1.
— MSR_IQ_COUNTER2 and MSR_IQ_COUNTER3.
— MSR_IQ_COUNTER4 and MSR_IQ_COUNTER5.
The MSR_IQ_COUNTER4 counter in the IQ group provides support for the PEBS.
Alternate counters in each group can be cascaded: the first counter in one pair can start the first counter in the
second pair and vice versa. A similar cascading is possible for the second counters in each pair. For example, within
the BPU group of counters, MSR_BPU_COUNTER0 can start MSR_BPU_COUNTER2 and vice versa, and
MSR_BPU_COUNTER1 can start MSR_BPU_COUNTER3 and vice versa (see Section 18.14.5.6, “Cascading Counters”). The cascade flag in the CCCR register for the performance counter enables the cascading of counters.
Each performance counter is 40-bits wide (see Figure 18-44). The RDPMC instruction is intended to allow reading
of either the full counter-width (40-bits) or the low 32-bits of the counter. Reading the low 32-bits is faster than
reading the full counter width and is appropriate in situations where the count is small enough to be contained in
32 bits.
The RDPMC instruction can be used by programs or procedures running at any privilege level and in virtual-8086
mode to read these counters. The PCE flag in control register CR4 (bit 8) allows the use of this instruction to be
restricted to only programs and procedures running at privilege level 0.
31
0
Counter
63
32
39
Reserved
Counter
Figure 18-44. Performance Counter (Pentium 4 and Intel Xeon Processors)
The RDPMC instruction is not serializing or ordered with other instructions. Thus, it does not necessarily wait until
all previous instructions have been executed before reading the counter. Similarly, subsequent instructions may
begin execution before the RDPMC instruction operation is performed.
Only the operating system, executing at privilege level 0, can directly manipulate the performance counters, using
the RDMSR and WRMSR instructions. A secure operating system would clear the PCE flag during system initialization to disable direct user access to the performance-monitoring counters, but provide a user-accessible programming interface that emulates the RDPMC instruction.
Some uses of the performance counters require the counters to be preset before counting begins (that is, before
the counter is enabled). This can be accomplished by writing to the counter using the WRMSR instruction. To set a
counter to a specified number of counts before overflow, enter a 2s complement negative integer in the counter.
The counter will then count from the preset value up to -1 and overflow. Writing to a performance counter in a
Pentium 4 or Intel Xeon processor with the WRMSR instruction causes all 40 bits of the counter to be written.
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PERFORMANCE MONITORING
18.14.3 CCCR MSRs
Each of the 18 performance counters has one CCCR MSR associated with it (see Table 18-63). The CCCRs control
the filtering and counting of events as well as interrupt generation. Figure 18-45 shows the layout of an CCCR MSR.
The functions of the flags and fields are as follows:
•
Enable flag, bit 12 — When set, enables counting; when clear, the counter is disabled. This flag is cleared on
reset.
•
ESCR select field, bits 13 through 15 — Identifies the ESCR to be used to select events to be counted with
the counter associated with the CCCR.
•
Compare flag, bit 18 — When set, enables filtering of the event count; when clear, disables filtering. The
filtering method is selected with the threshold, complement, and edge flags.
•
Complement flag, bit 19 — Selects how the incoming event count is compared with the threshold value.
When set, event counts that are less than or equal to the threshold value result in a single count being
delivered to the performance counter; when clear, counts greater than the threshold value result in a count
being delivered to the performance counter (see Section 18.14.5.2, “Filtering Events”). The complement flag is
not active unless the compare flag is set.
•
Threshold field, bits 20 through 23 — Selects the threshold value to be used for comparisons. The
processor examines this field only when the compare flag is set, and uses the complement flag setting to
determine the type of threshold comparison to be made. The useful range of values that can be entered in this
field depend on the type of event being counted (see Section 18.14.5.2, “Filtering Events”).
•
Edge flag, bit 24 — When set, enables rising edge (false-to-true) edge detection of the threshold comparison
output for filtering event counts; when clear, rising edge detection is disabled. This flag is active only when the
compare flag is set.
Reserved
31 30 29
27 26 25 24 23
20 19 18 17 16 15
Threshold
13 12 11
ESCR
Select
0
Reserved
Reserved
Enable
Reserved: Must be set to 11B
Compare
Complement
Edge
FORCE_OVF
OVF_PMI
Cascade
OVF
63
32
Reserved
Figure 18-45. Counter Configuration Control Register (CCCR)
•
FORCE_OVF flag, bit 25 — When set, forces a counter overflow on every counter increment; when clear,
overflow only occurs when the counter actually overflows.
•
OVF_PMI flag, bit 26 — When set, causes a performance monitor interrupt (PMI) to be generated when the
counter overflows occurs; when clear, disables PMI generation. Note that the PMI is generated on the next
event count after the counter has overflowed.
•
Cascade flag, bit 30 — When set, enables counting on one counter of a counter pair when its alternate
counter in the other the counter pair in the same counter group overflows (see Section 18.14.2, “Performance
Counters,” for further details); when clear, disables cascading of counters.
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PERFORMANCE MONITORING
•
OVF flag, bit 31 — Indicates that the counter has overflowed when set. This flag is a sticky flag that must be
explicitly cleared by software.
The CCCRs are initialized to all 0s on reset.
The events that an enabled performance counter actually counts are selected and filtered by the following flags and
fields in the ESCR and CCCR registers and in the qualification order given:
1. The event select and event mask fields in the ESCR select a class of events to be counted and one or more
event types within the class, respectively.
2. The OS and USR flags in the ESCR selected the privilege levels at which events will be counted.
3. The ESCR select field of the CCCR selects the ESCR. Since each counter has several ESCRs associated with it,
one ESCR must be chosen to select the classes of events that may be counted.
4. The compare and complement flags and the threshold field of the CCCR select an optional threshold to be used
in qualifying an event count.
5. The edge flag in the CCCR allows events to be counted only on rising-edge transitions.
The qualification order in the above list implies that the filtered output of one “stage” forms the input for the next.
For instance, events filtered using the privilege level flags can be further qualified by the compare and complement
flags and the threshold field, and an event that matched the threshold criteria, can be further qualified by edge
detection.
The uses of the flags and fields in the CCCRs are discussed in greater detail in Section 18.14.5, “Programming the
Performance Counters for Non-Retirement Events.”
18.14.4 Debug Store (DS) Mechanism
The debug store (DS) mechanism was introduced with processors based on Intel NetBurst microarchitecture to
allow various types of information to be collected in memory-resident buffers for use in debugging and tuning
programs. The DS mechanism can be used to collect two types of information: branch records and processor eventbased sampling (PEBS) records. The availability of the DS mechanism in a processor is indicated with the DS
feature flag (bit 21) returned by the CPUID instruction.
See Section 17.4.5, “Branch Trace Store (BTS),” and Section 18.14.7, “Processor Event-Based Sampling (PEBS),”
for a description of these facilities. Records collected with the DS mechanism are saved in the DS save area. See
Section 17.4.9, “BTS and DS Save Area.”
18.14.5 Programming the Performance Counters
for Non-Retirement Events
The basic steps to program a performance counter and to count events include the following:
1. Select the event or events to be counted.
2. For each event, select an ESCR that supports the event using the values in the ESCR restrictions row in Table
19-28, Chapter 19.
3. Match the CCCR Select value and ESCR name in Table 19-28 to a value listed in Table 18-63; select a CCCR and
performance counter.
4. Set up an ESCR for the specific event or events to be counted and the privilege levels at which the are to be
counted.
5. Set up the CCCR for the performance counter by selecting the ESCR and the desired event filters.
6. Set up the CCCR for optional cascading of event counts, so that when the selected counter overflows its
alternate counter starts.
7. Set up the CCCR to generate an optional performance monitor interrupt (PMI) when the counter overflows. If
PMI generation is enabled, the local APIC must be set up to deliver the interrupt to the processor and a handler
for the interrupt must be in place.
8. Enable the counter to begin counting.
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PERFORMANCE MONITORING
18.14.5.1 Selecting Events to Count
Table 19-29 in Chapter 19 lists a set of at-retirement events for processors based on Intel NetBurst microarchitecture. For each event listed in Table 19-29, setup information is provided. Table 18-64 gives an example of one of
the events.
Table 18-64. Event Example
Event Name
Event Parameters
Parameter Value Description
branch_retired
Counts the retirement of a branch. Specify one or more mask bits to select
any combination of branch taken, not-taken, predicted and mispredicted.
ESCR restrictions
MSR_CRU_ESCR2
MSR_CRU_ESCR3
See Table 15-3 for the addresses of the ESCR MSRs.
Counter numbers per ESCR2: 12, 13, 16 The counter numbers associated with each ESCR are provided. The
ESCR
ESCR3: 14, 15, 17 performance counters and corresponding CCCRs can be obtained from
Table 15-3.
ESCR Event Select
06H
ESCR[24:9]
ESCR Event Mask
Bit 0: MMNP
CCCR Select
ESCR[31:25]
Branch Not-taken Mispredicted
2: MMTP
Branch Taken Predicted
3: MMTM
Branch Taken Mispredicted
05H
Event Specific Notes
Branch Not-taken Predicted
1: MMNM
CCCR[15:13]
P6: EMON_BR_INST_RETIRED
Can Support PEBS
No
Requires Additional
MSRs for Tagging
No
For Table 19-28 and Table 19-29, Chapter 19, the name of the event is listed in the Event Name column and parameters that define the event and other information are listed in the Event Parameters column. The Parameter Value
and Description columns give specific parameters for the event and additional description information. Entries in
the Event Parameters column are described below.
•
ESCR restrictions — Lists the ESCRs that can be used to program the event. Typically only one ESCR is
needed to count an event.
•
Counter numbers per ESCR — Lists which performance counters are associated with each ESCR. Table 18-63
gives the name of the counter and CCCR for each counter number. Typically only one counter is needed to count
the event.
•
•
ESCR event select — Gives the value to be placed in the event select field of the ESCR to select the event.
ESCR event mask — Gives the value to be placed in the Event Mask field of the ESCR to select sub-events to
be counted. The parameter value column defines the documented bits with relative bit position offset starting
from 0, where the absolute bit position of relative offset 0 is bit 9 of the ESCR. All undocumented bits are
reserved and should be set to 0.
•
CCCR select — Gives the value to be placed in the ESCR select field of the CCCR associated with the counter
to select the ESCR to be used to define the event. This value is not the address of the ESCR; it is the number of
the ESCR from the Number column in Table 18-63.
•
Event specific notes — Gives additional information about the event, such as the name of the same or a
similar event defined for the P6 family processors.
•
Can support PEBS — Indicates if PEBS is supported for the event (only supplied for at-retirement events
listed in Table 19-29.)
•
Requires additional MSR for tagging — Indicates which if any additional MSRs must be programmed to
count the events (only supplied for the at-retirement events listed in Table 19-29.)
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PERFORMANCE MONITORING
NOTE
The performance-monitoring events listed in Chapter 19, “Performance-Monitoring Events,” are
intended to be used as guides for performance tuning. The counter values reported are not
guaranteed to be absolutely accurate and should be used as a relative guide for tuning. Known
discrepancies are documented where applicable.
The following procedure shows how to set up a performance counter for basic counting; that is, the counter is set
up to count a specified event indefinitely, wrapping around whenever it reaches its maximum count. This procedure
is continued through the following four sections.
Using information in Table 19-28, Chapter 19, an event to be counted can be selected as follows:
1. Select the event to be counted.
2. Select the ESCR to be used to select events to be counted from the ESCRs field.
3. Select the number of the counter to be used to count the event from the Counter Numbers Per ESCR field.
4. Determine the name of the counter and the CCCR associated with the counter, and determine the MSR
addresses of the counter, CCCR, and ESCR from Table 18-63.
5. Use the WRMSR instruction to write the ESCR Event Select and ESCR Event Mask values into the appropriate
fields in the ESCR. At the same time set or clear the USR and OS flags in the ESCR as desired.
6. Use the WRMSR instruction to write the CCCR Select value into the appropriate field in the CCCR.
NOTE
Typically all the fields and flags of the CCCR will be written with one WRMSR instruction; however,
in this procedure, several WRMSR writes are used to more clearly demonstrate the uses of the
various CCCR fields and flags.
This setup procedure is continued in the next section, Section 18.14.5.2, “Filtering Events.”
18.14.5.2 Filtering Events
Each counter receives up to 4 input lines from the processor hardware from which it is counting events. The counter
treats these inputs as binary inputs (input 0 has a value of 1, input 1 has a value of 2, input 3 has a value of 4, and
input 3 has a value of 8). When a counter is enabled, it adds this binary input value to the counter value on each
clock cycle. For each clock cycle, the value added to the counter can then range from 0 (no event) to 15.
For many events, only the 0 input line is active, so the counter is merely counting the clock cycles during which the
0 input is asserted. However, for some events two or more input lines are used. Here, the counters threshold
setting can be used to filter events. The compare, complement, threshold, and edge fields control the filtering of
counter increments by input value.
If the compare flag is set, then a “greater than” or a “less than or equal to” comparison of the input value vs. a
threshold value can be made. The complement flag selects “less than or equal to” (flag set) or “greater than” (flag
clear). The threshold field selects a threshold value of from 0 to 15. For example, if the complement flag is cleared
and the threshold field is set to 6, than any input value of 7 or greater on the 4 inputs to the counter will cause the
counter to be incremented by 1, and any value less than 7 will cause an increment of 0 (or no increment) of the
counter. Conversely, if the complement flag is set, any value from 0 to 6 will increment the counter and any value
from 7 to 15 will not increment the counter. Note that when a threshold condition has been satisfied, the input to
the counter is always 1, not the input value that is presented to the threshold filter.
The edge flag provides further filtering of the counter inputs when a threshold comparison is being made. The edge
flag is only active when the compare flag is set. When the edge flag is set, the resulting output from the threshold
filter (a value of 0 or 1) is used as an input to the edge filter. Each clock cycle, the edge filter examines the last and
current input values and sends a count to the counter only when it detects a “rising edge” event; that is, a false-totrue transition. Figure 18-46 illustrates rising edge filtering.
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PERFORMANCE MONITORING
The following procedure shows how to configure a CCCR to filter events using the threshold filter and the edge
filter. This procedure is a continuation of the setup procedure introduced in Section 18.14.5.1, “Selecting Events to
Count.”
7. (Optional) To set up the counter for threshold filtering, use the WRMSR instruction to write values in the CCCR
compare and complement flags and the threshold field:
— Set the compare flag.
— Set or clear the complement flag for less than or equal to or greater than comparisons, respectively.
— Enter a value from 0 to 15 in the threshold field.
8. (Optional) Select rising edge filtering by setting the CCCR edge flag.
This setup procedure is continued in the next section, Section 18.14.5.3, “Starting Event Counting.”
Processor Clock
Output from
Threshold Filter
Counter Increments
On Rising Edge
(False-to-True)
Figure 18-46. Effects of Edge Filtering
18.14.5.3 Starting Event Counting
Event counting by a performance counter can be initiated in either of two ways. The typical way is to set the enable
flag in the counter’s CCCR. Following the instruction to set the enable flag, event counting begins and continues
until it is stopped (see Section 18.14.5.5, “Halting Event Counting”).
The following procedural step shows how to start event counting. This step is a continuation of the setup procedure
introduced in Section 18.14.5.2, “Filtering Events.”
9. To start event counting, use the WRMSR instruction to set the CCCR enable flag for the performance counter.
This setup procedure is continued in the next section, Section 18.14.5.4, “Reading a Performance Counter’s
Count.”
The second way that a counter can be started by using the cascade feature. Here, the overflow of one counter automatically starts its alternate counter (see Section 18.14.5.6, “Cascading Counters”).
18.14.5.4 Reading a Performance Counter’s Count
Performance counters can be read using either the RDPMC or RDMSR instructions. The enhanced functions of the
RDPMC instruction (including fast read) are described in Section 18.14.2, “Performance Counters.” These instructions can be used to read a performance counter while it is counting or when it is stopped.
The following procedural step shows how to read the event counter. This step is a continuation of the setup procedure introduced in Section 18.14.5.3, “Starting Event Counting.”
10. To read a performance counters current event count, execute the RDPMC instruction with the counter number
obtained from Table 18-63 used as an operand.
This setup procedure is continued in the next section, Section 18.14.5.5, “Halting Event Counting.”
18.14.5.5 Halting Event Counting
After a performance counter has been started (enabled), it continues counting indefinitely. If the counter overflows
(goes one count past its maximum count), it wraps around and continues counting. When the counter wraps
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around, it sets its OVF flag to indicate that the counter has overflowed. The OVF flag is a sticky flag that indicates
that the counter has overflowed at least once since the OVF bit was last cleared.
To halt counting, the CCCR enable flag for the counter must be cleared.
The following procedural step shows how to stop event counting. This step is a continuation of the setup procedure
introduced in Section 18.14.5.4, “Reading a Performance Counter’s Count.”
11. To stop event counting, execute a WRMSR instruction to clear the CCCR enable flag for the performance
counter.
To halt a cascaded counter (a counter that was started when its alternate counter overflowed), either clear the
Cascade flag in the cascaded counter’s CCCR MSR or clear the OVF flag in the alternate counter’s CCCR MSR.
18.14.5.6 Cascading Counters
As described in Section 18.14.2, “Performance Counters,” eighteen performance counters are implemented in
pairs. Nine pairs of counters and associated CCCRs are further organized as four blocks: BPU, MS, FLAME, and IQ
(see Table 18-63). The first three blocks contain two pairs each. The IQ block contains three pairs of counters (12
through 17) with associated CCCRs (MSR_IQ_CCCR0 through MSR_IQ_CCCR5).
The first 8 counter pairs (0 through 15) can be programmed using ESCRs to detect performance monitoring events.
Pairs of ESCRs in each of the four blocks allow many different types of events to be counted. The cascade flag in the
CCCR MSR allows nested monitoring of events to be performed by cascading one counter to a second counter
located in another pair in the same block (see Figure 18-45 for the location of the flag).
Counters 0 and 1 form the first pair in the BPU block. Either counter 0 or 1 can be programmed to detect an event
via MSR_MO B_ESCR0. Counters 0 and 2 can be cascaded in any order, as can counters 1 and 3. It’s possible to set
up 4 counters in the same block to cascade on two pairs of independent events. The pairing described also applies
to subsequent blocks. Since the IQ PUB has two extra counters, cascading operates somewhat differently if 16 and
17 are involved. In the IQ block, counter 16 can only be cascaded from counter 14 (not from 12); counter 14
cannot be cascaded from counter 16 using the CCCR cascade bit mechanism. Similar restrictions apply to counter
17.
Example 18-1. Counting Events
Assume a scenario where counter X is set up to count 200 occurrences of event A; then counter Y is set up to count
400 occurrences of event B. Each counter is set up to count a specific event and overflow to the next counter. In the
above example, counter X is preset for a count of -200 and counter Y for a count of -400; this setup causes the
counters to overflow on the 200th and 400th counts respectively.
Continuing this scenario, counter X is set up to count indefinitely and wraparound on overflow. This is described in
the basic performance counter setup procedure that begins in Section 18.14.5.1, “Selecting Events to Count.”
Counter Y is set up with the cascade flag in its associated CCCR MSR set to 1 and its enable flag set to 0.
To begin the nested counting, the enable bit for the counter X is set. Once enabled, counter X counts until it overflows. At this point, counter Y is automatically enabled and begins counting. Thus counter X overflows after 200
occurrences of event A. Counter Y then starts, counting 400 occurrences of event B before overflowing. When
performance counters are cascaded, the counter Y would typically be set up to generate an interrupt on overflow.
This is described in Section 18.14.5.8, “Generating an Interrupt on Overflow.”
The cascading counters mechanism can be used to count a single event. The counting begins on one counter then
continues on the second counter after the first counter overflows. This technique doubles the number of event
counts that can be recorded, since the contents of the two counters can be added together.
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18.14.5.7 EXTENDED CASCADING
Extended cascading is a model-specific feature in the Intel NetBurst microarchitecture with CPUID
DisplayFamily_DisplayModel 0F_02, 0F_03, 0F_04, 0F_06. This feature uses bit 11 in CCCRs associated with the IQ
block. See Table 18-65.
Table 18-65. CCR Names and Bit Positions
CCCR Name:Bit Position
Bit Name
Description
MSR_IQ_CCCR1|2:11
Reserved
MSR_IQ_CCCR0:11
CASCNT4INTO0
Allow counter 4 to cascade into counter 0
MSR_IQ_CCCR3:11
CASCNT5INTO3
Allow counter 5 to cascade into counter 3
MSR_IQ_CCCR4:11
CASCNT5INTO4
Allow counter 5 to cascade into counter 4
MSR_IQ_CCCR5:11
CASCNT4INTO5
Allow counter 4 to cascade into counter 5
The extended cascading feature can be adapted to the Interrupt based sampling usage model for performance
monitoring. However, it is known that performance counters do not generate PMI in cascade mode or extended
cascade mode due to an erratum. This erratum applies to processors with CPUID DisplayFamily_DisplayModel
signature of 0F_02. For processors with CPUID DisplayFamily_DisplayModel signature of 0F_00 and 0F_01, the
erratum applies to processors with stepping encoding greater than 09H.
Counters 16 and 17 in the IQ block are frequently used in processor event-based sampling or at-retirement
counting of events indicating a stalled condition in the pipeline. Neither counter 16 or 17 can initiate the cascading
of counter pairs using the cascade bit in a CCCR.
Extended cascading permits performance monitoring tools to use counters 16 and 17 to initiate cascading of two
counters in the IQ block. Extended cascading from counter 16 and 17 is conceptually similar to cascading other
counters, but instead of using CASCADE bit of a CCCR, one of the four CASCNTxINTOy bits is used.
Example 18-2. Scenario for Extended Cascading
A usage scenario for extended cascading is to sample instructions retired on logical processor 1 after the first 4096
instructions retired on logical processor 0. A procedure to program extended cascading in this scenario is outlined
below:
1. Write the value 0 to counter 12.
2. Write the value 04000603H to MSR_CRU_ESCR0 (corresponding to selecting the NBOGNTAG and NBOGTAG
event masks with qualification restricted to logical processor 1).
3. Write the value 04038800H to MSR_IQ_CCCR0. This enables CASCNT4INTO0 and OVF_PMI. An ISR can sample
on instruction addresses in this case (do not set ENABLE, or CASCADE).
4. Write the value FFFFF000H into counter 16.1.
5. Write the value 0400060CH to MSR_CRU_ESCR2 (corresponding to selecting the NBOGNTAG and NBOGTAG
event masks with qualification restricted to logical processor 0).
6. Write the value 00039000H to MSR_IQ_CCCR4 (set ENABLE bit, but not OVF_PMI).
Another use for cascading is to locate stalled execution in a multithreaded application. Assume MOB replays in
thread B cause thread A to stall. Getting a sample of the stalled execution in this scenario could be accomplished
by:
1. Set up counter B to count MOB replays on thread B.
2. Set up counter A to count resource stalls on thread A; set its force overflow bit and the appropriate CASCNTxINTOy bit.
3. Use the performance monitoring interrupt to capture the program execution data of the stalled thread.
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18.14.5.8 Generating an Interrupt on Overflow
Any performance counter can be configured to generate a performance monitor interrupt (PMI) if the counter overflows. The PMI interrupt service routine can then collect information about the state of the processor or program
when overflow occurred. This information can then be used with a tool like the Intel® VTune™ Performance
Analyzer to analyze and tune program performance.
To enable an interrupt on counter overflow, the OVR_PMI flag in the counter’s associated CCCR MSR must be set.
When overflow occurs, a PMI is generated through the local APIC. (Here, the performance counter entry in the local
vector table [LVT] is set up to deliver the interrupt generated by the PMI to the processor.)
The PMI service routine can use the OVF flag to determine which counter overflowed when multiple counters have
been configured to generate PMIs. Also, note that these processors mask PMIs upon receiving an interrupt. Clear
this condition before leaving the interrupt handler.
When generating interrupts on overflow, the performance counter being used should be preset to value that will
cause an overflow after a specified number of events are counted plus 1. The simplest way to select the preset
value is to write a negative number into the counter, as described in Section 18.14.5.6, “Cascading Counters.”
Here, however, if an interrupt is to be generated after 100 event counts, the counter should be preset to minus 100
plus 1 (-100 + 1), or -99. The counter will then overflow after it counts 99 events and generate an interrupt on the
next (100th) event counted. The difference of 1 for this count enables the interrupt to be generated immediately
after the selected event count has been reached, instead of waiting for the overflow to be propagation through the
counter.
Because of latency in the microarchitecture between the generation of events and the generation of interrupts on
overflow, it is sometimes difficult to generate an interrupt close to an event that caused it. In these situations, the
FORCE_OVF flag in the CCCR can be used to improve reporting. Setting this flag causes the counter to overflow on
every counter increment, which in turn triggers an interrupt after every counter increment.
18.14.5.9 Counter Usage Guideline
There are some instances where the user must take care to configure counting logic properly, so that it is not
powered down. To use any ESCR, even when it is being used just for tagging, (any) one of the counters that the
particular ESCR (or its paired ESCR) can be connected to should be enabled. If this is not done, 0 counts may
result. Likewise, to use any counter, there must be some event selected in a corresponding ESCR (other than
no_event, which generally has a select value of 0).
18.14.6 At-Retirement Counting
At-retirement counting provides a means counting only events that represent work committed to architectural
state and ignoring work that was performed speculatively and later discarded.
One example of this speculative activity is branch prediction. When a branch misprediction occurs, the results of
instructions that were decoded and executed down the mispredicted path are canceled. If a performance counter
was set up to count all executed instructions, the count would include instructions whose results were canceled as
well as those whose results committed to architectural state.
To provide finer granularity in event counting in these situations, the performance monitoring facilities provided in
the Pentium 4 and Intel Xeon processors provide a mechanism for tagging events and then counting only those
tagged events that represent committed results. This mechanism is called “at-retirement counting.”
Tables 19-29 through 19-33 list predefined at-retirement events and event metrics that can be used to for tagging
events when using at retirement counting. The following terminology is used in describing at-retirement counting:
•
Bogus, non-bogus, retire — In at-retirement event descriptions, the term “bogus” refers to instructions or
μops that must be canceled because they are on a path taken from a mispredicted branch. The terms “retired”
and “non-bogus” refer to instructions or μops along the path that results in committed architectural state
changes as required by the program being executed. Thus instructions and μops are either bogus or non-bogus,
but not both. Several of the Pentium 4 and Intel Xeon processors’ performance monitoring events (such as,
Instruction_Retired and Uops_Retired in Table 19-29) can count instructions or μops that are retired based on
the characterization of bogus” versus non-bogus.
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PERFORMANCE MONITORING
•
Tagging — Tagging is a means of marking μops that have encountered a particular performance event so they
can be counted at retirement. During the course of execution, the same event can happen more than once per
μop and a direct count of the event would not provide an indication of how many μops encountered that event.
The tagging mechanisms allow a μop to be tagged once during its lifetime and thus counted once at retirement.
The retired suffix is used for performance metrics that increment a count once per μop, rather than once per
event. For example, a μop may encounter a cache miss more than once during its life time, but a “Miss Retired”
metric (that counts the number of retired μops that encountered a cache miss) will increment only once for that
μop. A “Miss Retired” metric would be useful for characterizing the performance of the cache hierarchy for a
particular instruction sequence. Details of various performance metrics and how these can be constructed
using the Pentium 4 and Intel Xeon processors performance events are provided in the Intel Pentium 4
Processor Optimization Reference Manual (see Section 1.4, “Related Literature”).
•
Replay — To maximize performance for the common case, the Intel NetBurst microarchitecture aggressively
schedules μops for execution before all the conditions for correct execution are guaranteed to be satisfied. In
the event that all of these conditions are not satisfied, μops must be reissued. The mechanism that the Pentium
4 and Intel Xeon processors use for this reissuing of μops is called replay. Some examples of replay causes are
cache misses, dependence violations, and unforeseen resource constraints. In normal operation, some number
of replays is common and unavoidable. An excessive number of replays is an indication of a performance
problem.
•
Assist — When the hardware needs the assistance of microcode to deal with some event, the machine takes
an assist. One example of this is an underflow condition in the input operands of a floating-point operation. The
hardware must internally modify the format of the operands in order to perform the computation. Assists clear
the entire machine of μops before they begin and are costly.
18.14.6.1 Using At-Retirement Counting
Processors based on Intel NetBurst microarchitecture allow counting both events and μops that encountered a
specified event. For a subset of the at-retirement events listed in Table 19-29, a μop may be tagged when it
encounters that event. The tagging mechanisms can be used in Interrupt-based event sampling, and a subset of
these mechanisms can be used in PEBS. There are four independent tagging mechanisms, and each mechanism
uses a different event to count μops tagged with that mechanism:
•
Front-end tagging — This mechanism pertains to the tagging of μops that encountered front-end events (for
example, trace cache and instruction counts) and are counted with the Front_end_event event
•
Execution tagging — This mechanism pertains to the tagging of μops that encountered execution events (for
example, instruction types) and are counted with the Execution_Event event.
•
Replay tagging — This mechanism pertains to tagging of μops whose retirement is replayed (for example, a
cache miss) and are counted with the Replay_event event. Branch mispredictions are also tagged with this
mechanism.
•
No tags — This mechanism does not use tags. It uses the Instr_retired and the Uops_ retired events.
Each tagging mechanism is independent from all others; that is, a μop that has been tagged using one mechanism
will not be detected with another mechanism’s tagged-μop detector. For example, if μops are tagged using the
front-end tagging mechanisms, the Replay_event will not count those as tagged μops unless they are also tagged
using the replay tagging mechanism. However, execution tags allow up to four different types of μops to be counted
at retirement through execution tagging.
The independence of tagging mechanisms does not hold when using PEBS. When using PEBS, only one tagging
mechanism should be used at a time.
Certain kinds of μops that cannot be tagged, including I/O, uncacheable and locked accesses, returns, and far
transfers.
Table 19-29 lists the performance monitoring events that support at-retirement counting: specifically the
Front_end_event, Execution_event, Replay_event, Inst_retired and Uops_retired events. The following sections
describe the tagging mechanisms for using these events to tag μop and count tagged μops.
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18.14.6.2 Tagging Mechanism for Front_end_event
The Front_end_event counts μops that have been tagged as encountering any of the following events:
•
μop decode events — Tagging μops for μop decode events requires specifying bits in the ESCR associated with
the performance-monitoring event, Uop_type.
•
Trace cache events — Tagging μops for trace cache events may require specifying certain bits in the
MSR_TC_PRECISE_EVENT MSR (see Table 19-31).
Table 19-29 describes the Front_end_event and Table 19-31 describes metrics that are used to set up a
Front_end_event count.
The MSRs specified in the Table 19-29 that are supported by the front-end tagging mechanism must be set and one
or both of the NBOGUS and BOGUS bits in the Front_end_event event mask must be set to count events. None of
the events currently supported requires the use of the MSR_TC_PRECISE_EVENT MSR.
18.14.6.3 Tagging Mechanism For Execution_event
Table 19-29 describes the Execution_event and Table 19-32 describes metrics that are used to set up an
Execution_event count.
The execution tagging mechanism differs from other tagging mechanisms in how it causes tagging. One upstream
ESCR is used to specify an event to detect and to specify a tag value (bits 5 through 8) to identify that event. A
second downstream ESCR is used to detect μops that have been tagged with that tag value identifier using
Execution_event for the event selection.
The upstream ESCR that counts the event must have its tag enable flag (bit 4) set and must have an appropriate
tag value mask entered in its tag value field. The 4-bit tag value mask specifies which of tag bits should be set for
a particular μop. The value selected for the tag value should coincide with the event mask selected in the downstream ESCR. For example, if a tag value of 1 is set, then the event mask of NBOGUS0 should be enabled, correspondingly in the downstream ESCR. The downstream ESCR detects and counts tagged μops. The normal (not tag
value) mask bits in the downstream ESCR specify which tag bits to count. If any one of the tag bits selected by the
mask is set, the related counter is incremented by one. This mechanism is summarized in the Table 19-32 metrics
that are supported by the execution tagging mechanism. The tag enable and tag value bits are irrelevant for the
downstream ESCR used to select the Execution_event.
The four separate tag bits allow the user to simultaneously but distinctly count up to four execution events at
retirement. (This applies for interrupt-based event sampling. There are additional restrictions for PEBS as noted in
Section 18.14.7.3, “Setting Up the PEBS Buffer.”) It is also possible to detect or count combinations of events by
setting multiple tag value bits in the upstream ESCR or multiple mask bits in the downstream ESCR. For example,
use a tag value of 3H in the upstream ESCR and use NBOGUS0/NBOGUS1 in the downstream ESCR event mask.
18.14.6.4 Tagging Mechanism for Replay_event
Table 19-29 describes the Replay_event and Table 19-33 describes metrics that are used to set up an Replay_event
count.
The replay mechanism enables tagging of μops for a subset of all replays before retirement. Use of the replay
mechanism requires selecting the type of μop that may experience the replay in the MSR_PEBS_MATRIX_VERT
MSR and selecting the type of event in the MSR_PEBS_ENABLE MSR. Replay tagging must also be enabled with the
UOP_Tag flag (bit 24) in the MSR_PEBS_ENABLE MSR.
The Table 19-33 lists the metrics that are support the replay tagging mechanism and the at-retirement events that
use the replay tagging mechanism, and specifies how the appropriate MSRs need to be configured. The replay tags
defined in Table A-5 also enable Processor Event-Based Sampling (PEBS, see Section 17.4.9). Each of these replay
tags can also be used in normal sampling by not setting Bit 24 nor Bit 25 in IA_32_PEBS_ENABLE_MSR. Each of
these metrics requires that the Replay_Event (see Table 19-29) be used to count the tagged μops.
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PERFORMANCE MONITORING
18.14.7 Processor Event-Based Sampling (PEBS)
The debug store (DS) mechanism in processors based on Intel NetBurst microarchitecture allow two types of information to be collected for use in debugging and tuning programs: PEBS records and BTS records. See Section
17.4.5, “Branch Trace Store (BTS),” for a description of the BTS mechanism.
PEBS permits the saving of precise architectural information associated with one or more performance events in
the precise event records buffer, which is part of the DS save area (see Section 17.4.9, “BTS and DS Save Area”).
To use this mechanism, a counter is configured to overflow after it has counted a preset number of events. After
the counter overflows, the processor copies the current state of the general-purpose and EFLAGS registers and
instruction pointer into a record in the precise event records buffer. The processor then resets the count in the
performance counter and restarts the counter. When the precise event records buffer is nearly full, an interrupt is
generated, allowing the precise event records to be saved. A circular buffer is not supported for precise event
records.
PEBS is supported only for a subset of the at-retirement events: Execution_event, Front_end_event, and
Replay_event. Also, PEBS can only be carried out using the one performance counter, the MSR_IQ_COUNTER4
MSR.
In processors based on Intel Core microarchitecture, a similar PEBS mechanism is also supported using
IA32_PMC0 and IA32_PERFEVTSEL0 MSRs (See Section 18.4.4).
18.14.7.1 Detection of the Availability of the PEBS Facilities
The DS feature flag (bit 21) returned by the CPUID instruction indicates (when set) the availability of the DS mechanism in the processor, which supports the PEBS (and BTS) facilities. When this bit is set, the following PEBS facilities are available:
•
The PEBS_UNAVAILABLE flag in the IA32_MISC_ENABLE MSR indicates (when clear) the availability of the
PEBS facilities, including the MSR_PEBS_ENABLE MSR.
•
The enable PEBS flag (bit 24) in the MSR_PEBS_ENABLE MSR allows PEBS to be enabled (set) or disabled
(clear).
•
The IA32_DS_AREA MSR can be programmed to point to the DS save area.
18.14.7.2 Setting Up the DS Save Area
Section 17.4.9.2, “Setting Up the DS Save Area,” describes how to set up and enable the DS save area. This procedure is common for PEBS and BTS.
18.14.7.3 Setting Up the PEBS Buffer
Only the MSR_IQ_COUNTER4 performance counter can be used for PEBS. Use the following procedure to set up the
processor and this counter for PEBS:
1. Set up the precise event buffering facilities. Place values in the precise event buffer base, precise event index,
precise event absolute maximum, and precise event interrupt threshold, and precise event counter reset fields
of the DS buffer management area (see Figure 17-5) to set up the precise event records buffer in memory.
2. Enable PEBS. Set the Enable PEBS flag (bit 24) in MSR_PEBS_ENABLE MSR.
3. Set up the MSR_IQ_COUNTER4 performance counter and its associated CCCR and one or more ESCRs for PEBS
as described in Tables 19-29 through 19-33.
18.14.7.4 Writing a PEBS Interrupt Service Routine
The PEBS facilities share the same interrupt vector and interrupt service routine (called the DS ISR) with the nonprecise event-based sampling and BTS facilities. To handle PEBS interrupts, PEBS handler code must be included in
the DS ISR. See Section 17.4.9.5, “Writing the DS Interrupt Service Routine,” for guidelines for writing the DS ISR.
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18.14.7.5 Other DS Mechanism Implications
The DS mechanism is not available in the SMM. It is disabled on transition to the SMM mode. Similarly the DS
mechanism is disabled on the generation of a machine check exception and is cleared on processor RESET and INIT.
The DS mechanism is available in real address mode.
18.14.8 Operating System Implications
The DS mechanism can be used by the operating system as a debugging extension to facilitate failure analysis.
When using this facility, a 25 to 30 times slowdown can be expected due to the effects of the trace store occurring
on every taken branch.
Depending upon intended usage, the instruction pointers that are part of the branch records or the PEBS records
need to have an association with the corresponding process. One solution requires the ability for the DS specific
operating system module to be chained to the context switch. A separate buffer can then be maintained for each
process of interest and the MSR pointing to the configuration area saved and setup appropriately on each context
switch.
If the BTS facility has been enabled, then it must be disabled and state stored on transition of the system to a sleep
state in which processor context is lost. The state must be restored on return from the sleep state.
It is required that an interrupt gate be used for the DS interrupt as opposed to a trap gate to prevent the generation
of an endless interrupt loop.
Pages that contain buffers must have mappings to the same physical address for all processes/logical processors,
such that any change to CR3 will not change DS addresses. If this requirement cannot be satisfied (that is, the
feature is enabled on a per thread/process basis), then the operating system must ensure that the feature is
enabled/disabled appropriately in the context switch code.
18.15
PERFORMANCE MONITORING AND INTEL HYPER-THREADING
TECHNOLOGY IN PROCESSORS BASED ON INTEL NETBURST®
MICROARCHITECTURE
The performance monitoring capability of processors based on Intel NetBurst microarchitecture and supporting
Intel Hyper-Threading Technology is similar to that described in Section 18.14. However, the capability is extended
so that:
•
•
Performance counters can be programmed to select events qualified by logical processor IDs.
Performance monitoring interrupts can be directed to a specific logical processor within the physical processor.
The sections below describe performance counters, event qualification by logical processor ID, and special purpose
bits in ESCRs/CCCRs. They also describe MSR_PEBS_ENABLE, MSR_PEBS_MATRIX_VERT, and
MSR_TC_PRECISE_EVENT.
18.15.1 ESCR MSRs
Figure 18-47 shows the layout of an ESCR MSR in processors supporting Intel Hyper-Threading Technology.
The functions of the flags and fields are as follows:
•
T1_USR flag, bit 0 — When set, events are counted when thread 1 (logical processor 1) is executing at a
current privilege level (CPL) of 1, 2, or 3. These privilege levels are generally used by application code and
unprotected operating system code.
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PERFORMANCE MONITORING
31 30
25 24
Event
Select
5 4 3 2 1 0
9 8
Tag
Value
Event Mask
Tag Enable
T0_OS
T0_USR
T1_OS
T1_USR
Reserved
63
32
Reserved
Figure 18-47. Event Selection Control Register (ESCR) for the Pentium 4 Processor, Intel Xeon Processor and Intel
Xeon Processor MP Supporting Hyper-Threading Technology
•
T1_OS flag, bit 1 — When set, events are counted when thread 1 (logical processor 1) is executing at CPL of
0. This privilege level is generally reserved for protected operating system code. (When both the T1_OS and
T1_USR flags are set, thread 1 events are counted at all privilege levels.)
•
T0_USR flag, bit 2 — When set, events are counted when thread 0 (logical processor 0) is executing at a CPL
of 1, 2, or 3.
•
T0_OS flag, bit 3 — When set, events are counted when thread 0 (logical processor 0) is executing at CPL of
0. (When both the T0_OS and T0_USR flags are set, thread 0 events are counted at all privilege levels.)
•
Tag enable, bit 4 — When set, enables tagging of μops to assist in at-retirement event counting; when clear,
disables tagging. See Section 18.14.6, “At-Retirement Counting.”
•
Tag value field, bits 5 through 8 — Selects a tag value to associate with a μop to assist in at-retirement
event counting.
•
Event mask field, bits 9 through 24 — Selects events to be counted from the event class selected with the
event select field.
•
Event select field, bits 25 through 30) — Selects a class of events to be counted. The events within this
class that are counted are selected with the event mask field.
The T0_OS and T0_USR flags and the T1_OS and T1_USR flags allow event counting and sampling to be specified
for a specific logical processor (0 or 1) within an Intel Xeon processor MP (See also: Section 8.4.5, “Identifying
Logical Processors in an MP System,” in the Intel® 64 and IA-32 Architectures Software Developer’s Manual,
Volume 3A).
Not all performance monitoring events can be detected within an Intel Xeon processor MP on a per logical
processor basis (see Section 18.15.4, “Performance Monitoring Events”). Some sub-events (specified by an event
mask bits) are counted or sampled without regard to which logical processor is associated with the detected event.
18.15.2 CCCR MSRs
Figure 18-48 shows the layout of a CCCR MSR in processors supporting Intel Hyper-Threading Technology. The
functions of the flags and fields are as follows:
•
Enable flag, bit 12 — When set, enables counting; when clear, the counter is disabled. This flag is cleared on
reset
•
ESCR select field, bits 13 through 15 — Identifies the ESCR to be used to select events to be counted with
the counter associated with the CCCR.
•
Active thread field, bits 16 and 17 — Enables counting depending on which logical processors are active
(executing a thread). This field enables filtering of events based on the state (active or inactive) of the logical
processors. The encodings of this field are as follows:
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PERFORMANCE MONITORING
00 — None. Count only when neither logical processor is active.
01 — Single. Count only when one logical processor is active (either 0 or 1).
10 — Both. Count only when both logical processors are active.
11 — Any. Count when either logical processor is active.
A halted logical processor or a logical processor in the “wait for SIPI” state is considered inactive.
•
Compare flag, bit 18 — When set, enables filtering of the event count; when clear, disables filtering. The
filtering method is selected with the threshold, complement, and edge flags.
Reserved
31 30 29
27 26 25 24 23
20 19 18 17 16 15
Threshold
13 12 11
ESCR
Select
0
Reserved
Reserved
Enable
Active Thread
Compare
Complement
Edge
FORCE_OVF
OVF_PMI_T0
OVF_PMI_T1
Cascade
OVF
63
32
Reserved
Figure 18-48. Counter Configuration Control Register (CCCR)
•
Complement flag, bit 19 — Selects how the incoming event count is compared with the threshold value.
When set, event counts that are less than or equal to the threshold value result in a single count being delivered
to the performance counter; when clear, counts greater than the threshold value result in a count being
delivered to the performance counter (see Section 18.14.5.2, “Filtering Events”). The compare flag is not active
unless the compare flag is set.
•
Threshold field, bits 20 through 23 — Selects the threshold value to be used for comparisons. The
processor examines this field only when the compare flag is set, and uses the complement flag setting to
determine the type of threshold comparison to be made. The useful range of values that can be entered in this
field depend on the type of event being counted (see Section 18.14.5.2, “Filtering Events”).
•
Edge flag, bit 24 — When set, enables rising edge (false-to-true) edge detection of the threshold comparison
output for filtering event counts; when clear, rising edge detection is disabled. This flag is active only when the
compare flag is set.
•
FORCE_OVF flag, bit 25 — When set, forces a counter overflow on every counter increment; when clear,
overflow only occurs when the counter actually overflows.
•
OVF_PMI_T0 flag, bit 26 — When set, causes a performance monitor interrupt (PMI) to be sent to logical
processor 0 when the counter overflows occurs; when clear, disables PMI generation for logical processor 0.
Note that the PMI is generate on the next event count after the counter has overflowed.
•
OVF_PMI_T1 flag, bit 27 — When set, causes a performance monitor interrupt (PMI) to be sent to logical
processor 1 when the counter overflows occurs; when clear, disables PMI generation for logical processor 1.
Note that the PMI is generate on the next event count after the counter has overflowed.
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PERFORMANCE MONITORING
•
Cascade flag, bit 30 — When set, enables counting on one counter of a counter pair when its alternate
counter in the other the counter pair in the same counter group overflows (see Section 18.14.2, “Performance
Counters,” for further details); when clear, disables cascading of counters.
•
OVF flag, bit 31 — Indicates that the counter has overflowed when set. This flag is a sticky flag that must be
explicitly cleared by software.
18.15.3 IA32_PEBS_ENABLE MSR
In a processor supporting Intel Hyper-Threading Technology and based on the Intel NetBurst microarchitecture,
PEBS is enabled and qualified with two bits in the MSR_PEBS_ENABLE MSR: bit 25 (ENABLE_PEBS_MY_THR) and
26 (ENABLE_PEBS_OTH_THR) respectively. These bits do not explicitly identify a specific logical processor by logic
processor ID(T0 or T1); instead, they allow a software agent to enable PEBS for subsequent threads of execution
on the same logical processor on which the agent is running (“my thread”) or for the other logical processor in the
physical package on which the agent is not running (“other thread”).
PEBS is supported for only a subset of the at-retirement events: Execution_event, Front_end_event, and
Replay_event. Also, PEBS can be carried out only with two performance counters: MSR_IQ_CCCR4 (MSR address
370H) for logical processor 0 and MSR_IQ_CCCR5 (MSR address 371H) for logical processor 1.
Performance monitoring tools should use a processor affinity mask to bind the kernel mode components that need
to modify the ENABLE_PEBS_MY_THR and ENABLE_PEBS_OTH_THR bits in the MSR_PEBS_ENABLE MSR to a
specific logical processor. This is to prevent these kernel mode components from migrating between different
logical processors due to OS scheduling.
18.15.4 Performance Monitoring Events
All of the events listed in Table 19-28 and 19-29 are available in an Intel Xeon processor MP. When Intel HyperThreading Technology is active, many performance monitoring events can be can be qualified by the logical
processor ID, which corresponds to bit 0 of the initial APIC ID. This allows for counting an event in any or all of the
logical processors. However, not all the events have this logic processor specificity, or thread specificity.
Here, each event falls into one of two categories:
•
•
Thread specific (TS) — The event can be qualified as occurring on a specific logical processor.
Thread independent (TI) — The event cannot be qualified as being associated with a specific logical
processor.
Table 19-34 gives logical processor specific information (TS or TI) for each of the events described in Tables 19-28
and 19-29. If for example, a TS event occurred in logical processor T0, the counting of the event (as shown in Table
18-66) depends only on the setting of the T0_USR and T0_OS flags in the ESCR being used to set up the event
counter. The T1_USR and T1_OS flags have no effect on the count.
Table 18-66. Effect of Logical Processor and CPL Qualification
for Logical-Processor-Specific (TS) Events
T1_OS/T1_USR = 00
T1_OS/T1_USR = 01
T1_OS/T1_USR = 11
T1_OS/T1_USR = 10
T0_OS/T0_USR = 00
Zero count
Counts while T1 in USR
Counts while T1 in OS or
USR
Counts while T1 in OS
T0_OS/T0_USR = 01
Counts while T0 in USR
Counts while T0 in USR
or T1 in USR
Counts while (a) T0 in
USR or (b) T1 in OS or (c)
T1 in USR
Counts while (a) T0 in OS
or (b) T1 in OS
T0_OS/T0_USR = 11
Counts while T0 in OS or
USR
Counts while (a) T0 in OS
or (b) T0 in USR or (c) T1
in USR
Counts irrespective of
CPL, T0, T1
Counts while (a) T0 in OS
or (b) or T0 in USR or (c)
T1 in OS
T0_OS/T0_USR = 10
Counts T0 in OS
Counts T0 in OS or T1 in
USR
Counts while (a)T0 in Os
or (b) T1 in OS or (c) T1
in USR
Counts while (a) T0 in OS
or (b) T1 in OS
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PERFORMANCE MONITORING
When a bit in the event mask field is TI, the effect of specifying bit-0-3 of the associated ESCR are described in
Table 15-6. For events that are marked as TI in Chapter 19, the effect of selectively specifying T0_USR, T0_OS,
T1_USR, T1_OS bits is shown in Table 18-67.
Table 18-67. Effect of Logical Processor and CPL Qualification
for Non-logical-Processor-specific (TI) Events
T1_OS/T1_USR = 00
T1_OS/T1_USR = 01
T1_OS/T1_USR = 11
T1_OS/T1_USR = 10
T0_OS/T0_USR = 00
Zero count
Counts while (a) T0 in
USR or (b) T1 in USR
Counts irrespective of
CPL, T0, T1
Counts while (a) T0 in OS
or (b) T1 in OS
T0_OS/T0_USR = 01
Counts while (a) T0 in
USR or (b) T1 in USR
Counts while (a) T0 in
USR or (b) T1 in USR
Counts irrespective of
CPL, T0, T1
Counts irrespective of
CPL, T0, T1
T0_OS/T0_USR = 11
Counts irrespective of
CPL, T0, T1
Counts irrespective of
CPL, T0, T1
Counts irrespective of
CPL, T0, T1
Counts irrespective of
CPL, T0, T1
T0_OS/T0_USR = 0
Counts while (a) T0 in OS
or (b) T1 in OS
Counts irrespective of
CPL, T0, T1
Counts irrespective of
CPL, T0, T1
Counts while (a) T0 in OS
or (b) T1 in OS
18.16
COUNTING CLOCKS
The count of cycles, also known as clockticks, forms a the basis for measuring how long a program takes to
execute. Clockticks are also used as part of efficiency ratios like cycles per instruction (CPI). Processor clocks may
stop ticking under circumstances like the following:
•
The processor is halted when there is nothing for the CPU to do. For example, the processor may halt to save
power while the computer is servicing an I/O request. When Intel Hyper-Threading Technology is enabled, both
logical processors must be halted for performance-monitoring counters to be powered down.
•
The processor is asleep as a result of being halted or because of a power-management scheme. There are
different levels of sleep. In the some deep sleep levels, the time-stamp counter stops counting.
In addition, processor core clocks may undergo transitions at different ratios relative to the processor’s bus clock
frequency. Some of the situations that can cause processor core clock to undergo frequency transitions include:
•
•
TM2 transitions
Enhanced Intel SpeedStep Technology transitions (P-state transitions)
For Intel processors that support Intel Dynamic Acceleration or XE operation, the processor core clocks may
operate at a frequency that differs from the Processor Base frequency (as indicated by processor frequency information reported by CPUID instruction). See Section 18.16.5 for more detail.
There are several ways to count processor clock cycles to monitor performance. These are:
•
Non-halted clockticks — Measures clock cycles in which the specified logical processor is not halted and is
not in any power-saving state. When Intel Hyper-Threading Technology is enabled, ticks can be measured on a
per-logical-processor basis. There are also performance events on dual-core processors that measure
clockticks per logical processor when the processor is not halted.
•
Non-sleep clockticks — Measures clock cycles in which the specified physical processor is not in a sleep mode
or in a power-saving state. These ticks cannot be measured on a logical-processor basis.
•
Time-stamp counter — Measures clock cycles in which the physical processor is not in deep sleep. These ticks
cannot be measured on a logical-processor basis.
•
Reference clockticks — TM2 or Enhanced Intel SpeedStep technology are two examples of processor
features that can cause processor core clockticks to represent non-uniform tick intervals due to change of bus
ratios. Performance events that counts clockticks of a constant reference frequency was introduced Intel Core
Duo and Intel Core Solo processors. The mechanism is further enhanced on processors based on Intel Core
microarchitecture.
Some processor models permit clock cycles to be measured when the physical processor is not in deep sleep (by
using the time-stamp counter and the RDTSC instruction). Note that such ticks cannot be measured on a perlogical-processor basis. See Section 17.15, “Time-Stamp Counter,” for detail on processor capabilities.
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PERFORMANCE MONITORING
The first two methods use performance counters and can be set up to cause an interrupt upon overflow (for
sampling). They may also be useful where it is easier for a tool to read a performance counter than to use a time
stamp counter (the timestamp counter is accessed using the RDTSC instruction).
For applications with a significant amount of I/O, there are two ratios of interest:
•
Non-halted CPI — Non-halted clockticks/instructions retired measures the CPI for phases where the CPU was
being used. This ratio can be measured on a logical-processor basis when Intel Hyper-Threading Technology is
enabled.
•
Nominal CPI — Time-stamp counter ticks/instructions retired measures the CPI over the duration of a
program, including those periods when the machine halts while waiting for I/O.
18.16.1 Non-Halted Clockticks
Use the following procedure to program ESCRs and CCCRs to obtain non-halted clockticks on processors based on
Intel NetBurst microarchitecture:
1. Select an ESCR for the global_power_events and specify the RUNNING sub-event mask and the desired
T0_OS/T0_USR/T1_OS/T1_USR bits for the targeted processor.
2. Select an appropriate counter.
3. Enable counting in the CCCR for that counter by setting the enable bit.
18.16.2 Non-Sleep Clockticks
Performance monitoring counters can be configured to count clockticks whenever the performance monitoring
hardware is not powered-down. To count Non-sleep Clockticks with a performance-monitoring counter, do the
following:
1. Select one of the 18 counters.
2. Select any of the ESCRs whose events the selected counter can count. Set its event select to anything other
than no_event. This may not seem necessary, but the counter may be disabled if this is not done.
3. Turn threshold comparison on in the CCCR by setting the compare bit to 1.
4. Set the threshold to 15 and the complement to 1 in the CCCR. Since no event can exceed this threshold, the
threshold condition is met every cycle and the counter counts every cycle. Note that this overrides any qualification (e.g. by CPL) specified in the ESCR.
5. Enable counting in the CCCR for the counter by setting the enable bit.
In most cases, the counts produced by the non-halted and non-sleep metrics are equivalent if the physical package
supports one logical processor and is not placed in a power-saving state. Operating systems may execute an HLT
instruction and place a physical processor in a power-saving state.
On processors that support Intel Hyper-Threading Technology (Intel HT Technology), each physical package can
support two or more logical processors. Current implementation of Intel HT Technology provides two logical
processors for each physical processor. While both logical processors can execute two threads simultaneously, one
logical processor may halt to allow the other logical processor to execute without sharing execution resources
between two logical processors.
Non-halted Clockticks can be set up to count the number of processor clock cycles for each logical processor whenever the logical processor is not halted (the count may include some portion of the clock cycles for that logical
processor to complete a transition to a halted state). Physical processors that support Intel HT Technology enter
into a power-saving state if all logical processors halt.
The Non-sleep Clockticks mechanism uses a filtering mechanism in CCCRs. The mechanism will continue to increment as long as one logical processor is not halted or in a power-saving state. Applications may cause a processor
to enter into a power-saving state by using an OS service that transfers control to an OS’s idle loop. The idle loop
then may place the processor into a power-saving state after an implementation-dependent period if there is no
work for the processor.
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PERFORMANCE MONITORING
18.16.3 Incrementing the Time-Stamp Counter
The time-stamp counter increments when the clock signal on the system bus is active and when the sleep pin is not
asserted. The counter value can be read with the RDTSC instruction.
The time-stamp counter and the non-sleep clockticks count may not agree in all cases and for all processors. See
Section 17.15, “Time-Stamp Counter,” for more information on counter operation.
18.16.4 Non-Halted Reference Clockticks
Software can use either processor-specific performance monitor events (for example: CPU_CLK_UNHALTED.BUS
on processors based on the Intel Core microarchitecture, and equivalent event specifications on the Intel Core Duo
and Intel Core Solo processors) to count non-halted reference clockticks.
These events count reference clock cycles whenever the specified processor is not halted. The counter counts reference cycles associated with a fixed-frequency clock source irrespective of P-state, TM2, or frequency transitions
that may occur to the processor.
18.16.5 Cycle Counting and Opportunistic Processor Operation
As a result of the state transitions due to opportunistic processor performance operation (see Chapter 14, “Power
and Thermal Management”), a logical processor or a processor core can operate at frequency different from the
Processor Base frequency.
The following items are expected to hold true irrespective of when opportunistic processor operation causes state
transitions:
•
•
The time stamp counter operates at a fixed-rate frequency of the processor.
•
The IA32_FIXED_CTR2 counter increments at the same TSC frequency irrespective of any transitions caused by
opportunistic processor operation.
•
•
The Local APIC timer operation is unaffected by opportunistic processor operation.
The IA32_MPERF counter increments at a fixed frequency irrespective of any transitions caused by opportunistic processor operation.
The TSC, IA32_MPERF, and IA32_FIXED_CTR2 operate at close to the maximum non-turbo frequency, which is
equal to the product of scalable bus frequency and maximum non-turbo ratio.
For processors based on Intel Core microarchitecture, the scalable bus frequency is encoded in the bit field
MSR_FSB_FREQ[2:0] at (0CDH), see Chapter 35, “Model-Specific Registers (MSRs)”. The maximum resolved bus
ratio can be read from the following bit field:
•
If XE operation is disabled, the maximum resolved bus ratio can be read in MSR_PLATFORM_ID[12:8]. It
corresponds to the Processor Base frequency.
•
IF XE operation is enabled, the maximum resolved bus ratio is given in MSR_PERF_STAT[44:40], it corresponds
to the maximum XE operation frequency configured by BIOS.
XE operation of an Intel 64 processor is implementation specific. XE operation can be enabled only by BIOS. If
MSR_PERF_STAT[31] is set, XE operation is enabled. The MSR_PERF_STAT[31] field is read-only.
18.17
IA32_PERF_CAPABILITIES MSR ENUMERATION
The layout of IA32_PERF_CAPABILITIES MSR is shown in Figure 18-49, it provides enumeration of a variety of
interfaces:
•
IA32_PERF_CAPABILITIES.LBR_FMT[bits 5:0]: encodes the LBR format, details are described in Section
17.4.8.1.
•
IA32_PERF_CAPABILITIES.PEBSTrap[6]: Trap/Fault-like indicator of PEBS recording assist, see Section
18.4.4.2.
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PERFORMANCE MONITORING
•
IA32_PERF_CAPABILITIES.PEBSArchRegs[7]: Indicator of PEBS assist save architectural registers, see Section
18.4.4.2.
•
IA32_PERF_CAPABILITIES.PEBS_FMT[bits 11:8]: Specifies the encoding of the layout of PEBS records, see
Section 18.4.4.2.
•
IA32_PERF_CAPABILITIES.SMM_FRZ[12]: Indicates IA32_DEBUGCTL.FREEZE_WHILE_SMM is supported if 1,
see Section 18.17.1.
•
IA32_PERF_CAPABILITIES.FULL_WRITE[13]: Indicates the processor supports IA32_A_PMCx interface for
updating bits 32 and above of IA32_PMCx, see Section 18.2.5.
63
13 12 11
8 7 6 5 43 2 1 0
FW_WRITE (R/O)
SMM_FREEZE (R/O)
PEBS_REC_FMT (R/O)
PEBS_ARCH_REG (R/O)
PEBS_TRAP (R/O)
LBR_FMT (R/O)
Reserved
Figure 18-49. Layout of IA32_PERF_CAPABILITIES MSR
18.17.1
Filtering of SMM Handler Overhead
When performance monitoring facilities and/or branch profiling facilities (see Section 17.5, “Last Branch, Interrupt,
and Exception Recording (Intel® Core™ 2 Duo and Intel® Atom™ Processors)”) are enabled, these facilities
capture event counts, branch records and branch trace messages occurring in a logical processor. The occurrence
of interrupts, instruction streams due to various interrupt handlers all contribute to the results recorded by these
facilities.
If CPUID.01H:ECX.PDCM[bit 15] is 1, the processor supports the IA32_PERF_CAPABILITIES MSR. If
IA32_PERF_CAPABILITIES.FREEZE_WHILE_SMM[Bit 12] is 1, the processor supports the ability for system software using performance monitoring and/or branch profiling facilities to filter out the effects of servicing system
management interrupts.
If the FREEZE_WHILE_SMM capability is enabled on a logical processor and after an SMI is delivered, the processor
will clear all the enable bits of IA32_PERF_GLOBAL_CTRL, save a copy of the content of IA32_DEBUGCTL and
disable LBR, BTF, TR, and BTS fields of IA32_DEBUGCTL before transferring control to the SMI handler.
The enable bits of IA32_PERF_GLOBAL_CTRL will be set to 1, the saved copy of IA32_DEBUGCTL prior to SMI
delivery will be restored , after the SMI handler issues RSM to complete its servicing.
It is the responsibility of the SMM code to ensure the state of the performance monitoring and branch profiling facilities are preserved upon entry or until prior to exiting the SMM. If any of this state is modified due to actions by the
SMM code, the SMM code is required to restore such state to the values present at entry to the SMM handler.
System software is allowed to set IA32_DEBUGCTL.FREEZE_WHILE_SMM_EN[bit 14] to 1 only supported as indicated by IA32_PERF_CAPABILITIES.FREEZE_WHILE_SMM[Bit 12] reporting 1.
18.18
PERFORMANCE MONITORING AND DUAL-CORE TECHNOLOGY
The performance monitoring capability of dual-core processors duplicates the microarchitectural resources of a
single-core processor implementation. Each processor core has dedicated performance monitoring resources.
In the case of Pentium D processor, each logical processor is associated with dedicated resources for performance
monitoring. In the case of Pentium processor Extreme edition, each processor core has dedicated resources, but
Vol. 3B 18-105
PERFORMANCE MONITORING
two logical processors in the same core share performance monitoring resources (see Section 18.15, “Performance
Monitoring and Intel Hyper-Threading Technology in Processors Based on Intel NetBurst® Microarchitecture”).
18.19
PERFORMANCE MONITORING ON 64-BIT INTEL XEON PROCESSOR MP
WITH UP TO 8-MBYTE L3 CACHE
The 64-bit Intel Xeon processor MP with up to 8-MByte L3 cache has a CPUID signature of family [0FH], model [03H
or 04H]. Performance monitoring capabilities available to Pentium 4 and Intel Xeon processors with the same
values (see Section 18.1 and Section 18.15) apply to the 64-bit Intel Xeon processor MP with an L3 cache.
The level 3 cache is connected between the system bus and IOQ through additional control logic. See Figure 18-50.
System Bus
iBUSQ and iSNPQ
3rd Level Cache
8 or 4 -way
iFSB
IOQ
Processor Core
(Front end, Execution,
Retirement, L1, L2
Figure 18-50. Block Diagram of 64-bit Intel Xeon Processor MP with 8-MByte L3
Additional performance monitoring capabilities and facilities unique to 64-bit Intel Xeon processor MP with an L3
cache are described in this section. The facility for monitoring events consists of a set of dedicated model-specific
registers (MSRs), each dedicated to a specific event. Programming of these MSRs requires using RDMSR/WRMSR
instructions with 64-bit values.
The lower 32-bits of the MSRs at addresses 107CC through 107D3 are treated as 32 bit performance counter registers. These performance counters can be accessed using RDPMC instruction with the index starting from 18
through 25. The EDX register returns zero when reading these 8 PMCs.
The performance monitoring capabilities consist of four events. These are:
•
IBUSQ event — This event detects the occurrence of micro-architectural conditions related to the iBUSQ unit.
It provides two MSRs: MSR_IFSB_IBUSQ0 and MSR_IFSB_IBUSQ1. Configure sub-event qualification and
enable/disable functions using the high 32 bits of these MSRs. The low 32 bits act as a 32-bit event counter.
Counting starts after software writes a non-zero value to one or more of the upper 32 bits. See Figure 18-51.
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PERFORMANCE MONITORING
MSR_IFSB_IBUSQx, Addresses: 107CCH and 107CDH
63
49 48
60 59 58 57 56 55
0
38 37 36 35 34 33 32 31
46 45
1 1
Saturate
Fill_match
Eviction_match
L3_state_match
Snoop_match
Type_match
T1_match
T0_match
32 bit event count
Reserved
Figure 18-51. MSR_IFSB_IBUSQx, Addresses: 107CCH and 107CDH
•
ISNPQ event — This event detects the occurrence of microarchitectural conditions related to the iSNPQ unit.
It provides two MSRs: MSR_IFSB_ISNPQ0 and MSR_IFSB_ISNPQ1. Configure sub-event qualifications and
enable/disable functions using the high 32 bits of the MSRs. The low 32-bits act as a 32-bit event counter.
Counting starts after software writes a non-zero value to one or more of the upper 32-bits. See Figure 18-52.
MSR_IFSB_ISNPQx, Addresses: 107CEH and 107CFH
63
60 59 58 57 56 55
48
46 45
Reserved
39 38 37 36 35 34 33 32
Saturate
L3_state_match
Snoop_match
Type_match
Agent_match
T1_match
T0_match
31
0
32 bit event count
Figure 18-52. MSR_IFSB_ISNPQx, Addresses: 107CEH and 107CFH
•
EFSB event — This event can detect the occurrence of micro-architectural conditions related to the iFSB unit
or system bus. It provides two MSRs: MSR_EFSB_DRDY0 and MSR_EFSB_DRDY1. Configure sub-event qualifications and enable/disable functions using the high 32 bits of the 64-bit MSR. The low 32-bit act as a 32-bit
event counter. Counting starts after software writes a non-zero value to one or more of the qualification bits in
the upper 32-bits of the MSR. See Figure 18-53.
Vol. 3B 18-107
PERFORMANCE MONITORING
MSR_EFSB_DRDYx, Addresses: 107D0H and 107D1H
63
60 59 58 57 56 55
50 49 48
39 38 37 36 35 34 33 32
Saturate
Other
Own
Reserved
31
0
32 bit event count
Figure 18-53. MSR_EFSB_DRDYx, Addresses: 107D0H and 107D1H
•
IBUSQ Latency event — This event accumulates weighted cycle counts for latency measurement of transactions in the iBUSQ unit. The count is enabled by setting MSR_IFSB_CTRL6[bit 26] to 1; the count freezes after
software sets MSR_IFSB_CTRL6[bit 26] to 0. MSR_IFSB_CNTR7 acts as a 64-bit event counter for this event.
See Figure 18-54.
MSR_IFSB_CTL6 Address: 107D2H
63
59
0
57
Enable
MSR_IFSB_CNTR7 Address: 107D3H
Reserved
0
63
64 bit event count
Figure 18-54. MSR_IFSB_CTL6, Address: 107D2H;
MSR_IFSB_CNTR7, Address: 107D3H
18.20
PERFORMANCE MONITORING ON L3 AND CACHING BUS CONTROLLER
SUB-SYSTEMS
The Intel Xeon processor 7400 series and Dual-Core Intel Xeon processor 7100 series employ a distinct L3/caching
bus controller sub-system. These sub-system have a unique set of performance monitoring capability and
programming interfaces that are largely common between these two processor families.
Intel Xeon processor 7400 series are based on 45 nm enhanced Intel Core microarchitecture. The CPUID signature
is indicated by DisplayFamily_DisplayModel value of 06_1DH (see CPUID instruction in Chapter 3, “Instruction Set
Reference, A-M” in the Intel® 64 and IA-32 Architectures Software Developer’s Manual, Volume 2A). Intel Xeon
processor 7400 series have six processor cores that share an L3 cache.
Dual-Core Intel Xeon processor 7100 series are based on Intel NetBurst microarchitecture, have a CPUID signature
of family [0FH], model [06H] and a unified L3 cache shared between two cores. Each core in an Intel Xeon
processor 7100 series supports Intel Hyper-Threading Technology, providing two logical processors per core.
Both Intel Xeon processor 7400 series and Intel Xeon processor 7100 series support multi-processor configurations
using system bus interfaces. In Intel Xeon processor 7400 series, the L3/caching bus controller sub-system
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PERFORMANCE MONITORING
provides three Simple Direct Interface (SDI) to service transactions originated the XQ-replacement SDI logic in
each dual-core modules. In Intel Xeon processor 7100 series, the IOQ logic in each processor core is replaced with
a Simple Direct Interface (SDI) logic. The L3 cache is connected between the system bus and the SDI through
additional control logic. See Figure 18-55 for the block configuration of six processor cores and the L3/Caching bus
controller sub-system in Intel Xeon processor 7400 series. Figure 18-55 shows the block configuration of two
processor cores (four logical processors) and the L3/Caching bus controller sub-system in Intel Xeon processor
7100 series.
FSB
GBSQ, GSNPQ,
GINTQ, ...
L3
SDI
SDI interface
L2
Core
SDI interface
L2
Core
Core
SDI interface
L2
Core
Core
Core
Figure 18-55. Block Diagram of Intel Xeon Processor 7400 Series
Almost all of the performance monitoring capabilities available to processor cores with the same CPUID signatures
(see Section 18.1 and Section 18.15) apply to Intel Xeon processor 7100 series. The MSRs used by performance
monitoring interface are shared between two logical processors in the same processor core.
The performance monitoring capabilities available to processor with DisplayFamily_DisplayModel signature
06_17H also apply to Intel Xeon processor 7400 series. Each processor core provides its own set of MSRs for
performance monitoring interface.
The IOQ_allocation and IOQ_active_entries events are not supported in Intel Xeon processor 7100 series and 7400
series. Additional performance monitoring capabilities applicable to the L3/caching bus controller sub-system are
described in this section.
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PERFORMANCE MONITORING
FSB
GBSQ, GSNPQ,
GINTQ, ...
L3
SDI
SDI interface
SDI interface
Processor core
Processor core
Logical
processor
Logical
processor
Logical
processor
Logical
processor
Figure 18-56. Block Diagram of Intel Xeon Processor 7100 Series
18.20.1 Overview of Performance Monitoring with L3/Caching Bus Controller
The facility for monitoring events consists of a set of dedicated model-specific registers (MSRs). There are eight
event select/counting MSRs that are dedicated to counting events associated with specified microarchitectural
conditions. Programming of these MSRs requires using RDMSR/WRMSR instructions with 64-bit values. In addition,
an MSR MSR_EMON_L3_GL_CTL provides simplified interface to control freezing, resetting, re-enabling operation
of any combination of these event select/counting MSRs.
The eight MSRs dedicated to count occurrences of specific conditions are further divided to count three sub-classes
of microarchitectural conditions:
•
Two MSRs (MSR_EMON_L3_CTR_CTL0 and MSR_EMON_L3_CTR_CTL1) are dedicated to counting GBSQ
events. Up to two GBSQ events can be programmed and counted simultaneously.
•
Two MSRs (MSR_EMON_L3_CTR_CTL2 and MSR_EMON_L3_CTR_CTL3) are dedicated to counting GSNPQ
events. Up to two GBSQ events can be programmed and counted simultaneously.
•
Four MSRs (MSR_EMON_L3_CTR_CTL4, MSR_EMON_L3_CTR_CTL5, MSR_EMON_L3_CTR_CTL6, and
MSR_EMON_L3_CTR_CTL7) are dedicated to counting external bus operations.
The bit fields in each of eight MSRs share the following common characteristics:
•
Bits 63:32 is the event control field that includes an event mask and other bit fields that control counter
operation. The event mask field specifies details of the microarchitectural condition, and its definition differs
across GBSQ, GSNPQ, FSB.
•
Bits 31:0 is the event count field. If the specified condition is met during each relevant clock domain of the
event logic, the matched condition signals the counter logic to increment the associated event count field. The
lower 32-bits of these 8 MSRs at addresses 107CC through 107D3 are treated as 32 bit performance counter
registers.
In Dual-Core Intel Xeon processor 7100 series, the uncore performance counters can be accessed using RDPMC
instruction with the index starting from 18 through 25. The EDX register returns zero when reading these 8 PMCs.
In Intel Xeon processor 7400 series, RDPMC with ECX between 2 and 9 can be used to access the eight uncore
performance counter/control registers.
18-110 Vol. 3B
PERFORMANCE MONITORING
18.20.2 GBSQ Event Interface
The layout of MSR_EMON_L3_CTR_CTL0 and MSR_EMON_L3_CTR_CTL1 is given in Figure 18-57. Counting starts
after software writes a non-zero value to one or more of the upper 32 bits.
The event mask field (bits 58:32) consists of the following eight attributes:
•
Agent_Select (bits 35:32): The definition of this field differs slightly between Intel Xeon processor 7100 and
7400.
For Intel Xeon processor 7100 series, each bit specifies a logical processor in the physical package. The lower
two bits corresponds to two logical processors in the first processor core, the upper two bits corresponds to two
logical processors in the second processor core. 0FH encoding matches transactions from any logical processor.
For Intel Xeon processor 7400 series, each bit of [34:32] specifies the SDI logic of a dual-core module as the
originator of the transaction. A value of 0111B in bits [35:32] specifies transaction from any processor core.
MSR_EMON_L3_CTR_CTL0/1, Addresses: 107CCH/107CDH
63
60 59 58 57 56 55 54 53
47 46
44 43
Reserved
38 37 36 35
32
Saturate
Cross_snoop
Fill_eviction
Core_module_select
L3_state
Snoop_match
Type_match
Data_flow
Agent_select
31
0
32 bit event count
Figure 18-57. MSR_EMON_L3_CTR_CTL0/1, Addresses: 107CCH/107CDH
•
•
Data_Flow (bits 37:36): Bit 36 specifies demand transactions, bit 37 specifies prefetch transactions.
•
Snoop_Match: (bits 46:44): The three bits specify (in ascending bit position) clean snoop result, HIT snoop
result, and HITM snoop results respectively.
•
•
L3_State (bits 53:47): Each bit specifies an L2 coherency state.
Type_Match (bits 43:38): Specifies transaction types. If all six bits are set, event count will include all
transaction types.
Core_Module_Select (bits 55:54): The valid encodings for L3 lookup differ slightly between Intel Xeon
processor 7100 and 7400.
For Intel Xeon processor 7100 series,
— 00B: Match transactions from any core in the physical package
— 01B: Match transactions from this core only
— 10B: Match transactions from the other core in the physical package
— 11B: Match transaction from both cores in the physical package
For Intel Xeon processor 7400 series,
— 00B: Match transactions from any dual-core module in the physical package
— 01B: Match transactions from this dual-core module only
— 10B: Match transactions from either one of the other two dual-core modules in the physical package
Vol. 3B 18-111
PERFORMANCE MONITORING
— 11B: Match transaction from more than one dual-core modules in the physical package
•
Fill_Eviction (bits 57:56): The valid encodings are
— 00B: Match any transactions
— 01B: Match transactions that fill L3
— 10B: Match transactions that fill L3 without an eviction
— 11B: Match transaction fill L3 with an eviction
•
Cross_Snoop (bit 58): The encodings are
\
— 0B: Match any transactions
— 1B: Match cross snoop transactions
For each counting clock domain, if all eight attributes match, event logic signals to increment the event count field.
18.20.3 GSNPQ Event Interface
The layout of MSR_EMON_L3_CTR_CTL2 and MSR_EMON_L3_CTR_CTL3 is given in Figure 18-58. Counting starts
after software writes a non-zero value to one or more of the upper 32 bits.
The event mask field (bits 58:32) consists of the following six attributes:
•
Agent_Select (bits 37:32): The definition of this field differs slightly between Intel Xeon processor 7100 and
7400.
•
For Intel Xeon processor 7100 series, each of the lowest 4 bits specifies a logical processor in the physical
package. The lowest two bits corresponds to two logical processors in the first processor core, the next two bits
corresponds to two logical processors in the second processor core. Bit 36 specifies other symmetric agent
transactions. Bit 37 specifies central agent transactions. 3FH encoding matches transactions from any logical
processor.
For Intel Xeon processor 7400 series, each of the lowest 3 bits specifies a dual-core module in the physical
package. Bit 37 specifies central agent transactions.
•
Type_Match (bits 43:38): Specifies transaction types. If all six bits are set, event count will include any
transaction types.
•
Snoop_Match: (bits 46:44): The three bits specify (in ascending bit position) clean snoop result, HIT snoop
result, and HITM snoop results respectively.
•
•
L2_State (bits 53:47): Each bit specifies an L3 coherency state.
Core_Module_Select (bits 56:54): Bit 56 enables Core_Module_Select matching. If bit 56 is clear,
Core_Module_Select encoding is ignored. The valid encodings for the lower two bits (bit 55, 54) differ slightly
between Intel Xeon processor 7100 and 7400.
For Intel Xeon processor 7100 series, if bit 56 is set, the valid encodings for the lower two bits (bit 55, 54) are
— 00B: Match transactions from only one core (irrespective which core) in the physical package
— 01B: Match transactions from this core and not the other core
— 10B: Match transactions from the other core in the physical package, but not this core
— 11B: Match transaction from both cores in the physical package
For Intel Xeon processor 7400 series, if bit 56 is set, the valid encodings for the lower two bits (bit 55, 54) are
— 00B: Match transactions from only one dual-core module (irrespective which module) in the physical
package.
— 01B: Match transactions from one or more dual-core modules.
— 10B: Match transactions from two or more dual-core modules.
— 11B: Match transaction from all three dual-core modules in the physical package.
•
Block_Snoop (bit 57): specifies blocked snoop.
For each counting clock domain, if all six attributes match, event logic signals to increment the event count field.
18-112 Vol. 3B
PERFORMANCE MONITORING
Reserved
MSR_EMON_L3_CTR_CTL2/3, Addresses: 107CEH/107CFH
63
60 59 58 57 56 55 54 53
47 46
44 43
39 38 37 36
32
Saturate
Block_snoop
Core_select
L2_state
Snoop_match
Type_match
Agent_match
31
0
32 bit event count
Figure 18-58. MSR_EMON_L3_CTR_CTL2/3, Addresses: 107CEH/107CFH
18.20.4 FSB Event Interface
The layout of MSR_EMON_L3_CTR_CTL4 through MSR_EMON_L3_CTR_CTL7 is given in Figure 18-59. Counting
starts after software writes a non-zero value to one or more of the upper 32 bits.
The event mask field (bits 58:32) is organized as follows:
•
•
Bit 58: must set to 1.
FSB_Submask (bits 57:32): Specifies FSB-specific sub-event mask.
The FSB sub-event mask defines a set of independent attributes. The event logic signals to increment the associated event count field if one of the attribute matches. Some of the sub-event mask bit counts durations. A duration
event increments at most once per cycle.
MSR_EMON_L3_CTR_CTL4/5/6/7, Addresses: 107D0H-107D3H
63
60 59 58 57 56 55
50 49 48
39 38 37 36 35 34 33 32
1
Reserved
Saturate
FSB submask
31
0
32 bit event count
Figure 18-59. MSR_EMON_L3_CTR_CTL4/5/6/7, Addresses: 107D0H-107D3H
18.20.4.1 FSB Sub-Event Mask Interface
•
•
FSB_type (bit 37:32): Specifies different FSB transaction types originated from this physical package
•
FSB_L_hit (bit 39): Count HIT snoop results from any source for transaction originated from this physical
package
FSB_L_clear (bit 38): Count clean snoop results from any source for transaction originated from this physical
package
Vol. 3B 18-113
PERFORMANCE MONITORING
•
FSB_L_hitm (bit 40): Count HITM snoop results from any source for transaction originated from this physical
package
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
FSB_L_defer (bit 41): Count DEFER responses to this processor’s transactions
FSB_L_retry (bit 42): Count RETRY responses to this processor’s transactions
FSB_L_snoop_stall (bit 43): Count snoop stalls to this processor’s transactions
FSB_DBSY (bit 44): Count DBSY assertions by this processor (without a concurrent DRDY)
FSB_DRDY (bit 45): Count DRDY assertions by this processor
FSB_BNR (bit 46): Count BNR assertions by this processor
FSB_IOQ_empty (bit 47): Counts each bus clocks when the IOQ is empty
FSB_IOQ_full (bit 48): Counts each bus clocks when the IOQ is full
FSB_IOQ_active (bit 49): Counts each bus clocks when there is at least one entry in the IOQ
FSB_WW_data (bit 50): Counts back-to-back write transaction’s data phase.
FSB_WW_issue (bit 51): Counts back-to-back write transaction request pairs issued by this processor.
FSB_WR_issue (bit 52): Counts back-to-back write-read transaction request pairs issued by this processor.
FSB_RW_issue (bit 53): Counts back-to-back read-write transaction request pairs issued by this processor.
FSB_other_DBSY (bit 54): Count DBSY assertions by another agent (without a concurrent DRDY)
FSB_other_DRDY (bit 55): Count DRDY assertions by another agent
FSB_other_snoop_stall (bit 56): Count snoop stalls on the FSB due to another agent
FSB_other_BNR (bit 57): Count BNR assertions from another agent
18.20.5 Common Event Control Interface
The MSR_EMON_L3_GL_CTL MSR provides simplified access to query overflow status of the GBSQ, GSNPQ, FSB
event counters. It also provides control bit fields to freeze, unfreeze, or reset those counters. The following bit
fields are supported:
•
•
•
GL_freeze_cmd (bit 0): Freeze the event counters specified by the GL_event_select field.
•
GL_event_select (bit 23:16): Selects one or more event counters to subject to specified command operations
indicated by bits 2:0. Bit 16 corresponds to MSR_EMON_L3_CTR_CTL0, bit 23 corresponds to
MSR_EMON_L3_CTR_CTL7.
•
GL_event_status (bit 55:48): Indicates the overflow status of each event counters. Bit 48 corresponds to
MSR_EMON_L3_CTR_CTL0, bit 55 corresponds to MSR_EMON_L3_CTR_CTL7.
GL_unfreeze_cmd (bit 1): Unfreeze the event counters specified by the GL_event_select field.
GL_reset_cmd (bit 2): Clear the event count field of the event counters specified by the GL_event_select field.
The event select field is not affected.
In the event control field (bits 63:32) of each MSR, if the saturate control (bit 59, see Figure 18-57 for example) is
set, the event logic forces the value FFFF_FFFFH into the event count field instead of incrementing it.
18.21
PERFORMANCE MONITORING (P6 FAMILY PROCESSOR)
The P6 family processors provide two 40-bit performance counters, allowing two types of events to be monitored
simultaneously. These can either count events or measure duration. When counting events, a counter increments
each time a specified event takes place or a specified number of events takes place. When measuring duration, it
counts the number of processor clocks that occur while a specified condition is true. The counters can count events
or measure durations that occur at any privilege level.
Table 19-37, Chapter 19, lists the events that can be counted with the P6 family performance monitoring counters.
18-114 Vol. 3B
PERFORMANCE MONITORING
NOTE
The performance-monitoring events listed in Chapter 19 are intended to be used as guides for
performance tuning. Counter values reported are not guaranteed to be accurate and should be
used as a relative guide for tuning. Known discrepancies are documented where applicable.
The performance-monitoring counters are supported by four MSRs: the performance event select MSRs
(PerfEvtSel0 and PerfEvtSel1) and the performance counter MSRs (PerfCtr0 and PerfCtr1). These registers can be
read from and written to using the RDMSR and WRMSR instructions, respectively. They can be accessed using
these instructions only when operating at privilege level 0. The PerfCtr0 and PerfCtr1 MSRs can be read from any
privilege level using the RDPMC (read performance-monitoring counters) instruction.
NOTE
The PerfEvtSel0, PerfEvtSel1, PerfCtr0, and PerfCtr1 MSRs and the events listed in Table 19-37 are
model-specific for P6 family processors. They are not guaranteed to be available in other IA-32
processors.
18.21.1 PerfEvtSel0 and PerfEvtSel1 MSRs
The PerfEvtSel0 and PerfEvtSel1 MSRs control the operation of the performance-monitoring counters, with one
register used to set up each counter. They specify the events to be counted, how they should be counted, and the
privilege levels at which counting should take place. Figure 18-60 shows the flags and fields in these MSRs.
The functions of the flags and fields in the PerfEvtSel0 and PerfEvtSel1 MSRs are as follows:
•
Event select field (bits 0 through 7) — Selects the event logic unit to detect certain microarchitectural
conditions (see Table 19-37, for a list of events and their 8-bit codes).
•
Unit mask (UMASK) field (bits 8 through 15) — Further qualifies the event logic unit selected in the event
select field to detect a specific microarchitectural condition. For example, for some cache events, the mask is
used as a MESI-protocol qualifier of cache states (see Table 19-37).
31
24 23 22 21 20 19 18 17 16 15
Counter Mask
(CMASK)
INV—Invert counter mask
EN—Enable counters*
INT—APIC interrupt enable
PC—Pin control
E—Edge detect
OS—Operating system mode
USR—User Mode
I
N E
V N
0
8 7
I
U
N P E O S Unit Mask (UMASK)
S R
T C
Event Select
Reserved
* Only available in PerfEvtSel0.
Figure 18-60. PerfEvtSel0 and PerfEvtSel1 MSRs
•
USR (user mode) flag (bit 16) — Specifies that events are counted only when the processor is operating at
privilege levels 1, 2 or 3. This flag can be used in conjunction with the OS flag.
•
OS (operating system mode) flag (bit 17) — Specifies that events are counted only when the processor is
operating at privilege level 0. This flag can be used in conjunction with the USR flag.
•
E (edge detect) flag (bit 18) — Enables (when set) edge detection of events. The processor counts the
number of deasserted to asserted transitions of any condition that can be expressed by the other fields. The
mechanism is limited in that it does not permit back-to-back assertions to be distinguished. This mechanism
allows software to measure not only the fraction of time spent in a particular state, but also the average length
of time spent in such a state (for example, the time spent waiting for an interrupt to be serviced).
Vol. 3B 18-115
PERFORMANCE MONITORING
•
PC (pin control) flag (bit 19) — When set, the processor toggles the PMi pins and increments the counter
when performance-monitoring events occur; when clear, the processor toggles the PMi pins when the counter
overflows. The toggling of a pin is defined as assertion of the pin for a single bus clock followed by deassertion.
•
INT (APIC interrupt enable) flag (bit 20) — When set, the processor generates an exception through its
local APIC on counter overflow.
•
EN (Enable Counters) Flag (bit 22) — This flag is only present in the PerfEvtSel0 MSR. When set,
performance counting is enabled in both performance-monitoring counters; when clear, both counters are
disabled.
•
INV (invert) flag (bit 23) — When set, inverts the counter-mask (CMASK) comparison, so that both greater
than or equal to and less than comparisons can be made (0: greater than or equal; 1: less than). Note if
counter-mask is programmed to zero, INV flag is ignored.
•
Counter mask (CMASK) field (bits 24 through 31) — When nonzero, the processor compares this mask to
the number of events counted during a single cycle. If the event count is greater than or equal to this mask, the
counter is incremented by one. Otherwise the counter is not incremented. This mask can be used to count
events only if multiple occurrences happen per clock (for example, two or more instructions retired per clock).
If the counter-mask field is 0, then the counter is incremented each cycle by the number of events that
occurred that cycle.
18.21.2 PerfCtr0 and PerfCtr1 MSRs
The performance-counter MSRs (PerfCtr0 and PerfCtr1) contain the event or duration counts for the selected
events being counted. The RDPMC instruction can be used by programs or procedures running at any privilege level
and in virtual-8086 mode to read these counters. The PCE flag in control register CR4 (bit 8) allows the use of this
instruction to be restricted to only programs and procedures running at privilege level 0.
The RDPMC instruction is not serializing or ordered with other instructions. Thus, it does not necessarily wait until
all previous instructions have been executed before reading the counter. Similarly, subsequent instructions may
begin execution before the RDPMC instruction operation is performed.
Only the operating system, executing at privilege level 0, can directly manipulate the performance counters, using
the RDMSR and WRMSR instructions. A secure operating system would clear the PCE flag during system initialization to disable direct user access to the performance-monitoring counters, but provide a user-accessible programming interface that emulates the RDPMC instruction.
The WRMSR instruction cannot arbitrarily write to the performance-monitoring counter MSRs (PerfCtr0 and
PerfCtr1). Instead, the lower-order 32 bits of each MSR may be written with any value, and the high-order 8 bits
are sign-extended according to the value of bit 31. This operation allows writing both positive and negative values
to the performance counters.
18.21.3 Starting and Stopping the Performance-Monitoring Counters
The performance-monitoring counters are started by writing valid setup information in the PerfEvtSel0 and/or
PerfEvtSel1 MSRs and setting the enable counters flag in the PerfEvtSel0 MSR. If the setup is valid, the counters
begin counting following the execution of a WRMSR instruction that sets the enable counter flag. The counters can
be stopped by clearing the enable counters flag or by clearing all the bits in the PerfEvtSel0 and PerfEvtSel1 MSRs.
Counter 1 alone can be stopped by clearing the PerfEvtSel1 MSR.
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PERFORMANCE MONITORING
18.21.4 Event and Time-Stamp Monitoring Software
To use the performance-monitoring counters and time-stamp counter, the operating system needs to provide an
event-monitoring device driver. This driver should include procedures for handling the following operations:
•
•
•
•
•
Feature checking
Initialize and start counters
Stop counters
Read the event counters
Read the time-stamp counter
The event monitor feature determination procedure must check whether the current processor supports the
performance-monitoring counters and time-stamp counter. This procedure compares the family and model of the
processor returned by the CPUID instruction with those of processors known to support performance monitoring.
(The Pentium and P6 family processors support performance counters.) The procedure also checks the MSR and
TSC flags returned to register EDX by the CPUID instruction to determine if the MSRs and the RDTSC instruction
are supported.
The initialize and start counters procedure sets the PerfEvtSel0 and/or PerfEvtSel1 MSRs for the events to be
counted and the method used to count them and initializes the counter MSRs (PerfCtr0 and PerfCtr1) to starting
counts. The stop counters procedure stops the performance counters (see Section 18.21.3, “Starting and Stopping
the Performance-Monitoring Counters”).
The read counters procedure reads the values in the PerfCtr0 and PerfCtr1 MSRs, and a read time-stamp counter
procedure reads the time-stamp counter. These procedures would be provided in lieu of enabling the RDTSC and
RDPMC instructions that allow application code to read the counters.
18.21.5 Monitoring Counter Overflow
The P6 family processors provide the option of generating a local APIC interrupt when a performance-monitoring
counter overflows. This mechanism is enabled by setting the interrupt enable flag in either the PerfEvtSel0 or the
PerfEvtSel1 MSR. The primary use of this option is for statistical performance sampling.
To use this option, the operating system should do the following things on the processor for which performance
events are required to be monitored:
•
•
•
Provide an interrupt vector for handling the counter-overflow interrupt.
•
Provide an event monitor driver that provides the actual interrupt handler and modifies the reserved IDT entry
to point to its interrupt routine.
Initialize the APIC PERF local vector entry to enable handling of performance-monitor counter overflow events.
Provide an entry in the IDT that points to a stub exception handler that returns without executing any instructions.
When interrupted by a counter overflow, the interrupt handler needs to perform the following actions:
•
Save the instruction pointer (EIP register), code-segment selector, TSS segment selector, counter values and
other relevant information at the time of the interrupt.
•
Reset the counter to its initial setting and return from the interrupt.
An event monitor application utility or another application program can read the information collected for analysis
of the performance of the profiled application.
18.22
PERFORMANCE MONITORING (PENTIUM PROCESSORS)
The Pentium processor provides two 40-bit performance counters, which can be used to count events or measure
duration. The counters are supported by three MSRs: the control and event select MSR (CESR) and the performance counter MSRs (CTR0 and CTR1). These can be read from and written to using the RDMSR and WRMSR
instructions, respectively. They can be accessed using these instructions only when operating at privilege level 0.
Vol. 3B 18-117
PERFORMANCE MONITORING
Each counter has an associated external pin (PM0/BP0 and PM1/BP1), which can be used to indicate the state of the
counter to external hardware.
NOTES
The CESR, CTR0, and CTR1 MSRs and the events listed in Table 19-38 are model-specific for the
Pentium processor.
The performance-monitoring events listed in Chapter 19 are intended to be used as guides for
performance tuning. Counter values reported are not guaranteed to be accurate and should be
used as a relative guide for tuning. Known discrepancies are documented where applicable.
18.22.1 Control and Event Select Register (CESR)
The 32-bit control and event select MSR (CESR) controls the operation of performance-monitoring counters CTR0
and CTR1 and the associated pins (see Figure 18-61). To control each counter, the CESR register contains a 6-bit
event select field (ES0 and ES1), a pin control flag (PC0 and PC1), and a 3-bit counter control field (CC0 and CC1).
The functions of these fields are as follows:
•
ES0 and ES1 (event select) fields (bits 0-5, bits 16-21) — Selects (by entering an event code in the field)
up to two events to be monitored. See Table 19-38 for a list of available event codes.
31
26 25 24
P
C
1
22 21
CC1
16 15
ES1
10 9 8
P
C
0
6 5
CC0
0
ESO
PC1—Pin control 1
CC1—Counter control 1
ES1—Event select 1
PC0—Pin control 0
CC0—Counter control 0
ES0—Event select 0
Reserved
Figure 18-61. CESR MSR (Pentium Processor Only)
•
CC0 and CC1 (counter control) fields (bits 6-8, bits 22-24) — Controls the operation of the counter.
Control codes are as follows:
000 — Count nothing (counter disabled)
001 — Count the selected event while CPL is 0, 1, or 2
010 — Count the selected event while CPL is 3
011 — Count the selected event regardless of CPL
100 — Count nothing (counter disabled)
101 — Count clocks (duration) while CPL is 0, 1, or 2
110 — Count clocks (duration) while CPL is 3
111 — Count clocks (duration) regardless of CPL
The highest order bit selects between counting events and counting clocks (duration); the middle bit enables
counting when the CPL is 3; and the low-order bit enables counting when the CPL is 0, 1, or 2.
•
PC0 and PC1 (pin control) flags (bits 9, 25) — Selects the function of the external performance-monitoring
counter pin (PM0/BP0 and PM1/BP1). Setting one of these flags to 1 causes the processor to assert its
associated pin when the counter has overflowed; setting the flag to 0 causes the pin to be asserted when the
counter has been incremented. These flags permit the pins to be individually programmed to indicate the
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PERFORMANCE MONITORING
overflow or incremented condition. The external signalling of the event on the pins will lag the internal event by
a few clocks as the signals are latched and buffered.
While a counter need not be stopped to sample its contents, it must be stopped and cleared or preset before
switching to a new event. It is not possible to set one counter separately. If only one event needs to be changed,
the CESR register must be read, the appropriate bits modified, and all bits must then be written back to CESR. At
reset, all bits in the CESR register are cleared.
18.22.2 Use of the Performance-Monitoring Pins
When performance-monitor pins PM0/BP0 and/or PM1/BP1 are configured to indicate when the performancemonitor counter has incremented and an “occurrence event” is being counted, the associated pin is asserted (high)
each time the event occurs. When a “duration event” is being counted, the associated PM pin is asserted for the
entire duration of the event. When the performance-monitor pins are configured to indicate when the counter has
overflowed, the associated PM pin is asserted when the counter has overflowed.
When the PM0/BP0 and/or PM1/BP1 pins are configured to signal that a counter has incremented, it should be
noted that although the counters may increment by 1 or 2 in a single clock, the pins can only indicate that the
event occurred. Moreover, since the internal clock frequency may be higher than the external clock frequency, a
single external clock may correspond to multiple internal clocks.
A “count up to” function may be provided when the event pin is programmed to signal an overflow of the counter.
Because the counters are 40 bits, a carry out of bit 39 indicates an overflow. A counter may be preset to a specific
value less then 240 − 1. After the counter has been enabled and the prescribed number of events has transpired,
the counter will overflow.
Approximately 5 clocks later, the overflow is indicated externally and appropriate action, such as signaling an interrupt, may then be taken.
The PM0/BP0 and PM1/BP1 pins also serve to indicate breakpoint matches during in-circuit emulation, during which
time the counter increment or overflow function of these pins is not available. After RESET, the PM0/BP0 and
PM1/BP1 pins are configured for performance monitoring, however a hardware debugger may reconfigure these
pins to indicate breakpoint matches.
18.22.3 Events Counted
Events that performance-monitoring counters can be set to count and record (using CTR0 and CTR1) are divided in
two categories: occurrence and duration:
•
Occurrence events — Counts are incremented each time an event takes place. If PM0/BP0 or PM1/BP1 pins
are used to indicate when a counter increments, the pins are asserted each clock counters increment. But if an
event happens twice in one clock, the counter increments by 2 (the pins are asserted only once).
•
Duration events — Counters increment the total number of clocks that the condition is true. When used to
indicate when counters increment, PM0/BP0 and/or PM1/BP1 pins are asserted for the duration.
Vol. 3B 18-119
PERFORMANCE MONITORING
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CHAPTER 19
PERFORMANCE-MONITORING EVENTS
This chapter lists the performance-monitoring events that can be monitored with the Intel 64 or IA-32 processors.
The ability to monitor performance events and the events that can be monitored in these processors are mostly
model-specific, except for architectural performance events, described in Section 19.1.
Non-architectural performance events (i.e. model-specific events) are listed for each generation of microarchitecture:
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Section 19.2 - Processors based on Skylake microarchitecture
Section 19.3 - Processors based on Broadwell microarchitecture
Section 19.4 - Processors based on Haswell microarchitecture
Section 19.4.1 - Processors based on Haswell-E microarchitecture
Section 19.5 - Processors based on Ivy Bridge microarchitecture
Section 19.5.1 - Processors based on Ivy Bridge-E microarchitecture
Section 19.6 - Processors based on Sandy Bridge microarchitecture
Section 19.7 - Processors based on Intel® microarchitecture code name Nehalem
Section 19.8 - Processors based on Intel® microarchitecture code name Westmere
Section 19.9 - Processors based on Enhanced Intel® Core™ microarchitecture
Section 19.10 - Processors based on Intel® Core™ microarchitecture
Section 19.11 - Processors based on the Goldmont microarchitecture
Section 19.12 - Processors based on the Silvermont microarchitecture
Section 19.12.1 - Processors based on the Airmont microarchitecture
Section 19.13 - 45 nm and 32 nm Intel® Atom™ Processors
Section 19.14 - Intel® Core™ Solo and Intel® Core™ Duo processors
Section 19.15 - Processors based on Intel NetBurst® microarchitecture
Section 19.16 - Pentium® M family processors
Section 19.17 - P6 family processors
Section 19.18 - Pentium® processors
NOTE
These performance-monitoring events are intended to be used as guides for performance tuning.
The counter values reported by the performance-monitoring events are approximate and believed
to be useful as relative guides for tuning software. Known discrepancies are documented where
applicable.
All performance event encodings not documented in the appropriate tables for the given processor
are considered reserved, and their use will result in undefined counter updates with associated
overflow actions.
The event tables listed this chapter provide information for tool developers to support architectural
and non-architectural performance monitoring events. The tables are up to date at processor
launch, but are subject to changes. The most up to date event tables and additional details of
performance event implementation for end-user (including additional details beyond event
code/umask) can found at the “perfmon” repository provided by The Intel Open Source Technology
Center (https://download.01.org/perfmon/).
Vol. 3B 19-1
PERFORMANCE-MONITORING EVENTS
19.1
ARCHITECTURAL PERFORMANCE-MONITORING EVENTS
Architectural performance events are introduced in Intel Core Solo and Intel Core Duo processors. They are also
supported on processors based on Intel Core microarchitecture. Table 19-1 lists pre-defined architectural performance events that can be configured using general-purpose performance counters and associated event-select
registers.
Table 19-1. Architectural Performance Events
Event
Num.
Event Mask Mnemonic
Umask
Value
Description
3CH
UnHalted Core Cycles
00H
Unhalted core cycles
3CH
UnHalted Reference Cycles
01H
Unhalted reference cycles
C0H
Instruction Retired
00H
Instruction retired
2EH
LLC Reference
4FH
Longest latency cache references
2EH
LLC Misses
41H
Longest latency cache misses
C4H
Branch Instruction Retired
00H
Branch instruction at retirement
C5H
Branch Misses Retired
00H
Mispredicted Branch Instruction at retirement
Comment
Measures bus
cycle1
NOTES:
1. Implementation of this event in Intel Core 2 processor family, Intel Core Duo, and Intel Core Solo processors measures bus clocks.
Fixed-function performance counters count only events defined in Table 19-2.
Table 19-2. Fixed-Function Performance Counter and Pre-defined Performance Events
Fixed-Function Performance
Counter
Address
Event Mask Mnemonic
Description
IA32_PERF_FIXED_CTR0
309H
Inst_Retired.Any
This event counts the number of instructions that retire
execution. For instructions that consist of multiple microops, this event counts the retirement of the last micro-op
of the instruction. The counter continues counting during
hardware interrupts, traps, and inside interrupt handlers.
IA32_PERF_FIXED_CTR1
30AH
CPU_CLK_UNHALTED.THRE
AD/CPU_CLK_UNHALTED.C
ORE/CPU_CLK_UNHALTED.
THREAD_ANY
The CPU_CLK_UNHALTED.THREAD event counts the
number of core cycles while the logical processor is not in a
halt state.
If there is only one logical processor in a processor core,
CPU_CLK_UNHALTED.CORE counts the unhalted cycles of
the processor core.
If there are more than one logical processor in a processor
core, CPU_CLK_UNHALTED.THREAD_ANY is supported by
programming IA32_FIXED_CTR_CTRL[bit 6]AnyThread = 1.
The core frequency may change from time to time due to
transitions associated with Enhanced Intel SpeedStep
Technology or TM2. For this reason this event may have a
changing ratio with regards to time.
19-2 Vol. 3B
PERFORMANCE-MONITORING EVENTS
Table 19-2. Fixed-Function Performance Counter and Pre-defined Performance Events (Contd.)
Fixed-Function Performance
Counter
Address
Event Mask Mnemonic
Description
IA32_PERF_FIXED_CTR2
30BH
CPU_CLK_UNHALTED.REF
This event counts the number of reference cycles when the
core is not in a halt state and not in a TM stop-clock state.
The core enters the halt state when it is running the HLT
instruction or the MWAIT instruction.
This event is not affected by core frequency changes (e.g.,
P states) but counts at the same frequency as the time
stamp counter. This event can approximate elapsed time
while the core was not in a halt state and not in a TM stopclock state.
19.2
PERFORMANCE MONITORING EVENTS FOR 6TH GENERATION INTEL®
CORE™ PROCESSOR
6th Generation Intel® Core™ processors are based on the Skylake microarchitecture. They support the architectural performance-monitoring events listed in Table 19-1. Fixed counters in the core PMU support the architecture
events defined in Table 19-2. Non-architectural performance-monitoring events in the processor core are listed in
Table 19-3. The events in Table 19-3 apply to processors with CPUID signature of DisplayFamily_DisplayModel
encoding with the following values: 06_4EH and 06_5EH. Table 19-8 lists performance events supporting Intel TSX
(see Section 18.11.5) and are applicable to processors based on Skylake microarchitecture. Where Skylake microarchitecture implements TSX-related event semantics that differ from Table 19-8, they are listed in Table 19-4.
The comment column in Table 19-3 uses abbreviated letters to indicate additional conditions applicable to the
Event Mask Mnemonic. For event umasks listed in Table 19-3 that do not show “AnyT”, users should refrain from
programming “AnyThread =1” in IA32_PERF_EVTSELx.
Table 19-3. Non-Architectural Performance Events of the Processor Core Supported by Skylake Microarchitecture
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
03H
02H
LD_BLOCKS.STORE_FORWARD
Loads blocked by overlapping with store buffer that
cannot be forwarded.
03H
08H
LD_BLOCKS.NO_SR
The number of times that split load operations are
temporarily blocked because all resources for handling
the split accesses are in use.
07H
01H
LD_BLOCKS_PARTIAL.ADDRESS
_ALIAS
False dependencies in MOB due to partial compare on
address.
08H
01H
DTLB_LOAD_MISSES.MISS_CAUS Load misses in all TLB levels that cause a page walk of
ES_A_WALK
any page size.
08H
0EH
DTLB_LOAD_MISSES.WALK_COM Load misses in all TLB levels causes a page walk that
PLETED
completes. (All page sizes.)
08H
10H
DTLB_LOAD_MISSES.WALK_PEN Counts 1 per cycle for each PMH that is busy with a
DING
page walk for a load.
08H
10H
DTLB_LOAD_MISSES.WALK_ACTI Cycles when at least one PMH is busy with a walk for a CMSK1
VE
load.
08H
20H
DTLB_LOAD_MISSES.STLB_HIT
Loads that miss the DTLB but hit STLB.
0DH
01H
INT_MISC.RECOVERY_CYCLES
Core cycles the allocator was stalled due to recovery
from earlier machine clear event for this thread (for
example, misprediction or memory order conflict).
Comment
Vol. 3B 19-3
PERFORMANCE-MONITORING EVENTS
Table 19-3. Non-Architectural Performance Events of the Processor Core Supported by Skylake Microarchitecture
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
0DH
01H
INT_MISC.RECOVERY_CYCLES_A
NY
Core cycles the allocator was stalled due to recovery
from earlier machine clear event for any logical thread
in this processor core.
AnyT
0DH
80H
INT_MISC.CLEAR_RESTEER_CYC
LES
Cycles the issue-stage is waiting for front end to fetch
from resteered path following branch misprediction or
machine clear events.
0EH
01H
UOPS_ISSUED.ANY
The number of Uops issued by the RAT to RS.
0EH
01H
UOPS_ISSUED.STALL_CYCLES
Cycles when the RAT does not issue uops to RS for the CMSK1, INV
thread.
0EH
02H
UOPS_ISSUED.VECTOR_WIDTH_ Uops inserted at issue-stage in order to preserve upper
MISMATCH
bits of vector registers.
0EH
20H
UOPS_ISSUED.SLOW_LEA
Number of slow LEA or similar uops allocated. Such uop
has 3 sources (for example, 2 sources + immediate)
regardless of whether it is a result of LEA instruction or
not.
14H
01H
ARITH.FPU_DIVIDER_ACTIVE
Cycles when divider is busy executing divide or square
root operations. Accounts for FP operations including
integer divides.
24H
21H
L2_RQSTS.DEMAND_DATA_RD_
MISS
Demand Data Read requests that missed L2, no rejects.
24H
22H
L2_RQSTS.RFO_MISS
RFO requests that missed L2.
24H
24H
L2_RQSTS.CODE_RD_MISS
L2 cache misses when fetching instructions.
24H
27H
L2_RQSTS.ALL_DEMAND_MISS
Demand requests that missed L2.
24H
38H
L2_RQSTS.PF_MISS
Requests from the L1/L2/L3 hardware prefetchers or
load software prefetches that miss L2 cache.
24H
3FH
L2_RQSTS.MISS
All requests that missed L2.
24H
41H
L2_RQSTS.DEMAND_DATA_RD_
HIT
Demand Data Read requests that hit L2 cache.
24H
42H
L2_RQSTS.RFO_HIT
RFO requests that hit L2 cache.
24H
44H
L2_RQSTS.CODE_RD_HIT
L2 cache hits when fetching instructions.
24H
D8H
L2_RQSTS.PF_HIT
Prefetches that hit L2.
24H
E1H
L2_RQSTS.ALL_DEMAND_DATA
_RD
All demand data read requests to L2.
24H
E2H
L2_RQSTS.ALL_RFO
All L RFO requests to L2.
24H
E4H
L2_RQSTS.ALL_CODE_RD
All L2 code requests.
24H
E7H
L2_RQSTS.ALL_DEMAND_REFE
RENCES
All demand requests to L2.
24H
F8H
L2_RQSTS.ALL_PF
All requests from the L1/L2/L3 hardware prefetchers
or load software prefetches.
24H
EFH
L2_RQSTS.REFERENCES
All requests to L2.
2EH
4FH
LONGEST_LAT_CACHE.REFEREN This event counts requests originating from the core
CE
that reference a cache line in the L3 cache.
See Table 19-1.
2EH
41H
LONGEST_LAT_CACHE.MISS
This event counts each cache miss condition for
references to the L3 cache.
See Table 19-1.
3CH
00H
CPU_CLK_UNHALTED.THREAD_
P
Cycles while the logical processor is not in a halt state.
See Table 19-1.
19-4 Vol. 3B
PERFORMANCE-MONITORING EVENTS
Table 19-3. Non-Architectural Performance Events of the Processor Core Supported by Skylake Microarchitecture
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
3CH
00H
CPU_CLK_UNHALTED.THREAD_
P_ANY
Cycles while at least one logical processor is not in a
halt state.
AnyT
3CH
01H
CPU_CLK_THREAD_UNHALTED.
REF_XCLK
Reference cycles when the logical processor is
unhalted (counts at 100 MHz rate).
See Table 19-1.
3CH
01H
CPU_CLK_THREAD_UNHALTED.
REF_XCLK_ANY
Reference cycles when at least one logical processor in AnyT
the processor core is unhalted (counts at 100 MHz
rate).
3CH
02H
CPU_CLK_THREAD_UNHALTED.
ONE_THREAD_ACTIVE
Count XClk pulses when this thread is unhalted and the
other thread is halted.
48H
01H
L1D_PEND_MISS.PENDING
Increments the number of outstanding L1D misses
every cycle.
48H
01H
L1D_PEND_MISS.PENDING_CYCL Cycles with at least one outstanding L1D misses from
ES
this logical processor.
CMSK1
48H
01H
L1D_PEND_MISS.PENDING_CYCL Cycles with at least one outstanding L1D misses from
ES_ANY
any logical processor in this core.
CMSK1, AnyT
48H
02H
L1D_PEND_MISS.FB_FULL
49H
01H
DTLB_STORE_MISSES.MISS_CAU Store misses in all TLB levels that cause page walks.
SES_A_WALK
49H
0EH
DTLB_STORE_MISSES.WALK_CO Counts completed page walks in any TLB levels due to
MPLETED
store misses (all page sizes).
49H
10H
DTLB_STORE_MISSES.WALK_PE
NDING
49H
10H
DTLB_STORE_MISSES.WALK_AC Cycles when at least one PMH is busy with a page walk CMSK1
TIVE
for a store.
49H
20H
DTLB_STORE_MISSES.STLB_HIT Store misses that missed DTLB but hit STLB.
4CH
01H
LOAD_HIT_PRE.HW_PF
Demand load dispatches that hit fill buffer allocated for
software prefetch.
4FH
10H
EPT.WALK_PENDING
Counts 1 per cycle for each PMH that is busy with an
EPT walk for any request type.
51H
01H
L1D.REPLACEMENT
Counts the number of lines brought into the L1 data
cache.
Number of times a request needed a FB entry but there
was no entry available for it. That is, the FB
unavailability was the dominant reason for blocking the
request. A request includes cacheable/uncacheable
demand that is load, store or SW prefetch. HWP are
excluded.
Counts 1 per cycle for each PMH that is busy with a
page walk for a store.
5EH
01H
RS_EVENTS.EMPTY_CYCLES
Cycles the RS is empty for the thread.
5EH
01H
RS_EVENTS.EMPTY_END
Counts end of periods where the Reservation Station
(RS) was empty. Could be useful to precisely locate
Front-end Latency Bound issues.
60H
01H
OFFCORE_REQUESTS_OUTSTAN Increment each cycle of the number of offcore
DING.DEMAND_DATA_RD
outstanding Demand Data Read transactions in SQ to
uncore.
60H
01H
OFFCORE_REQUESTS_OUTSTAN Cycles with at least one offcore outstanding Demand
DING.CYCLES_WITH_DEMAND_D Data Read transactions in SQ to uncore.
ATA_RD
60H
01H
OFFCORE_REQUESTS_OUTSTAN Cycles with at least 6 offcore outstanding Demand Data CMSK6
DING.DEMAND_DATA_RD_GE_6 Read transactions in SQ to uncore.
CMSK1, INV
CMSK1
Vol. 3B 19-5
PERFORMANCE-MONITORING EVENTS
Table 19-3. Non-Architectural Performance Events of the Processor Core Supported by Skylake Microarchitecture
Event
Num.
Umask
Value
60H
02H
OFFCORE_REQUESTS_OUTSTAN Increment each cycle of the number of offcore
DING.DEMAND_CODE_RD
outstanding demand code read transactions in SQ to
uncore.
60H
02H
OFFCORE_REQUESTS_OUTSTAN Cycles with at least one offcore outstanding demand
DING.CYCLES_WITH_DEMAND_C code read transactions in SQ to uncore.
ODE_RD
60H
04H
OFFCORE_REQUESTS_OUTSTAN Increment each cycle of the number of offcore
DING.DEMAND_RFO
outstanding RFO store transactions in SQ to uncore. Set
Cmask=1 to count cycles.
60H
04H
OFFCORE_REQUESTS_OUTSTAN Cycles with at least one offcore outstanding RFO
DING.CYCLES_WITH_DEMAND_R transactions in SQ to uncore.
FO
60H
08H
OFFCORE_REQUESTS_OUTSTAN Increment each cycle of the number of offcore
DING.ALL_DATA_RD
outstanding cacheable data read transactions in SQ to
uncore. Set Cmask=1 to count cycles.
60H
08H
OFFCORE_REQUESTS_OUTSTAN Cycles with at least one offcore outstanding data read
DING.CYCLES_WITH_DATA_RD
transactions in SQ to uncore.
60H
10H
OFFCORE_REQUESTS_OUTSTAN Increment each cycle of the number of offcore
DING.L3_MISS_DEMAND_DATA_ outstanding demand data read requests from SQ that
RD
missed L3.
60H
10H
OFFCORE_REQUESTS_OUTSTAN Cycles with at least one offcore outstanding demand
DING.CYCLES_WITH_L3_MISS_D data read requests from SQ that missed L3.
EMAND_DATA_RD
CMSK1
60H
10H
OFFCORE_REQUESTS_OUTSTAN Cycles with at least one offcore outstanding demand
DING.L3_MISS_DEMAND_DATA_ data read requests from SQ that missed L3.
RD_GE_6
CMSK6
63H
02H
LOCK_CYCLES.CACHE_LOCK_DU
RATION
Cycles in which the L1D is locked.
79H
04H
IDQ.MITE_UOPS
Increment each cycle # of uops delivered to IDQ from
MITE path.
79H
04H
IDQ.MITE_CYCLES
Cycles when uops are being delivered to IDQ from MITE CMSK1
path.
79H
08H
IDQ.DSB_UOPS
Increment each cycle. # of uops delivered to IDQ from
DSB path.
79H
08H
IDQ.DSB_CYCLES
Cycles when uops are being delivered to IDQ from DSB
path.
79H
10H
IDQ.MS_DSB_UOPS
Increment each cycle # of uops delivered to IDQ by DSB
when MS_busy.
79H
18H
IDQ.ALL_DSB_CYCLES_ANY_UO
PS
Cycles DSB is delivered at least one uops.
CMSK1
CMSK4
Event Mask Mnemonic
Description
Comment
CMSK1
CMSK1
CMSK1
CMSK1
79H
18H
IDQ.ALL_DSB_CYCLES_4_UOPS
Cycles DSB is delivered four uops.
79H
20H
IDQ.MS_MITE_UOPS
Increment each cycle # of uops delivered to IDQ by
MITE when MS_busy.
79H
24H
IDQ.ALL_MITE_CYCLES_ANY_UO Counts cycles MITE is delivered at least one uops.
PS
CMSK1
79H
24H
IDQ.ALL_MITE_CYCLES_4_UOPS
Counts cycles MITE is delivered four uops.
CMSK4
79H
30H
IDQ.MS_UOPS
Increment each cycle # of uops delivered to IDQ while
MS is busy.
19-6 Vol. 3B
PERFORMANCE-MONITORING EVENTS
Table 19-3. Non-Architectural Performance Events of the Processor Core Supported by Skylake Microarchitecture
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
79H
30H
IDQ.MS_SWITCHES
Number of switches from DSB or MITE to MS.
EDG
79H
30H
IDQ.MS_CYCLES
Cycles MS is delivered at least one uops.
CMSK1
80H
04H
ICACHE_16B.IFDATA_STALL
Cycles where a code fetch is stalled due to L1
instruction cache miss.
80H
04H
ICACHE_64B.IFDATA_STALL
Cycles where a code fetch is stalled due to L1
instruction cache tag miss.
83H
01H
ICACHE_64B.IFTAG_HIT
Instruction fetch tag lookups that hit in the instruction
cache (L1I). Counts at 64-byte cache-line granularity.
83H
02H
ICACHE_64B.IFTAG_MISS
Instruction fetch tag lookups that miss in the
instruction cache (L1I). Counts at 64-byte cache-line
granularity.
85H
01H
ITLB_MISSES.MISS_CAUSES_A_
WALK
Misses at all ITLB levels that cause page walks.
85H
0EH
ITLB_MISSES.WALK_COMPLETE
D
Counts completed page walks in any TLB level due to
code fetch misses (all page sizes).
85H
10H
ITLB_MISSES.WALK_PENDING
Counts 1 per cycle for each PMH that is busy with a
page walk for an instruction fetch request.
85H
20H
ITLB_MISSES.STLB_HIT
ITLB misses that hit STLB.
87H
01H
ILD_STALL.LCP
Stalls caused by changing prefix length of the
instruction.
9CH
01H
IDQ_UOPS_NOT_DELIVERED.CO
RE
Count issue pipeline slots where no uop was delivered
from the front end to the back end when there is no
back-end stall.
9CH
01H
IDQ_UOPS_NOT_DELIVERED.CYC Cycles which 4 issue pipeline slots had no uop delivered CMSK4
LES_0_UOP_DELIV.CORE
from the front end to the back end when there is no
back-end stall.
9CH
01H
IDQ_UOPS_NOT_DELIVERED.CYC Cycles which “4-n” issue pipeline slots had no uop
LES_LE_n_UOP_DELIV.CORE
delivered from the front end to the back end when
there is no back-end stall.
9CH
01H
IDQ_UOPS_NOT_DELIVERED.CYC Cycles which front end delivered 4 uops or the RAT was CMSK, INV
LES_FE_WAS_OK
stalling FE.
A1H
01H
UOPS_DISPATCHED_PORT.PORT Counts the number of cycles in which a uop is
_0
dispatched to port 0.
A1H
02H
UOPS_DISPATCHED_PORT.PORT Counts the number of cycles in which a uop is
_1
dispatched to port 1.
A1H
04H
UOPS_DISPATCHED_PORT.PORT Counts the number of cycles in which a uop is
_2
dispatched to port 2.
A1H
08H
UOPS_DISPATCHED_PORT.PORT Counts the number of cycles in which a uop is
_3
dispatched to port 3.
A1H
10H
UOPS_DISPATCHED_PORT.PORT Counts the number of cycles in which a uop is
_4
dispatched to port 4.
A1H
20H
UOPS_DISPATCHED_PORT.PORT Counts the number of cycles in which a uop is
_5
dispatched to port 5.
A1H
40H
UOPS_DISPATCHED_PORT.PORT Counts the number of cycles in which a uop is
_6
dispatched to port 6.
A1H
80H
UOPS_DISPATCHED_PORT.PORT Counts the number of cycles in which a uop is
_7
dispatched to port 7.
Set CMSK = 4-n; n = 1,
2, 3
Vol. 3B 19-7
PERFORMANCE-MONITORING EVENTS
Table 19-3. Non-Architectural Performance Events of the Processor Core Supported by Skylake Microarchitecture
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
A2H
01H
RESOURCE_STALLS.ANY
Resource-related stall cycles.
A2H
08H
RESOURCE_STALLS.SB
Cycles stalled due to no store buffers available (not
including draining form sync).
A3H
01H
CYCLE_ACTIVITY.CYCLES_L2_MI
SS
Cycles while L2 cache miss demand load is outstanding. CMSK1
A3H
02H
CYCLE_ACTIVITY.CYCLES_L3_MI
SS
Cycles while L3 cache miss demand load is outstanding. CMSK2
Comment
A3H
04H
CYCLE_ACTIVITY.STALLS_TOTAL Total execution stalls.
CMSK4
A3H
05H
CYCLE_ACTIVITY.STALLS_L2_MI
SS
Execution stalls while L2 cache miss demand load is
outstanding.
CMSK5
A3H
06H
CYCLE_ACTIVITY.STALLS_L3_MI
SS
Execution stalls while L3 cache miss demand load is
outstanding.
CMSK6
A3H
08H
CYCLE_ACTIVITY.CYCLES_L1D_M Cycles while L1 data cache miss demand load is
ISS
outstanding.
CMSK8
A3H
0CH
CYCLE_ACTIVITY.STALLS_L1D_M Execution stalls while L1 data cache miss demand load
ISS
is outstanding.
CMSK12
A3H
10H
CYCLE_ACTIVITY.CYCLES_MEM_
ANY
Cycles while memory subsystem has an outstanding
load.
CMSK16
A3H
14H
CYCLE_ACTIVITY.STALLS_MEM_
ANY
Execution stalls while memory subsystem has an
outstanding load.
CMSK20
A6H
01H
EXE_ACTIVITY.EXE_BOUND_0_P Cycles for which no uops began execution, the
ORTS
Reservation Station was not empty, the Store Buffer
was full and there was no outstanding load.
A6H
02H
EXE_ACTIVITY.1_PORTS_UTIL
Cycles for which one uop began execution on any port,
and the Reservation Station was not empty.
A6H
04H
EXE_ACTIVITY.2_PORTS_UTIL
Cycles for which two uops began execution, and the
Reservation Station was not empty.
A6H
08H
EXE_ACTIVITY.3_PORTS_UTIL
Cycles for which three uops began execution, and the
Reservation Station was not empty.
A6H
04H
EXE_ACTIVITY.4_PORTS_UTIL
Cycles for which four uops began execution, and the
Reservation Station was not empty.
A6H
40H
EXE_ACTIVITY.BOUND_ON_STO
RES
Cycles where the Store Buffer was full and no
outstanding load.
A8H
01H
LSD.UOPS
Number of uops delivered by the LSD.
A8H
01H
LSD.CYCLES_ACTIVE
Cycles with at least one uop delivered by the LSD and
none from the decoder.
A8H
01H
LSD.CYCLES_4_UOPS
Cycles with 4 uops delivered by the LSD and none from CMSK4
the decoder.
ABH
02H
DSB2MITE_SWITCHES.PENALTY
_CYCLES
DSB-to-MITE switch true penalty cycles.
AEH
01H
ITLB.ITLB_FLUSH
Flushing of the Instruction TLB (ITLB) pages, includes
4k/2M/4M pages.
B0H
01H
OFFCORE_REQUESTS.DEMAND_ Demand data read requests sent to uncore.
DATA_RD
B0H
02H
OFFCORE_REQUESTS.DEMAND_ Demand code read requests sent to uncore.
CODE_RD
19-8 Vol. 3B
CMSK1
PERFORMANCE-MONITORING EVENTS
Table 19-3. Non-Architectural Performance Events of the Processor Core Supported by Skylake Microarchitecture
Event
Num.
Umask
Value
B0H
04H
OFFCORE_REQUESTS.DEMAND_ Demand RFO read requests sent to uncore, including
RFO
regular RFOs, locks, ItoM.
B0H
08H
OFFCORE_REQUESTS.ALL_DATA Data read requests sent to uncore (demand and
_RD
prefetch).
B0H
10H
OFFCORE_REQUESTS.L3_MISS_
DEMAND_DATA_RD
B0H
80H
OFFCORE_REQUESTS.ALL_REQU Any memory transaction that reached the SQ.
ESTS
B1H
01H
UOPS_EXECUTED.THREAD
Counts the number of uops that begin execution across
all ports.
B1H
01H
UOPS_EXECUTED.STALL_CYCLE
S
Cycles where there were no uops that began execution. CMSK, INV
B1H
01H
UOPS_EXECUTED.CYCLES_GE_1
_UOP_EXEC
Cycles where there was at least one uop that began
execution.
CMSK1
B1H
01H
UOPS_EXECUTED.CYCLES_GE_2
_UOP_EXEC
Cycles where there were at least two uops that began
execution.
CMSK2
B1H
01H
UOPS_EXECUTED.CYCLES_GE_3
_UOP_EXEC
Cycles where there were at least three uops that began CMSK3
execution.
B1H
01H
UOPS_EXECUTED.CYCLES_GE_4
_UOP_EXEC
Cycles where there were at least four uops that began CMSK4
execution.
B1H
02H
UOPS_EXECUTED.CORE
Counts the number of uops from any logical processor
in this core that begin execution.
B1H
02H
UOPS_EXECUTED.CORE_CYCLES Cycles where there was at least one uop, from any
_GE_1
logical processor in this core, that began execution.
CMSK1
B1H
02H
UOPS_EXECUTED.CORE_CYCLES Cycles where there were at least two uops, from any
_GE_2
logical processor in this core, that began execution.
CMSK2
B1H
02H
UOPS_EXECUTED.CORE_CYCLES Cycles where there were at least three uops, from any
_GE_3
logical processor in this core, that began execution.
CMSK3
B1H
02H
UOPS_EXECUTED.CORE_CYCLES Cycles where there were at least four uops, from any
_GE_4
logical processor in this core, that began execution.
CMSK4
B1H
02H
UOPS_EXECUTED.CORE_CYCLES Cycles where there were no uops from any logical
_NONE
processor in this core that began execution.
CMSK1, INV
Event Mask Mnemonic
Description
Comment
Demand data read requests that missed L3.
B1H
10H
UOPS_EXECUTED.X87
B2H
01H
OFF_CORE_REQUEST_BUFFER.S Offcore requests buffer cannot take more entries for
Q_FULL
this core.
Counts the number of X87 uops that begin execution.
B7H
01H
OFF_CORE_RESPONSE_0
See Section 18.9.5, “Off-core Response Performance
Monitoring”.
Requires MSR 01A6H
BBH
01H
OFF_CORE_RESPONSE_1
See Section 18.9.5, “Off-core Response Performance
Monitoring”.
Requires MSR 01A7H
BDH
01H
TLB_FLUSH.DTLB_THREAD
DTLB flush attempts of the thread-specific entries.
BDH
01H
TLB_FLUSH.STLB_ANY
STLB flush attempts.
C0H
00H
INST_RETIRED.ANY_P
Number of instructions at retirement.
See Table 19-1.
C0H
01H
INST_RETIRED.PREC_DIST
Precise instruction retired event with HW to reduce
effect of PEBS shadow in IP distribution.
PMC1 only;
C0H
01H
INST_RETIRED.TOTAL_CYCLES
Number of cycles using always true condition applied to CMSK10, PS
PEBS instructions retired event.
Vol. 3B 19-9
PERFORMANCE-MONITORING EVENTS
Table 19-3. Non-Architectural Performance Events of the Processor Core Supported by Skylake Microarchitecture
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
C1H
3FH
OTHER_ASSISTS.ANY
Number of times a microcode assist is invoked by HW
other than FP-assist. Examples include AD (page Access
Dirty) and AVX* related assists.
C2H
01H
UOPS_RETIRED.STALL_CYCLES
Cycles without actually retired uops.
CMSK1, INV
C2H
01H
UOPS_RETIRED.TOTAL_CYCLES
Cycles with less than 10 actually retired uops.
CMSK10, INV
C2H
02H
UOPS_RETIRED.RETIRE_SLOTS
Retirement slots used.
C3H
01H
MACHINE_CLEARS.COUNT
Number of machine clears of any type.
C3H
02H
MACHINE_CLEARS.MEMORY_OR
DERING
Counts the number of machine clears due to memory
order conflicts.
C3H
04H
MACHINE_CLEARS.SMC
Number of self-modifying-code machine clears
detected.
C4H
00H
BR_INST_RETIRED.ALL_BRANC
HES
Branch instructions that retired.
See Table 19-1.
C4H
01H
BR_INST_RETIRED.CONDITIONA
L
Counts the number of conditional branch instructions
retired.
PS
C4H
02H
BR_INST_RETIRED.NEAR_CALL
Direct and indirect near call instructions retired.
PS
C4H
04H
BR_INST_RETIRED.ALL_BRANC
HES
Counts the number of branch instructions retired.
PS
C4H
08H
BR_INST_RETIRED.NEAR_RETU
RN
Counts the number of near return instructions retired.
PS
C4H
10H
BR_INST_RETIRED.NOT_TAKEN
Counts the number of not taken branch instructions
retired.
C4H
20H
BR_INST_RETIRED.NEAR_TAKE
N
Number of near taken branches retired.
PS
C4H
40H
BR_INST_RETIRED.FAR_BRANC
H
Number of far branches retired.
PS
C5H
00H
BR_MISP_RETIRED.ALL_BRANC
HES
Mispredicted branch instructions at retirement.
See Table 19-1.
C5H
01H
BR_MISP_RETIRED.CONDITIONA Mispredicted conditional branch instructions retired.
L
PS
C5H
04H
BR_MISP_RETIRED.ALL_BRANC
HES
Mispredicted macro branch instructions retired.
PS
C5H
20H
BR_MISP_RETIRED.NEAR_TAKE
N
Number of near branch instructions retired that were
mispredicted and taken.
PS
C6H
01H
FRONTEND_RETIRED.DSB_MISS
Retired instructions which experienced DSB miss.
Specify MSR_PEBS_FRONTEND.EVTSEL=11H.
PS
C6H
01H
FRONTEND_RETIRED.L1I_MISS
Retired instructions which experienced instruction L1
cache true miss. Specify
MSR_PEBS_FRONTEND.EVTSEL=12H.
PS
C6H
01H
FRONTEND_RETIRED.L2_MISS
Retired instructions which experienced L2 cache true
miss. Specify MSR_PEBS_FRONTEND.EVTSEL=13H.
PS
C6H
01H
FRONTEND_RETIRED.ITLB_MISS Retired instructions which experienced ITLB true miss.
Specify MSR_PEBS_FRONTEND.EVTSEL=14H.
C6H
01H
FRONTEND_RETIRED.STLB_MIS
S
19-10 Vol. 3B
Comment
CMSK1, EDG
PS
Retired instructions which experienced STLB true miss. PS
Specify MSR_PEBS_FRONTEND.EVTSEL=15H.
PERFORMANCE-MONITORING EVENTS
Table 19-3. Non-Architectural Performance Events of the Processor Core Supported by Skylake Microarchitecture
Event
Num.
Umask
Value
C6H
01H
FRONTEND_RETIRED.LATENCY_ Retired instructions that are fetched after an interval
GE_16
where the front end delivered no uops for at least 16
cycles. Specify the following fields in
MSR_PEBS_FRONTEND: EVTSEL=16H,
IDQ_Bubble_Length =16, IDQ_Bubble_Width = 4.
C6H
01H
PS, m = 1, 2, 3
FRONTEND_RETIRED.LATENCY_ Retired instructions that are fetched after an interval
GE_2_BUBBLES_GE_m
where the front end had ‘m’ IDQ slots delivered, no
uops for at least 2 cycles. Specify the following fields in
MSR_PEBS_FRONTEND: EVTSEL=16H,
IDQ_Bubble_Length =2, IDQ_Bubble_Width = m.
C7H
01H
FP_ARITH_INST_RETIRED.SCAL
AR_DOUBLE
Number of double-precision, floating-point, scalar
SSE/AVX computational instructions that are retired.
Each scalar FMA instruction counts as 2.
Software may treat
each count as one DP
FLOP.
C7H
02H
FP_ARITH_INST_RETIRED.SCAL
AR_SINGLE
Number of single-precision, floating-point, scalar
SSE/AVX computational instructions that are retired.
Each scalar FMA instruction counts as 2.
Software may treat
each count as one SP
FLOP.
C7H
04H
FP_ARITH_INST_RETIRED.128B Number of double-precision, floating-point, 128-bit
_PACKED_DOUBLE
SSE/AVX computational instructions that are retired.
Each 128-bit FMA or (V)DPPD instruction counts as 2.
Software may treat
each count as two DP
FLOPs.
C7H
08H
FP_ARITH_INST_RETIRED.128B Number of single-precision, floating-point, 128-bit
_PACKED_SINGLE
SSE/AVX computational instructions that are retired.
Each 128-bit FMA or (V)DPPS instruction counts as 2.
Software may treat
each count as four SP
FLOPs.
C7H
10H
FP_ARITH_INST_RETIRED.256B Number of double-precision, floating-point, 256-bit
_PACKED_DOUBLE
SSE/AVX computational instructions that are retired.
Each 256-bit FMA instruction counts as 2.
Software may treat
each count as four DP
FLOPs.
C7H
20H
FP_ARITH_INST_RETIRED.256B Number of single-precision, floating-point, 256-bit
_PACKED_SINGLE
SSE/AVX computational instructions that are retired.
Each 256-bit FMA or VDPPS instruction counts as 2.
Software may treat
each count as eight SP
FLOPs.
CAH
1EH
FP_ASSIST.ANY
Cycles with any input/output SSE* or FP assists.
CMSK1
CBH
01H
HW_INTERRUPTS.RECEIVED
Number of hardware interrupts received by the
processor.
CDH
01H
MEM_TRANS_RETIRED.LOAD_L
ATENCY
Randomly sampled loads whose latency is above a user Specify threshold in
defined threshold. A small fraction of the overall loads MSR 3F6H.
are sampled due to randomization.
PSDLA
D0H
11H
MEM_INST_RETIRED.STLB_MISS Retired load instructions that miss the STLB.
_LOADS
PSDLA
D0H
12H
MEM_INST_RETIRED.STLB_MISS Retired store instructions that miss the STLB.
_STORES
PSDLA
D0H
21H
MEM_INST_RETIRED.LOCK_LOA
DS
PSDLA
D0H
41H
MEM_INST_RETIRED.SPLIT_LOA Number of load instructions retired with cache-line
DS
splits that may impact performance.
PSDLA
D0H
42H
MEM_INST_RETIRED.SPLIT_STO Number of store instructions retired with line-split.
RES
PSDLA
D0H
81H
MEM_INST_RETIRED.ALL_LOAD
S
All retired load instructions.
PSDLA
D0H
82H
MEM_INST_RETIRED.ALL_STOR
ES
All retired store instructions.
PSDLA
Event Mask Mnemonic
Description
Retired load instructions with locked access.
Comment
PS
Vol. 3B 19-11
PERFORMANCE-MONITORING EVENTS
Table 19-3. Non-Architectural Performance Events of the Processor Core Supported by Skylake Microarchitecture
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
D1H
01H
MEM_LOAD_RETIRED.L1_HIT
Retired load instructions with L1 cache hits as data
sources.
PSDLA
D1H
02H
MEM_LOAD_RETIRED.L2_HIT
Retired load instructions with L2 cache hits as data
sources.
PSDLA
D1H
04H
MEM_LOAD_RETIRED.L3_HIT
Retired load instructions with L3 cache hits as data
sources.
PSDLA
D1H
08H
MEM_LOAD_RETIRED.L1_MISS
Retired load instructions missed L1 cache as data
sources.
PSDLA
D1H
10H
MEM_LOAD_RETIRED.L2_MISS
Retired load instructions missed L2. Unknown data
source excluded.
PSDLA
D1H
20H
MEM_LOAD_RETIRED.L3_MISS
Retired load instructions missed L3. Excludes unknown PSDLA
data source.
D1H
40H
MEM_LOAD_RETIRED.FB_HIT
Retired load instructions where data sources were load PSDLA
uops missed L1 but hit FB due to preceding miss to the
same cache line with data not ready.
D2H
01H
MEM_LOAD_L3_HIT_RETIRED.X
SNP_MISS
Retired load instructions where data sources were L3
hit and cross-core snoop missed in on-pkg core cache.
PSDLA
D2H
02H
MEM_LOAD_L3_HIT_RETIRED.X
SNP_HIT
Retired load Instructions where data sources were L3
and cross-core snoop hits in on-pkg core cache.
PSDLA
D2H
04H
MEM_LOAD_L3_HIT_RETIRED.X
SNP_HITM
Retired load instructions where data sources were HitM PSDLA
responses from shared L3.
D2H
08H
MEM_LOAD_L3_HIT_RETIRED.X
SNP_NONE
Retired load instructions where data sources were hits PSDLA
in L3 without snoops required.
E6H
01H
BACLEARS.ANY
Number of front end re-steers due to BPU
misprediction.
F0H
40H
L2_TRANS.L2_WB
L2 writebacks that access L2 cache.
F1H
07H
L2_LINES_IN.ALL
L2 cache lines filling L2.
CMSK1: Counter Mask = 1 required; CMSK4: CounterMask = 4 required; CMSK6: CounterMask = 6 required; CMSK8: CounterMask = 8
required; CMSK10: CounterMask = 10 required; CMSK12: CounterMask = 12 required; CMSK16: CounterMask = 16 required; CMSK20:
CounterMask = 20 required.
AnyT: AnyThread = 1 required.
INV: Invert = 1 required.
EDG: EDGE = 1 required.
PSDLA: Also supports PEBS and DataLA.
PS: Also supports PEBS.
Table 19-8 lists performance events supporting Intel TSX (see Section 18.11.5) and are applicable to processors
based on Skylake microarchitecture. Where Skylake microarchitecture implements TSX-related event semantics
that differ from Table 19-8, they are listed in Table 19-4.
Table 19-4. Intel® TSX Performance Event Addendum in Processors based on Skylake Microarchitecture
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
54H
02H
TX_MEM.ABORT_CAPACITY
Number of times a transactional abort was signaled due
to a data capacity limitation for transactional reads or
writes.
19-12 Vol. 3B
Comment
PERFORMANCE-MONITORING EVENTS
19.3
PERFORMANCE MONITORING EVENTS FOR THE INTEL® CORE™ M AND 5TH
GENERATION INTEL® CORE™ PROCESSORS
The Intel® Core™ M processors, the 5th generation Intel® Core™ processors and the Intel Xeon processor E3 1200
v4 product family are based on the Broadwell microarchitecture. They support the architectural performancemonitoring events listed in Table 19-1. Non-architectural performance-monitoring events in the processor core are
listed in Table 19-5. The events in Table 19-5 apply to processors with CPUID signature of
DisplayFamily_DisplayModel encoding with the following values: 06_3DH and 06_47H. Table 19-8 lists performance events supporting Intel TSX (see Section 18.11.5) and are available on processors based on Broadwell
microarchitecture. Fixed counters in the core PMU support the architecture events defined in Table 19-2.
Non-architectural performance monitoring events that are located in the uncore sub-system are implementation
specific between different platforms using processors based on Broadwell microarchitecture and with different
DisplayFamily_DisplayModel signatures. Processors with CPUID signature of DisplayFamily_DisplayModel 06_3DH
and 06_47H support uncore performance events listed in Table 19-9.
Table 19-5. Non-Architectural Performance Events of the Processor Core Supported by Broadwell
Microarchitecture
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
03H
02H
LD_BLOCKS.STORE_FORWARD
Loads blocked by overlapping with store buffer that
cannot be forwarded.
03H
08H
LD_BLOCKS.NO_SR
The number of times that split load operations are
temporarily blocked because all resources for
handling the split accesses are in use.
05H
01H
MISALIGN_MEM_REF.LOADS
Speculative cache-line split load uops dispatched to
L1D.
05H
02H
MISALIGN_MEM_REF.STORES
Speculative cache-line split store-address uops
dispatched to L1D.
07H
01H
LD_BLOCKS_PARTIAL.ADDRESS
_ALIAS
False dependencies in MOB due to partial compare
on address.
08H
01H
DTLB_LOAD_MISSES.MISS_CAUS Load misses in all TLB levels that cause a page walk
ES_A_WALK
of any page size.
08H
02H
DTLB_LOAD_MISSES.WALK_COM Completed page walks due to demand load misses
PLETED_4K
that caused 4K page walks in any TLB levels.
08H
10H
DTLB_LOAD_MISSES.WALK_DUR Cycle PMH is busy with a walk.
ATION
08H
20H
DTLB_LOAD_MISSES.STLB_HIT_ Load misses that missed DTLB but hit STLB (4K).
4K
0DH
03H
INT_MISC.RECOVERY_CYCLES
Cycles waiting to recover after Machine Clears
except JEClear. Set Cmask= 1.
Set Edge to count
occurrences.
0EH
01H
UOPS_ISSUED.ANY
Increments each cycle the # of uops issued by the
RAT to RS. Set Cmask = 1, Inv = 1, Any= 1to count
stalled cycles of this core.
Set Cmask = 1, Inv = 1to
count stalled cycles.
0EH
10H
UOPS_ISSUED.FLAGS_MERGE
Number of flags-merge uops allocated. Such uops
add delay.
0EH
20H
UOPS_ISSUED.SLOW_LEA
Number of slow LEA or similar uops allocated. Such
uop has 3 sources (for example, 2 sources +
immediate) regardless of whether it is a result of
LEA instruction or not.
0EH
40H
UOPS_ISSUED.SiNGLE_MUL
Number of multiply packed/scalar single precision
uops allocated.
Comment
Vol. 3B 19-13
PERFORMANCE-MONITORING EVENTS
Table 19-5. Non-Architectural Performance Events of the Processor Core Supported by Broadwell
Microarchitecture (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
14H
01H
ARITH.FPU_DIV_ACTIVE
Cycles when divider is busy executing divide
operations.
24H
21H
L2_RQSTS.DEMAND_DATA_RD_ Demand data read requests that missed L2, no
MISS
rejects.
24H
41H
L2_RQSTS.DEMAND_DATA_RD_ Demand data read requests that hit L2 cache.
HIT
24H
50H
L2_RQSTS.L2_PF_HIT
Counts all L2 HW prefetcher requests that hit L2.
24H
30H
L2_RQSTS.L2_PF_MISS
Counts all L2 HW prefetcher requests that missed
L2.
24H
E1H
L2_RQSTS.ALL_DEMAND_DATA
_RD
Counts any demand and L1 HW prefetch data load
requests to L2.
24H
E2H
L2_RQSTS.ALL_RFO
Counts all L2 store RFO requests.
Comment
24H
E4H
L2_RQSTS.ALL_CODE_RD
Counts all L2 code requests.
24H
F8H
L2_RQSTS.ALL_PF
Counts all L2 HW prefetcher requests.
27H
50H
L2_DEMAND_RQSTS.WB_HIT
Not rejected writebacks that hit L2 cache.
2EH
4FH
LONGEST_LAT_CACHE.REFEREN This event counts requests originating from the core See Table 19-1.
CE
that reference a cache line in the last level cache.
2EH
41H
LONGEST_LAT_CACHE.MISS
This event counts each cache miss condition for
references to the last level cache.
3CH
00H
CPU_CLK_UNHALTED.THREAD_
P
Counts the number of thread cycles while the thread See Table 19-1.
is not in a halt state. The thread enters the halt state
when it is running the HLT instruction. The core
frequency may change from time to time due to
power or thermal throttling.
3CH
01H
CPU_CLK_THREAD_UNHALTED.
REF_XCLK
Increments at the frequency of XCLK (100 MHz)
when not halted.
See Table 19-1.
48H
01H
L1D_PEND_MISS.PENDING
Increments the number of outstanding L1D misses
every cycle. Set Cmask = 1 and Edge =1 to count
occurrences.
Counter 2 only.
49H
01H
DTLB_STORE_MISSES.MISS_CAU Miss in all TLB levels causes an page walk of any
SES_A_WALK
page size (4K/2M/4M/1G).
49H
02H
DTLB_STORE_MISSES.WALK_CO Completed page walks due to store misses in one or
MPLETED_4K
more TLB levels of 4K page structure.
49H
10H
DTLB_STORE_MISSES.WALK_DU Cycles PMH is busy with this walk.
RATION
49H
20H
DTLB_STORE_MISSES.STLB_HIT Store misses that missed DTLB but hit STLB (4K).
_4K
4CH
02H
LOAD_HIT_PRE.HW_PF
Non-SW-prefetch load dispatches that hit fill buffer
allocated for H/W prefetch.
4FH
10H
EPT.WALK_CYCLES
Cycles of Extended Page Table walks.
51H
01H
L1D.REPLACEMENT
Counts the number of lines brought into the L1 data
cache.
58H
04H
MOVE_ELIMINATION.INT_NOT_E Number of integer move elimination candidate uops
LIMINATED
that were not eliminated.
19-14 Vol. 3B
See Table 19-1.
Set Cmask = 1 to count
cycles.
PERFORMANCE-MONITORING EVENTS
Table 19-5. Non-Architectural Performance Events of the Processor Core Supported by Broadwell
Microarchitecture (Contd.)
Event
Num.
Umask
Value
58H
08H
MOVE_ELIMINATION.SIMD_NOT_ Number of SIMD move elimination candidate uops
ELIMINATED
that were not eliminated.
58H
01H
MOVE_ELIMINATION.INT_ELIMIN Number of integer move elimination candidate uops
ATED
that were eliminated.
58H
02H
MOVE_ELIMINATION.SIMD_ELIMI Number of SIMD move elimination candidate uops
NATED
that were eliminated.
5CH
01H
CPL_CYCLES.RING0
5CH
02H
CPL_CYCLES.RING123
Unhalted core cycles when the thread is not in ring 0.
5EH
01H
RS_EVENTS.EMPTY_CYCLES
Cycles the RS is empty for the thread.
60H
01H
OFFCORE_REQUESTS_OUTSTAN Offcore outstanding demand data read transactions
DING.DEMAND_DATA_RD
in SQ to uncore. Set Cmask=1 to count cycles.
60H
02H
OFFCORE_REQUESTS_OUTSTAN Offcore outstanding demand code read transactions Use only when HTT is
DING.DEMAND_CODE_RD
in SQ to uncore. Set Cmask=1 to count cycles.
off.
60H
04H
OFFCORE_REQUESTS_OUTSTAN Offcore outstanding RFO store transactions in SQ to Use only when HTT is
DING.DEMAND_RFO
uncore. Set Cmask=1 to count cycles.
off.
60H
08H
OFFCORE_REQUESTS_OUTSTAN Offcore outstanding cacheable data read
DING.ALL_DATA_RD
transactions in SQ to uncore. Set Cmask=1 to count
cycles.
63H
01H
LOCK_CYCLES.SPLIT_LOCK_UC_
LOCK_DURATION
Cycles in which the L1D and L2 are locked, due to a
UC lock or split lock.
63H
02H
LOCK_CYCLES.CACHE_LOCK_DU
RATION
Cycles in which the L1D is locked.
79H
02H
IDQ.EMPTY
Counts cycles the IDQ is empty.
79H
04H
IDQ.MITE_UOPS
Increment each cycle # of uops delivered to IDQ from Can combine Umask 04H
MITE path. Set Cmask = 1 to count cycles.
and 20H.
79H
08H
IDQ.DSB_UOPS
Increment each cycle # of uops delivered to IDQ from Can combine Umask 08H
DSB path. Set Cmask = 1 to count cycles.
and 10H.
79H
10H
IDQ.MS_DSB_UOPS
Increment each cycle # of uops delivered to IDQ
when MS_busy by DSB. Set Cmask = 1 to count
cycles. Add Edge=1 to count # of delivery.
Can combine Umask 04H,
08H.
79H
20H
IDQ.MS_MITE_UOPS
Increment each cycle # of uops delivered to IDQ
when MS_busy by MITE. Set Cmask = 1 to count
cycles.
Can combine Umask 04H,
08H.
79H
30H
IDQ.MS_UOPS
Increment each cycle # of uops delivered to IDQ from Can combine Umask 04H,
MS by either DSB or MITE. Set Cmask = 1 to count
08H.
cycles.
79H
18H
IDQ.ALL_DSB_CYCLES_ANY_UO
PS
Counts cycles DSB is delivered at least one uops. Set
Cmask = 1.
79H
18H
IDQ.ALL_DSB_CYCLES_4_UOPS
Counts cycles DSB is delivered four uops. Set Cmask
= 4.
79H
24H
IDQ.ALL_MITE_CYCLES_ANY_UO Counts cycles MITE is delivered at least one uop. Set
PS
Cmask = 1.
79H
24H
IDQ.ALL_MITE_CYCLES_4_UOPS Counts cycles MITE is delivered four uops. Set Cmask
= 4.
79H
3CH
IDQ.MITE_ALL_UOPS
Event Mask Mnemonic
Description
Unhalted core cycles when the thread is in ring 0.
Comment
Use Edge to count
transition.
Use only when HTT is
off.
Use only when HTT is
off.
# of uops delivered to IDQ from any path.
Vol. 3B 19-15
PERFORMANCE-MONITORING EVENTS
Table 19-5. Non-Architectural Performance Events of the Processor Core Supported by Broadwell
Microarchitecture (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
80H
02H
ICACHE.MISSES
Number of Instruction Cache, Streaming Buffer and
Victim Cache Misses. Includes UC accesses.
85H
01H
ITLB_MISSES.MISS_CAUSES_A_
WALK
Misses in ITLB that cause a page walk of any page
size.
85H
02H
ITLB_MISSES.WALK_COMPLETE
D_4K
Completed page walks due to misses in ITLB 4K page
entries.
85H
10H
ITLB_MISSES.WALK_DURATION
Cycle PMH is busy with a walk.
85H
20H
ITLB_MISSES.STLB_HIT_4K
ITLB misses that hit STLB (4K).
87H
01H
ILD_STALL.LCP
Stalls caused by changing prefix length of the
instruction.
88H
01H
BR_INST_EXEC.COND
Qualify conditional near branch instructions
executed, but not necessarily retired.
Must combine with
umask 40H, 80H.
88H
02H
BR_INST_EXEC.DIRECT_JMP
Qualify all unconditional near branch instructions
excluding calls and indirect branches.
Must combine with
umask 80H.
88H
04H
BR_INST_EXEC.INDIRECT_JMP_
NON_CALL_RET
Qualify executed indirect near branch instructions
that are not calls nor returns.
Must combine with
umask 80H.
88H
08H
BR_INST_EXEC.RETURN_NEAR
Qualify indirect near branches that have a return
mnemonic.
Must combine with
umask 80H.
88H
10H
BR_INST_EXEC.DIRECT_NEAR_C Qualify unconditional near call branch instructions,
ALL
excluding non call branch, executed.
88H
20H
BR_INST_EXEC.INDIRECT_NEAR Qualify indirect near calls, including both register and Must combine with
_CALL
memory indirect, executed.
umask 80H.
88H
40H
BR_INST_EXEC.NONTAKEN
Qualify non-taken near branches executed.
88H
80H
BR_INST_EXEC.TAKEN
Qualify taken near branches executed. Must combine
with 01H,02H, 04H, 08H, 10H, 20H.
88H
FFH
BR_INST_EXEC.ALL_BRANCHES Counts all near executed branches (not necessarily
retired).
89H
01H
BR_MISP_EXEC.COND
Qualify conditional near branch instructions
mispredicted.
Must combine with
umask 40H, 80H.
89H
04H
BR_MISP_EXEC.INDIRECT_JMP_
NON_CALL_RET
Qualify mispredicted indirect near branch
instructions that are not calls nor returns.
Must combine with
umask 80H.
89H
08H
BR_MISP_EXEC.RETURN_NEAR
Qualify mispredicted indirect near branches that
have a return mnemonic.
Must combine with
umask 80H.
89H
10H
BR_MISP_EXEC.DIRECT_NEAR_C Qualify mispredicted unconditional near call branch
ALL
instructions, excluding non call branch, executed.
Must combine with
umask 80H.
89H
20H
BR_MISP_EXEC.INDIRECT_NEAR Qualify mispredicted indirect near calls, including
_CALL
both register and memory indirect, executed.
Must combine with
umask 80H.
89H
40H
BR_MISP_EXEC.NONTAKEN
Qualify mispredicted non-taken near branches
executed.
Applicable to umask 01H
only.
89H
80H
BR_MISP_EXEC.TAKEN
Qualify mispredicted taken near branches executed.
Must combine with 01H,02H, 04H, 08H, 10H, 20H.
89H
FFH
BR_MISP_EXEC.ALL_BRANCHES Counts all near executed branches (not necessarily
retired).
19-16 Vol. 3B
Comment
Must combine with
umask 80H.
Applicable to umask 01H
only.
PERFORMANCE-MONITORING EVENTS
Table 19-5. Non-Architectural Performance Events of the Processor Core Supported by Broadwell
Microarchitecture (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
9CH
01H
IDQ_UOPS_NOT_DELIVERED.CO
RE
Count issue pipeline slots where no uop was
delivered from the front end to the back end when
there is no back end stall.
Use Cmask to qualify uop
b/w.
A1H
01H
UOPS_DISPATCHED_PORT.PORT Counts the number of cycles in which a uop is
_0
dispatched to port 0.
Set AnyThread to count
per core.
A1H
02H
UOPS_DISPATCHED_PORT.PORT Counts the number of cycles in which a uop is
_1
dispatched to port 1.
Set AnyThread to count
per core.
A1H
04H
UOPS_DISPATCHED_PORT.PORT Counts the number of cycles in which a uop is
_2
dispatched to port 2.
Set AnyThread to count
per core.
A1H
08H
UOPS_DISPATCHED_PORT.PORT Counts the number of cycles in which a uop is
_3
dispatched to port 3.
Set AnyThread to count
per core.
A1H
10H
UOPS_DISPATCHED_PORT.PORT Counts the number of cycles in which a uop is
_4
dispatched to port 4.
Set AnyThread to count
per core.
A1H
20H
UOPS_DISPATCHED_PORT.PORT Counts the number of cycles in which a uop is
_5
dispatched to port 5.
Set AnyThread to count
per core.
A1H
40H
UOPS_DISPATCHED_PORT.PORT Counts the number of cycles in which a uop is
_6
dispatched to port 6.
Set AnyThread to count
per core.
A1H
80H
UOPS_DISPATCHED_PORT.PORT Counts the number of cycles in which a uop is
_7
dispatched to port 7.
Set AnyThread to count
per core.
A2H
01H
RESOURCE_STALLS.ANY
Cycles Allocation is stalled due to resource related
reason.
A2H
04H
RESOURCE_STALLS.RS
Cycles stalled due to no eligible RS entry available.
A2H
08H
RESOURCE_STALLS.SB
Cycles stalled due to no store buffers available (not
including draining form sync).
A2H
10H
RESOURCE_STALLS.ROB
Cycles stalled due to re-order buffer full.
A8H
01H
LSD.UOPS
Number of uops delivered by the LSD.
ABH
02H
DSB2MITE_SWITCHES.PENALTY
_CYCLES
Cycles of delay due to Decode Stream Buffer to MITE
switches.
AEH
01H
ITLB.ITLB_FLUSH
Counts the number of ITLB flushes; includes
4k/2M/4M pages.
B0H
01H
OFFCORE_REQUESTS.DEMAND_ Demand data read requests sent to uncore.
DATA_RD
Use only when HTT is
off.
B0H
02H
OFFCORE_REQUESTS.DEMAND_ Demand code read requests sent to uncore.
CODE_RD
Use only when HTT is
off.
B0H
04H
OFFCORE_REQUESTS.DEMAND_ Demand RFO read requests sent to uncore, including Use only when HTT is
RFO
regular RFOs, locks, ItoM.
off.
B0H
08H
OFFCORE_REQUESTS.ALL_DATA Data read requests sent to uncore (demand and
_RD
prefetch).
Use only when HTT is
off.
B1H
01H
UOPS_EXECUTED.THREAD
Counts total number of uops to be executed perlogical-processor each cycle.
Use Cmask to count stall
cycles.
B1H
02H
UOPS_EXECUTED.CORE
Counts total number of uops to be executed per-core Do not need to set ANY.
each cycle.
B7H
01H
OFF_CORE_RESPONSE_0
See Section 18.9.5, “Off-core Response Performance Requires MSR 01A6H.
Monitoring”.
Vol. 3B 19-17
PERFORMANCE-MONITORING EVENTS
Table 19-5. Non-Architectural Performance Events of the Processor Core Supported by Broadwell
Microarchitecture (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
BBH
01H
OFF_CORE_RESPONSE_1
See Section 18.9.5, “Off-core Response Performance Requires MSR 01A7H.
Monitoring”.
BCH
11H
PAGE_WALKER_LOADS.DTLB_L1 Number of DTLB page walker loads that hit in the
L1+FB.
BCH
21H
PAGE_WALKER_LOADS.ITLB_L1
BCH
12H
PAGE_WALKER_LOADS.DTLB_L2 Number of DTLB page walker loads that hit in the L2.
BCH
22H
PAGE_WALKER_LOADS.ITLB_L2
BCH
14H
PAGE_WALKER_LOADS.DTLB_L3 Number of DTLB page walker loads that hit in the L3.
BCH
24H
PAGE_WALKER_LOADS.ITLB_L3
Number of ITLB page walker loads that hit in the L3.
BCH
18H
PAGE_WALKER_LOADS.DTLB_M
EMORY
Number of DTLB page walker loads from memory.
C0H
00H
INST_RETIRED.ANY_P
Number of instructions at retirement.
See Table 19-1.
C0H
01H
INST_RETIRED.PREC_DIST
Precise instruction retired event with HW to reduce
effect of PEBS shadow in IP distribution.
PMC1 only.
C0H
02H
INST_RETIRED.X87
FP operations retired. X87 FP operations that have
no exceptions.
C1H
08H
OTHER_ASSISTS.AVX_TO_SSE
Number of transitions from AVX-256 to legacy SSE
when penalty applicable.
C1H
10H
OTHER_ASSISTS.SSE_TO_AVX
Number of transitions from SSE to AVX-256 when
penalty applicable.
C1H
40H
OTHER_ASSISTS.ANY_WB_ASSI
ST
Number of microcode assists invoked by HW upon
uop writeback.
C2H
01H
UOPS_RETIRED.ALL
Comment
Number of ITLB page walker loads that hit in the
L1+FB.
Number of ITLB page walker loads that hit in the L2.
Counts the number of micro-ops retired.
Use cmask=1 and invert to count active cycles or
stalled cycles.
Supports PEBS and
DataLA, use Any=1 for
core granular.
C2H
02H
UOPS_RETIRED.RETIRE_SLOTS
Counts the number of retirement slots used each
cycle.
C3H
01H
MACHINE_CLEARS.CYCLES
Counts cycles while a machine clears stalled forward
progress of a logical processor or a processor core.
C3H
02H
MACHINE_CLEARS.MEMORY_OR Counts the number of machine clears due to memory
DERING
order conflicts.
C3H
04H
MACHINE_CLEARS.SMC
Number of self-modifying-code machine clears
detected.
C3H
20H
MACHINE_CLEARS.MASKMOV
Counts the number of executed AVX masked load
operations that refer to an illegal address range with
the mask bits set to 0.
C4H
00H
BR_INST_RETIRED.ALL_BRANC
HES
Branch instructions at retirement.
C4H
01H
BR_INST_RETIRED.CONDITIONA Counts the number of conditional branch instructions Supports PEBS.
L
retired.
C4H
02H
BR_INST_RETIRED.NEAR_CALL
Direct and indirect near call instructions retired.
Supports PEBS.
C4H
04H
BR_INST_RETIRED.ALL_BRANC
HES
Counts the number of branch instructions retired.
Supports PEBS.
19-18 Vol. 3B
Supports PEBS.
See Table 19-1.
PERFORMANCE-MONITORING EVENTS
Table 19-5. Non-Architectural Performance Events of the Processor Core Supported by Broadwell
Microarchitecture (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
C4H
08H
BR_INST_RETIRED.NEAR_RETU
RN
Counts the number of near return instructions
retired.
Supports PEBS.
C4H
10H
BR_INST_RETIRED.NOT_TAKEN
Counts the number of not taken branch instructions
retired.
C4H
20H
BR_INST_RETIRED.NEAR_TAKE
N
Number of near taken branches retired.
C4H
40H
BR_INST_RETIRED.FAR_BRANC
H
Number of far branches retired.
C5H
00H
BR_MISP_RETIRED.ALL_BRANC
HES
Mispredicted branch instructions at retirement.
C5H
01H
BR_MISP_RETIRED.CONDITIONA Mispredicted conditional branch instructions retired.
L
Supports PEBS.
C5H
04H
BR_MISP_RETIRED.ALL_BRANC
HES
Mispredicted macro branch instructions retired.
Supports PEBS.
CAH
02H
FP_ASSIST.X87_OUTPUT
Number of X87 FP assists due to output values.
CAH
04H
FP_ASSIST.X87_INPUT
Number of X87 FP assists due to input values.
Supports PEBS.
See Table 19-1.
CAH
08H
FP_ASSIST.SIMD_OUTPUT
Number of SIMD FP assists due to output values.
CAH
10H
FP_ASSIST.SIMD_INPUT
Number of SIMD FP assists due to input values.
CAH
1EH
FP_ASSIST.ANY
Cycles with any input/output SSE* or FP assists.
CCH
20H
ROB_MISC_EVENTS.LBR_INSER
TS
Count cases of saving new LBR records by hardware.
CDH
01H
MEM_TRANS_RETIRED.LOAD_L
ATENCY
Randomly sampled loads whose latency is above a
Specify threshold in MSR
user defined threshold. A small fraction of the overall 3F6H.
loads are sampled due to randomization.
D0H
11H
MEM_UOPS_RETIRED.STLB_MIS Retired load uops that miss the STLB.
S_LOADS
Supports PEBS and
DataLA.
D0H
12H
MEM_UOPS_RETIRED.STLB_MIS Retired store uops that miss the STLB.
S_STORES
Supports PEBS and
DataLA.
D0H
21H
MEM_UOPS_RETIRED.LOCK_LOA Retired load uops with locked access.
DS
Supports PEBS and
DataLA.
D0H
41H
MEM_UOPS_RETIRED.SPLIT_LO
ADS
Retired load uops that split across a cacheline
boundary.
Supports PEBS and
DataLA.
D0H
42H
MEM_UOPS_RETIRED.SPLIT_ST
ORES
Retired store uops that split across a cacheline
boundary.
Supports PEBS and
DataLA.
D0H
81H
MEM_UOPS_RETIRED.ALL_LOAD All retired load uops.
S
Supports PEBS and
DataLA.
D0H
82H
MEM_UOPS_RETIRED.ALL_STOR All retired store uops.
ES
Supports PEBS and
DataLA.
D1H
01H
MEM_LOAD_UOPS_RETIRED.L1_ Retired load uops with L1 cache hits as data sources. Supports PEBS and
HIT
DataLA.
D1H
02H
MEM_LOAD_UOPS_RETIRED.L2_ Retired load uops with L2 cache hits as data sources. Supports PEBS and
HIT
DataLA.
D1H
04H
MEM_LOAD_UOPS_RETIRED.L3_ Retired load uops with L3 cache hits as data sources. Supports PEBS and
HIT
DataLA.
Vol. 3B 19-19
PERFORMANCE-MONITORING EVENTS
Table 19-5. Non-Architectural Performance Events of the Processor Core Supported by Broadwell
Microarchitecture (Contd.)
Event
Num.
Umask
Value
D1H
08H
MEM_LOAD_UOPS_RETIRED.L1_ Retired load uops missed L1 cache as data sources.
MISS
Supports PEBS and
DataLA.
D1H
10H
MEM_LOAD_UOPS_RETIRED.L2_ Retired load uops missed L2. Unknown data source
MISS
excluded.
Supports PEBS and
DataLA.
D1H
20H
MEM_LOAD_UOPS_RETIRED.L3_ Retired load uops missed L3. Excludes unknown data Supports PEBS and
MISS
source.
DataLA.
D1H
40H
MEM_LOAD_UOPS_RETIRED.HIT Retired load uops where data sources were load
_LFB
uops missed L1 but hit FB due to preceding miss to
the same cache line with data not ready.
Supports PEBS and
DataLA.
D2H
01H
MEM_LOAD_UOPS_L3_HIT_RETI Retired load uops where data sources were L3 hit
RED.XSNP_MISS
and cross-core snoop missed in on-pkg core cache.
Supports PEBS and
DataLA.
D2H
02H
MEM_LOAD_UOPS_L3_HIT_RETI Retired load uops where data sources were L3 and
RED.XSNP_HIT
cross-core snoop hits in on-pkg core cache.
Supports PEBS and
DataLA.
D2H
04H
MEM_LOAD_UOPS_L3_HIT_RETI Retired load uops where data sources were HitM
RED.XSNP_HITM
responses from shared L3.
Supports PEBS and
DataLA.
D2H
08H
MEM_LOAD_UOPS_L3_HIT_RETI Retired load uops where data sources were hits in
RED.XSNP_NONE
L3 without snoops required.
Supports PEBS and
DataLA.
D3H
01H
MEM_LOAD_UOPS_L3_MISS_RE Retired load uops where data sources missed L3 but Supports PEBS and
TIRED.LOCAL_DRAM
serviced from local dram.
DataLA.
F0H
01H
L2_TRANS.DEMAND_DATA_RD
Event Mask Mnemonic
Description
Comment
Demand data read requests that access L2 cache.
F0H
02H
L2_TRANS.RFO
RFO requests that access L2 cache.
F0H
04H
L2_TRANS.CODE_RD
L2 cache accesses when fetching instructions.
F0H
08H
L2_TRANS.ALL_PF
Any MLC or L3 HW prefetch accessing L2, including
rejects.
F0H
10H
L2_TRANS.L1D_WB
L1D writebacks that access L2 cache.
F0H
20H
L2_TRANS.L2_FILL
L2 fill requests that access L2 cache.
F0H
40H
L2_TRANS.L2_WB
L2 writebacks that access L2 cache.
F0H
80H
L2_TRANS.ALL_REQUESTS
Transactions accessing L2 pipe.
F1H
01H
L2_LINES_IN.I
L2 cache lines in I state filling L2.
Counting does not cover
rejects.
F1H
02H
L2_LINES_IN.S
L2 cache lines in S state filling L2.
Counting does not cover
rejects.
F1H
04H
L2_LINES_IN.E
L2 cache lines in E state filling L2.
Counting does not cover
rejects.
F1H
07H
L2_LINES_IN.ALL
L2 cache lines filling L2.
Counting does not cover
rejects.
F2H
05H
L2_LINES_OUT.DEMAND_CLEAN Clean L2 cache lines evicted by demand.
Table 19-8 lists performance events supporting Intel TSX (see Section 18.11.5) and are applicable to processors
based on Broadwell microarchitecture. Where Broadwell microarchitecture implements TSX-related event semantics that differ from Table 19-8, they are listed in Table 19-6.
19-20 Vol. 3B
PERFORMANCE-MONITORING EVENTS
Table 19-6. Intel® TSX Performance Event Addendum in Processors Based on Broadwell Microarchitecture
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
54H
02H
TX_MEM.ABORT_CAPACITY
Number of times a transactional abort was signaled due
to a data capacity limitation for transactional reads or
writes.
19.4
Comment
PERFORMANCE MONITORING EVENTS FOR THE 4TH GENERATION
INTEL® CORE™ PROCESSORS
4th generation Intel® Core™ processors and Intel Xeon processor E3-1200 v3 product family are based on the
Haswell microarchitecture. They support the architectural performance-monitoring events listed in Table 19-1.
Non-architectural performance-monitoring events in the processor core are listed in Table 19-7. The events in
Table 19-7 apply to processors with CPUID signature of DisplayFamily_DisplayModel encoding with the following
values: 06_3CH, 06_45H and 06_46H. Table 19-8 lists performance events focused on supporting Intel TSX (see
Section 18.11.5). Fixed counters in the core PMU support the architecture events defined in Table 19-2.
Additional information on event specifics (e.g. derivative events using specific IA32_PERFEVTSELx modifiers, limitations, special notes and recommendations) can be found at http://software.intel.com/en-us/forums/softwaretuning-performance-optimization-platform-monitoring.
Table 19-7. Non-Architectural Performance Events in the Processor Core of
4th Generation Intel® Core™ Processors
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
03H
02H
LD_BLOCKS.STORE_FORWARD
Loads blocked by overlapping with store buffer that
cannot be forwarded.
03H
08H
LD_BLOCKS.NO_SR
The number of times that split load operations are
temporarily blocked because all resources for
handling the split accesses are in use.
05H
01H
MISALIGN_MEM_REF.LOADS
Speculative cache-line split load uops dispatched to
L1D.
05H
02H
MISALIGN_MEM_REF.STORES
Speculative cache-line split store-address uops
dispatched to L1D.
07H
01H
LD_BLOCKS_PARTIAL.ADDRESS
_ALIAS
False dependencies in MOB due to partial compare
on address.
08H
01H
DTLB_LOAD_MISSES.MISS_CAUS Misses in all TLB levels that cause a page walk of any
ES_A_WALK
page size.
08H
02H
DTLB_LOAD_MISSES.WALK_COM Completed page walks due to demand load misses
PLETED_4K
that caused 4K page walks in any TLB levels.
08H
04H
DTLB_LOAD_MISSES.WALK_COM Completed page walks due to demand load misses
PLETED_2M_4M
that caused 2M/4M page walks in any TLB levels.
08H
0EH
DTLB_LOAD_MISSES.WALK_COM Completed page walks in any TLB of any page size
PLETED
due to demand load misses.
08H
10H
DTLB_LOAD_MISSES.WALK_DUR Cycle PMH is busy with a walk.
ATION
08H
20H
DTLB_LOAD_MISSES.STLB_HIT_ Load misses that missed DTLB but hit STLB (4K).
4K
08H
40H
DTLB_LOAD_MISSES.STLB_HIT_ Load misses that missed DTLB but hit STLB (2M).
2M
Comment
Vol. 3B 19-21
PERFORMANCE-MONITORING EVENTS
Table 19-7. Non-Architectural Performance Events in the Processor Core of
4th Generation Intel® Core™ Processors (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
08H
60H
DTLB_LOAD_MISSES.STLB_HIT
Number of cache load STLB hits. No page walk.
08H
80H
DTLB_LOAD_MISSES.PDE_CACH DTLB demand load misses with low part of linear-toE_MISS
physical address translation missed.
0DH
03H
INT_MISC.RECOVERY_CYCLES
Cycles waiting to recover after Machine Clears
except JEClear. Set Cmask= 1.
Set Edge to count
occurrences.
0EH
01H
UOPS_ISSUED.ANY
Increments each cycle the # of uops issued by the
RAT to RS. Set Cmask = 1, Inv = 1, Any= 1 to count
stalled cycles of this core.
Set Cmask = 1, Inv = 1to
count stalled cycles.
0EH
10H
UOPS_ISSUED.FLAGS_MERGE
Number of flags-merge uops allocated. Such uops
add delay.
0EH
20H
UOPS_ISSUED.SLOW_LEA
Number of slow LEA or similar uops allocated. Such
uop has 3 sources (for example, 2 sources +
immediate) regardless of whether it is a result of
LEA instruction or not.
0EH
40H
UOPS_ISSUED.SiNGLE_MUL
Number of multiply packed/scalar single precision
uops allocated.
24H
21H
L2_RQSTS.DEMAND_DATA_RD_ Demand data read requests that missed L2, no
MISS
rejects.
24H
41H
L2_RQSTS.DEMAND_DATA_RD_ Demand data read requests that hit L2 cache.
HIT
24H
E1H
L2_RQSTS.ALL_DEMAND_DATA
_RD
Counts any demand and L1 HW prefetch data load
requests to L2.
24H
42H
L2_RQSTS.RFO_HIT
Counts the number of store RFO requests that hit
the L2 cache.
24H
22H
L2_RQSTS.RFO_MISS
Counts the number of store RFO requests that miss
the L2 cache.
24H
E2H
L2_RQSTS.ALL_RFO
Counts all L2 store RFO requests.
24H
44H
L2_RQSTS.CODE_RD_HIT
Number of instruction fetches that hit the L2 cache.
24H
24H
L2_RQSTS.CODE_RD_MISS
Number of instruction fetches that missed the L2
cache.
24H
27H
L2_RQSTS.ALL_DEMAND_MISS
Demand requests that miss L2 cache.
24H
E7H
L2_RQSTS.ALL_DEMAND_REFE
RENCES
Demand requests to L2 cache.
24H
E4H
L2_RQSTS.ALL_CODE_RD
Counts all L2 code requests.
24H
50H
L2_RQSTS.L2_PF_HIT
Counts all L2 HW prefetcher requests that hit L2.
24H
30H
L2_RQSTS.L2_PF_MISS
Counts all L2 HW prefetcher requests that missed
L2.
24H
F8H
L2_RQSTS.ALL_PF
Counts all L2 HW prefetcher requests.
24H
3FH
L2_RQSTS.MISS
All requests that missed L2.
24H
FFH
L2_RQSTS.REFERENCES
All requests to L2 cache.
Not rejected writebacks that hit L2 cache.
Comment
27H
50H
L2_DEMAND_RQSTS.WB_HIT
2EH
4FH
LONGEST_LAT_CACHE.REFEREN This event counts requests originating from the core See Table 19-1.
CE
that reference a cache line in the last level cache.
2EH
41H
LONGEST_LAT_CACHE.MISS
19-22 Vol. 3B
This event counts each cache miss condition for
references to the last level cache.
See Table 19-1.
PERFORMANCE-MONITORING EVENTS
Table 19-7. Non-Architectural Performance Events in the Processor Core of
4th Generation Intel® Core™ Processors (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
3CH
00H
CPU_CLK_UNHALTED.THREAD_
P
Counts the number of thread cycles while the thread See Table 19-1.
is not in a halt state. The thread enters the halt state
when it is running the HLT instruction. The core
frequency may change from time to time due to
power or thermal throttling.
3CH
01H
CPU_CLK_THREAD_UNHALTED.
REF_XCLK
Increments at the frequency of XCLK (100 MHz)
when not halted.
See Table 19-1.
48H
01H
L1D_PEND_MISS.PENDING
Increments the number of outstanding L1D misses
every cycle. Set Cmask = 1 and Edge =1 to count
occurrences.
Counter 2 only.
49H
01H
DTLB_STORE_MISSES.MISS_CAU Miss in all TLB levels causes a page walk of any page
SES_A_WALK
size (4K/2M/4M/1G).
49H
02H
DTLB_STORE_MISSES.WALK_CO Completed page walks due to store misses in one or
MPLETED_4K
more TLB levels of 4K page structure.
49H
04H
DTLB_STORE_MISSES.WALK_CO Completed page walks due to store misses in one or
MPLETED_2M_4M
more TLB levels of 2M/4M page structure.
49H
0EH
DTLB_STORE_MISSES.WALK_CO Completed page walks due to store miss in any TLB
MPLETED
levels of any page size (4K/2M/4M/1G).
49H
10H
DTLB_STORE_MISSES.WALK_DU Cycles PMH is busy with this walk.
RATION
49H
20H
DTLB_STORE_MISSES.STLB_HIT Store misses that missed DTLB but hit STLB (4K).
_4K
49H
40H
DTLB_STORE_MISSES.STLB_HIT Store misses that missed DTLB but hit STLB (2M).
_2M
49H
60H
DTLB_STORE_MISSES.STLB_HIT Store operations that miss the first TLB level but hit
the second and do not cause page walks.
49H
80H
DTLB_STORE_MISSES.PDE_CAC
HE_MISS
DTLB store misses with low part of linear-to-physical
address translation missed.
4CH
01H
LOAD_HIT_PRE.SW_PF
Non-SW-prefetch load dispatches that hit fill buffer
allocated for S/W prefetch.
4CH
02H
LOAD_HIT_PRE.HW_PF
Non-SW-prefetch load dispatches that hit fill buffer
allocated for H/W prefetch.
51H
01H
L1D.REPLACEMENT
Counts the number of lines brought into the L1 data
cache.
58H
04H
MOVE_ELIMINATION.INT_NOT_E Number of integer move elimination candidate uops
LIMINATED
that were not eliminated.
58H
08H
MOVE_ELIMINATION.SIMD_NOT_ Number of SIMD move elimination candidate uops
ELIMINATED
that were not eliminated.
58H
01H
MOVE_ELIMINATION.INT_ELIMIN Number of integer move elimination candidate uops
ATED
that were eliminated.
58H
02H
MOVE_ELIMINATION.SIMD_ELIMI Number of SIMD move elimination candidate uops
NATED
that were eliminated.
5CH
01H
CPL_CYCLES.RING0
Unhalted core cycles when the thread is in ring 0.
5CH
02H
CPL_CYCLES.RING123
Unhalted core cycles when the thread is not in ring 0.
5EH
01H
RS_EVENTS.EMPTY_CYCLES
Cycles the RS is empty for the thread.
Comment
Set Cmask = 1 to count
cycles.
Use Edge to count
transition.
Vol. 3B 19-23
PERFORMANCE-MONITORING EVENTS
Table 19-7. Non-Architectural Performance Events in the Processor Core of
4th Generation Intel® Core™ Processors (Contd.)
Event
Num.
Umask
Value
60H
01H
OFFCORE_REQUESTS_OUTSTAN Offcore outstanding demand data read transactions
DING.DEMAND_DATA_RD
in SQ to uncore. Set Cmask=1 to count cycles.
60H
02H
OFFCORE_REQUESTS_OUTSTAN Offcore outstanding Demand code Read transactions Use only when HTT is
DING.DEMAND_CODE_RD
in SQ to uncore. Set Cmask=1 to count cycles.
off.
60H
04H
OFFCORE_REQUESTS_OUTSTAN Offcore outstanding RFO store transactions in SQ to Use only when HTT is
DING.DEMAND_RFO
uncore. Set Cmask=1 to count cycles.
off.
60H
08H
OFFCORE_REQUESTS_OUTSTAN Offcore outstanding cacheable data read
DING.ALL_DATA_RD
transactions in SQ to uncore. Set Cmask=1 to count
cycles.
63H
01H
LOCK_CYCLES.SPLIT_LOCK_UC_
LOCK_DURATION
Cycles in which the L1D and L2 are locked, due to a
UC lock or split lock.
63H
02H
LOCK_CYCLES.CACHE_LOCK_DU
RATION
Cycles in which the L1D is locked.
79H
02H
IDQ.EMPTY
Counts cycles the IDQ is empty.
79H
04H
IDQ.MITE_UOPS
Increment each cycle # of uops delivered to IDQ from Can combine Umask 04H
MITE path. Set Cmask = 1 to count cycles.
and 20H.
79H
08H
IDQ.DSB_UOPS
Increment each cycle. # of uops delivered to IDQ
from DSB path. Set Cmask = 1 to count cycles.
Can combine Umask 08H
and 10H.
79H
10H
IDQ.MS_DSB_UOPS
Increment each cycle # of uops delivered to IDQ
when MS_busy by DSB. Set Cmask = 1 to count
cycles. Add Edge=1 to count # of delivery.
Can combine Umask 04H,
08H.
79H
20H
IDQ.MS_MITE_UOPS
Increment each cycle # of uops delivered to IDQ
when MS_busy by MITE. Set Cmask = 1 to count
cycles.
Can combine Umask 04H,
08H.
79H
30H
IDQ.MS_UOPS
Increment each cycle # of uops delivered to IDQ from Can combine Umask 04H,
MS by either DSB or MITE. Set Cmask = 1 to count
08H.
cycles.
79H
18H
IDQ.ALL_DSB_CYCLES_ANY_UO
PS
Counts cycles DSB is delivered at least one uops. Set
Cmask = 1.
79H
18H
IDQ.ALL_DSB_CYCLES_4_UOPS
Counts cycles DSB is delivered four uops. Set Cmask
= 4.
79H
24H
IDQ.ALL_MITE_CYCLES_ANY_UO Counts cycles MITE is delivered at least one uop. Set
PS
Cmask = 1.
79H
24H
IDQ.ALL_MITE_CYCLES_4_UOPS Counts cycles MITE is delivered four uops. Set Cmask
= 4.
79H
3CH
IDQ.MITE_ALL_UOPS
# of uops delivered to IDQ from any path.
80H
02H
ICACHE.MISSES
Number of Instruction Cache, Streaming Buffer and
Victim Cache Misses. Includes UC accesses.
85H
01H
ITLB_MISSES.MISS_CAUSES_A_
WALK
Misses in ITLB that causes a page walk of any page
size.
85H
02H
ITLB_MISSES.WALK_COMPLETE
D_4K
Completed page walks due to misses in ITLB 4K page
entries.
85H
04H
ITLB_MISSES.WALK_COMPLETE
D_2M_4M
Completed page walks due to misses in ITLB 2M/4M
page entries.
85H
0EH
ITLB_MISSES.WALK_COMPLETE
D
Completed page walks in ITLB of any page size.
19-24 Vol. 3B
Event Mask Mnemonic
Description
Comment
Use only when HTT is
off.
Use only when HTT is
off.
PERFORMANCE-MONITORING EVENTS
Table 19-7. Non-Architectural Performance Events in the Processor Core of
4th Generation Intel® Core™ Processors (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
85H
10H
ITLB_MISSES.WALK_DURATION
Cycle PMH is busy with a walk.
85H
20H
ITLB_MISSES.STLB_HIT_4K
ITLB misses that hit STLB (4K).
85H
40H
ITLB_MISSES.STLB_HIT_2M
ITLB misses that hit STLB (2M).
85H
60H
ITLB_MISSES.STLB_HIT
ITLB misses that hit STLB. No page walk.
87H
01H
ILD_STALL.LCP
Stalls caused by changing prefix length of the
instruction.
87H
04H
ILD_STALL.IQ_FULL
Stall cycles due to IQ is full.
88H
01H
BR_INST_EXEC.COND
Qualify conditional near branch instructions
executed, but not necessarily retired.
Must combine with
umask 40H, 80H.
88H
02H
BR_INST_EXEC.DIRECT_JMP
Qualify all unconditional near branch instructions
excluding calls and indirect branches.
Must combine with
umask 80H.
88H
04H
BR_INST_EXEC.INDIRECT_JMP_
NON_CALL_RET
Qualify executed indirect near branch instructions
that are not calls nor returns.
Must combine with
umask 80H.
88H
08H
BR_INST_EXEC.RETURN_NEAR
Qualify indirect near branches that have a return
mnemonic.
Must combine with
umask 80H.
88H
10H
BR_INST_EXEC.DIRECT_NEAR_C Qualify unconditional near call branch instructions,
ALL
excluding non call branch, executed.
88H
20H
BR_INST_EXEC.INDIRECT_NEAR Qualify indirect near calls, including both register and Must combine with
_CALL
memory indirect, executed.
umask 80H.
88H
40H
BR_INST_EXEC.NONTAKEN
Qualify non-taken near branches executed.
88H
80H
BR_INST_EXEC.TAKEN
Qualify taken near branches executed. Must combine
with 01H,02H, 04H, 08H, 10H, 20H.
88H
FFH
BR_INST_EXEC.ALL_BRANCHES Counts all near executed branches (not necessarily
retired).
89H
01H
BR_MISP_EXEC.COND
Qualify conditional near branch instructions
mispredicted.
Must combine with
umask 40H, 80H.
89H
04H
BR_MISP_EXEC.INDIRECT_JMP_
NON_CALL_RET
Qualify mispredicted indirect near branch
instructions that are not calls nor returns.
Must combine with
umask 80H.
89H
08H
BR_MISP_EXEC.RETURN_NEAR
Qualify mispredicted indirect near branches that
have a return mnemonic.
Must combine with
umask 80H.
89H
10H
BR_MISP_EXEC.DIRECT_NEAR_C Qualify mispredicted unconditional near call branch
ALL
instructions, excluding non call branch, executed.
Must combine with
umask 80H.
89H
20H
BR_MISP_EXEC.INDIRECT_NEAR Qualify mispredicted indirect near calls, including
_CALL
both register and memory indirect, executed.
Must combine with
umask 80H.
89H
40H
BR_MISP_EXEC.NONTAKEN
Qualify mispredicted non-taken near branches
executed.
Applicable to umask 01H
only.
89H
80H
BR_MISP_EXEC.TAKEN
Qualify mispredicted taken near branches executed.
Must combine with 01H,02H, 04H, 08H, 10H, 20H.
89H
FFH
BR_MISP_EXEC.ALL_BRANCHES Counts all near executed branches (not necessarily
retired).
9CH
01H
IDQ_UOPS_NOT_DELIVERED.CO
RE
Count issue pipeline slots where no uop was
delivered from the front end to the back end when
there is no back-end stall.
Comment
Must combine with
umask 80H.
Applicable to umask 01H
only.
Use Cmask to qualify uop
b/w.
Vol. 3B 19-25
PERFORMANCE-MONITORING EVENTS
Table 19-7. Non-Architectural Performance Events in the Processor Core of
4th Generation Intel® Core™ Processors (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
A1H
01H
UOPS_EXECUTED_PORT.PORT_
0
Cycles which a uop is dispatched on port 0 in this
thread.
Set AnyThread to count
per core.
A1H
02H
UOPS_EXECUTED_PORT.PORT_
1
Cycles which a uop is dispatched on port 1 in this
thread.
Set AnyThread to count
per core.
A1H
04H
UOPS_EXECUTED_PORT.PORT_
2
Cycles which a uop is dispatched on port 2 in this
thread.
Set AnyThread to count
per core.
A1H
08H
UOPS_EXECUTED_PORT.PORT_
3
Cycles which a uop is dispatched on port 3 in this
thread.
Set AnyThread to count
per core.
A1H
10H
UOPS_EXECUTED_PORT.PORT_
4
Cycles which a uop is dispatched on port 4 in this
thread.
Set AnyThread to count
per core.
A1H
20H
UOPS_EXECUTED_PORT.PORT_
5
Cycles which a uop is dispatched on port 5 in this
thread.
Set AnyThread to count
per core.
A1H
40H
UOPS_EXECUTED_PORT.PORT_
6
Cycles which a uop is dispatched on port 6 in this
thread.
Set AnyThread to count
per core.
A1H
80H
UOPS_EXECUTED_PORT.PORT_
7
Cycles which a uop is dispatched on port 7 in this
thread
Set AnyThread to count
per core.
A2H
01H
RESOURCE_STALLS.ANY
Cycles allocation is stalled due to resource related
reason.
A2H
04H
RESOURCE_STALLS.RS
Cycles stalled due to no eligible RS entry available.
A2H
08H
RESOURCE_STALLS.SB
Cycles stalled due to no store buffers available (not
including draining form sync).
A2H
10H
RESOURCE_STALLS.ROB
Cycles stalled due to re-order buffer full.
A3H
01H
CYCLE_ACTIVITY.CYCLES_L2_PE Cycles with pending L2 miss loads. Set Cmask=2 to
NDING
count cycle.
A3H
02H
CYCLE_ACTIVITY.CYCLES_LDM_
PENDING
A3H
05H
CYCLE_ACTIVITY.STALLS_L2_PE Number of loads missed L2.
NDING
Use only when HTT is
off.
A3H
08H
CYCLE_ACTIVITY.CYCLES_L1D_P Cycles with pending L1 data cache miss loads. Set
ENDING
Cmask=8 to count cycle.
PMC2 only.
A3H
0CH
CYCLE_ACTIVITY.STALLS_L1D_P Execution stalls due to L1 data cache miss loads. Set PMC2 only.
ENDING
Cmask=0CH.
A8H
01H
LSD.UOPS
Number of uops delivered by the LSD.
AEH
01H
ITLB.ITLB_FLUSH
Counts the number of ITLB flushes, includes
4k/2M/4M pages.
B0H
01H
OFFCORE_REQUESTS.DEMAND_ Demand data read requests sent to uncore.
DATA_RD
Use only when HTT is
off.
B0H
02H
OFFCORE_REQUESTS.DEMAND_ Demand code read requests sent to uncore.
CODE_RD
Use only when HTT is
off.
B0H
04H
OFFCORE_REQUESTS.DEMAND_ Demand RFO read requests sent to uncore, including Use only when HTT is
RFO
regular RFOs, locks, ItoM.
off.
B0H
08H
OFFCORE_REQUESTS.ALL_DATA Data read requests sent to uncore (demand and
_RD
prefetch).
B1H
02H
UOPS_EXECUTED.CORE
19-26 Vol. 3B
Use only when HTT is
off.
Cycles with pending memory loads. Set Cmask=2 to
count cycle.
Use only when HTT is
off.
Counts total number of uops to be executed per-core Do not need to set ANY.
each cycle.
PERFORMANCE-MONITORING EVENTS
Table 19-7. Non-Architectural Performance Events in the Processor Core of
4th Generation Intel® Core™ Processors (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
B7H
01H
OFF_CORE_RESPONSE_0
See Table 18-48 or Table 18-49.
Requires MSR 01A6H.
BBH
01H
OFF_CORE_RESPONSE_1
See Table 18-48 or Table 18-49.
Requires MSR 01A7H.
BCH
11H
PAGE_WALKER_LOADS.DTLB_L1 Number of DTLB page walker loads that hit in the
L1+FB.
BCH
21H
PAGE_WALKER_LOADS.ITLB_L1
BCH
12H
PAGE_WALKER_LOADS.DTLB_L2 Number of DTLB page walker loads that hit in the L2.
BCH
22H
PAGE_WALKER_LOADS.ITLB_L2
BCH
14H
PAGE_WALKER_LOADS.DTLB_L3 Number of DTLB page walker loads that hit in the L3.
BCH
24H
PAGE_WALKER_LOADS.ITLB_L3
Number of ITLB page walker loads that hit in the L3.
BCH
18H
PAGE_WALKER_LOADS.DTLB_M
EMORY
Number of DTLB page walker loads from memory.
BCH
28H
PAGE_WALKER_LOADS.ITLB_ME Number of ITLB page walker loads from memory.
MORY
BDH
01H
TLB_FLUSH.DTLB_THREAD
DTLB flush attempts of the thread-specific entries.
BDH
20H
TLB_FLUSH.STLB_ANY
Count number of STLB flush attempts.
Number of ITLB page walker loads that hit in the
L1+FB.
Number of ITLB page walker loads that hit in the L2.
C0H
00H
INST_RETIRED.ANY_P
Number of instructions at retirement.
See Table 19-1.
C0H
01H
INST_RETIRED.PREC_DIST
Precise instruction retired event with HW to reduce
effect of PEBS shadow in IP distribution.
PMC1 only.
C1H
08H
OTHER_ASSISTS.AVX_TO_SSE
Number of transitions from AVX-256 to legacy SSE
when penalty applicable.
C1H
10H
OTHER_ASSISTS.SSE_TO_AVX
Number of transitions from SSE to AVX-256 when
penalty applicable.
C1H
40H
OTHER_ASSISTS.ANY_WB_ASSI
ST
Number of microcode assists invoked by HW upon
uop writeback.
C2H
01H
UOPS_RETIRED.ALL
Counts the number of micro-ops retired. Use
Supports PEBS and
Cmask=1 and invert to count active cycles or stalled DataLA; use Any=1 for
cycles.
core granular.
C2H
02H
UOPS_RETIRED.RETIRE_SLOTS
Counts the number of retirement slots used each
cycle.
C3H
02H
MACHINE_CLEARS.MEMORY_OR Counts the number of machine clears due to memory
DERING
order conflicts.
C3H
04H
MACHINE_CLEARS.SMC
Number of self-modifying-code machine clears
detected.
C3H
20H
MACHINE_CLEARS.MASKMOV
Counts the number of executed AVX masked load
operations that refer to an illegal address range with
the mask bits set to 0.
C4H
00H
BR_INST_RETIRED.ALL_BRANC
HES
Branch instructions at retirement.
C4H
01H
BR_INST_RETIRED.CONDITIONA Counts the number of conditional branch instructions Supports PEBS.
L
retired.
C4H
02H
BR_INST_RETIRED.NEAR_CALL
Direct and indirect near call instructions retired.
Supports PEBS.
C4H
04H
BR_INST_RETIRED.ALL_BRANC
HES
Counts the number of branch instructions retired.
Supports PEBS.
Supports PEBS.
See Table 19-1.
Vol. 3B 19-27
PERFORMANCE-MONITORING EVENTS
Table 19-7. Non-Architectural Performance Events in the Processor Core of
4th Generation Intel® Core™ Processors (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
C4H
08H
BR_INST_RETIRED.NEAR_RETU
RN
Counts the number of near return instructions
retired.
Supports PEBS.
C4H
10H
BR_INST_RETIRED.NOT_TAKEN
Counts the number of not taken branch instructions
retired.
C4H
20H
BR_INST_RETIRED.NEAR_TAKE
N
Number of near taken branches retired.
C4H
40H
BR_INST_RETIRED.FAR_BRANC
H
Number of far branches retired.
C5H
00H
BR_MISP_RETIRED.ALL_BRANC
HES
Mispredicted branch instructions at retirement.
C5H
01H
BR_MISP_RETIRED.CONDITIONA Mispredicted conditional branch instructions retired.
L
Supports PEBS.
C5H
04H
BR_MISP_RETIRED.ALL_BRANC
HES
Mispredicted macro branch instructions retired.
Supports PEBS.
C5H
20H
BR_MISP_RETIRED.NEAR_TAKE
N
Number of near branch instructions retired that
were taken but mispredicted.
CAH
02H
FP_ASSIST.X87_OUTPUT
Number of X87 FP assists due to output values.
CAH
04H
FP_ASSIST.X87_INPUT
Number of X87 FP assists due to input values.
CAH
08H
FP_ASSIST.SIMD_OUTPUT
Number of SIMD FP assists due to output values.
CAH
10H
FP_ASSIST.SIMD_INPUT
Number of SIMD FP assists due to input values.
CAH
1EH
FP_ASSIST.ANY
Cycles with any input/output SSE* or FP assists.
CCH
20H
ROB_MISC_EVENTS.LBR_INSER
TS
Count cases of saving new LBR records by hardware.
CDH
01H
MEM_TRANS_RETIRED.LOAD_L
ATENCY
Randomly sampled loads whose latency is above a
Specify threshold in MSR
user defined threshold. A small fraction of the overall 3F6H.
loads are sampled due to randomization.
D0H
11H
MEM_UOPS_RETIRED.STLB_MIS Retired load uops that miss the STLB.
S_LOADS
Supports PEBS and
DataLA.
D0H
12H
MEM_UOPS_RETIRED.STLB_MIS Retired store uops that miss the STLB.
S_STORES
Supports PEBS and
DataLA.
D0H
21H
MEM_UOPS_RETIRED.LOCK_LOA Retired load uops with locked access.
DS
Supports PEBS and
DataLA.
D0H
41H
MEM_UOPS_RETIRED.SPLIT_LO
ADS
Retired load uops that split across a cacheline
boundary.
Supports PEBS and
DataLA.
D0H
42H
MEM_UOPS_RETIRED.SPLIT_ST
ORES
Retired store uops that split across a cacheline
boundary.
Supports PEBS and
DataLA.
D0H
81H
MEM_UOPS_RETIRED.ALL_LOAD All retired load uops.
S
Supports PEBS and
DataLA.
D0H
82H
MEM_UOPS_RETIRED.ALL_STOR All retired store uops.
ES
Supports PEBS and
DataLA.
D1H
01H
MEM_LOAD_UOPS_RETIRED.L1_ Retired load uops with L1 cache hits as data sources. Supports PEBS and
HIT
DataLA.
D1H
02H
MEM_LOAD_UOPS_RETIRED.L2_ Retired load uops with L2 cache hits as data sources. Supports PEBS and
HIT
DataLA.
19-28 Vol. 3B
Supports PEBS.
See Table 19-1.
PERFORMANCE-MONITORING EVENTS
Table 19-7. Non-Architectural Performance Events in the Processor Core of
4th Generation Intel® Core™ Processors (Contd.)
Event
Num.
Umask
Value
D1H
04H
MEM_LOAD_UOPS_RETIRED.L3_ Retired load uops with L3 cache hits as data sources. Supports PEBS and
HIT
DataLA.
D1H
08H
MEM_LOAD_UOPS_RETIRED.L1_ Retired load uops missed L1 cache as data sources.
MISS
Supports PEBS and
DataLA.
D1H
10H
MEM_LOAD_UOPS_RETIRED.L2_ Retired load uops missed L2. Unknown data source
MISS
excluded.
Supports PEBS and
DataLA.
D1H
20H
MEM_LOAD_UOPS_RETIRED.L3_ Retired load uops missed L3. Excludes unknown data Supports PEBS and
MISS
source .
DataLA.
D1H
40H
MEM_LOAD_UOPS_RETIRED.HIT Retired load uops which data sources were load uops Supports PEBS and
DataLA.
_LFB
missed L1 but hit FB due to preceding miss to the
same cache line with data not ready.
D2H
01H
MEM_LOAD_UOPS_L3_HIT_RETI Retired load uops which data sources were L3 hit
RED.XSNP_MISS
and cross-core snoop missed in on-pkg core cache.
Supports PEBS and
DataLA.
D2H
02H
MEM_LOAD_UOPS_L3_HIT_RETI Retired load uops which data sources were L3 and
RED.XSNP_HIT
cross-core snoop hits in on-pkg core cache.
Supports PEBS and
DataLA.
D2H
04H
MEM_LOAD_UOPS_L3_HIT_RETI Retired load uops which data sources were HitM
RED.XSNP_HITM
responses from shared L3.
Supports PEBS and
DataLA.
D2H
08H
MEM_LOAD_UOPS_L3_HIT_RETI Retired load uops which data sources were hits in L3 Supports PEBS and
RED.XSNP_NONE
without snoops required.
DataLA.
D3H
01H
MEM_LOAD_UOPS_L3_MISS_RE Retired load uops which data sources missed L3 but
TIRED.LOCAL_DRAM
serviced from local dram.
E6H
1FH
BACLEARS.ANY
Number of front end re-steers due to BPU
misprediction.
F0H
01H
L2_TRANS.DEMAND_DATA_RD
Demand data read requests that access L2 cache.
F0H
02H
L2_TRANS.RFO
RFO requests that access L2 cache.
F0H
04H
L2_TRANS.CODE_RD
L2 cache accesses when fetching instructions.
F0H
08H
L2_TRANS.ALL_PF
Any MLC or L3 HW prefetch accessing L2, including
rejects.
F0H
10H
L2_TRANS.L1D_WB
L1D writebacks that access L2 cache.
F0H
20H
L2_TRANS.L2_FILL
L2 fill requests that access L2 cache.
F0H
40H
L2_TRANS.L2_WB
L2 writebacks that access L2 cache.
F0H
80H
L2_TRANS.ALL_REQUESTS
Transactions accessing L2 pipe.
F1H
01H
L2_LINES_IN.I
L2 cache lines in I state filling L2.
Counting does not cover
rejects.
F1H
02H
L2_LINES_IN.S
L2 cache lines in S state filling L2.
Counting does not cover
rejects.
F1H
04H
L2_LINES_IN.E
L2 cache lines in E state filling L2.
Counting does not cover
rejects.
F1H
07H
L2_LINES_IN.ALL
L2 cache lines filling L2.
Counting does not cover
rejects.
Event Mask Mnemonic
Description
F2H
05H
L2_LINES_OUT.DEMAND_CLEAN Clean L2 cache lines evicted by demand.
F2H
06H
L2_LINES_OUT.DEMAND_DIRTY
Comment
Supports PEBS and
DataLA.
Dirty L2 cache lines evicted by demand.
Vol. 3B 19-29
PERFORMANCE-MONITORING EVENTS
Table 19-8. Intel TSX Performance Events in Processors Based on Haswell Microarchitecture
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
54H
01H
TX_MEM.ABORT_CONFLICT
Number of times a transactional abort was signaled due
to a data conflict on a transactionally accessed address.
54H
02H
TX_MEM.ABORT_CAPACITY_W Number of times a transactional abort was signaled due
RITE
to a data capacity limitation for transactional writes.
54H
04H
TX_MEM.ABORT_HLE_STORE_ Number of times a HLE transactional region aborted due
TO_ELIDED_LOCK
to a non XRELEASE prefixed instruction writing to an
elided lock in the elision buffer.
54H
08H
TX_MEM.ABORT_HLE_ELISION Number of times an HLE transactional execution aborted
_BUFFER_NOT_EMPTY
due to NoAllocatedElisionBuffer being non-zero.
54H
10H
TX_MEM.ABORT_HLE_ELISION Number of times an HLE transactional execution aborted
_BUFFER_MISMATCH
due to XRELEASE lock not satisfying the address and
value requirements in the elision buffer.
54H
20H
TX_MEM.ABORT_HLE_ELISION Number of times an HLE transactional execution aborted
_BUFFER_UNSUPPORTED_ALI due to an unsupported read alignment from the elision
GNMENT
buffer.
54H
40H
TX_MEM.HLE_ELISION_BUFFE
R_FULL
Number of times HLE lock could not be elided due to
ElisionBufferAvailable being zero.
5DH
01H
TX_EXEC.MISC1
Counts the number of times a class of instructions that
may cause a transactional abort was executed. Since this
is the count of execution, it may not always cause a
transactional abort.
5DH
02H
TX_EXEC.MISC2
Counts the number of times a class of instructions (for
example, vzeroupper) that may cause a transactional
abort was executed inside a transactional region.
5DH
04H
TX_EXEC.MISC3
Counts the number of times an instruction execution
caused the transactional nest count supported to be
exceeded.
5DH
08H
TX_EXEC.MISC4
Counts the number of times an XBEGIN instruction was
executed inside an HLE transactional region.
5DH
10H
TX_EXEC.MISC5
Counts the number of times an instruction with HLEXACQUIRE semantic was executed inside an RTM
transactional region.
19-30 Vol. 3B
Comment
PERFORMANCE-MONITORING EVENTS
Table 19-8. Intel TSX Performance Events in Processors Based on Haswell Microarchitecture
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
C8H
01H
HLE_RETIRED.START
Number of times an HLE execution started.
IF HLE is supported.
C8H
02H
HLE_RETIRED.COMMIT
Number of times an HLE execution successfully
committed.
C8H
04H
HLE_RETIRED.ABORTED
Number of times an HLE execution aborted due to any
reasons (multiple categories may count as one). Supports
PEBS.
C8H
08H
HLE_RETIRED.ABORTED_MEM
Number of times an HLE execution aborted due to
various memory events (for example, read/write
capacity and conflicts).
C8H
10H
HLE_RETIRED.ABORTED_TIME
R
Number of times an HLE execution aborted due to
uncommon conditions.
C8H
20H
HLE_RETIRED.ABORTED_UNFR Number of times an HLE execution aborted due to HLEIENDLY
unfriendly instructions.
C8H
40H
HLE_RETIRED.ABORTED_MEM
TYPE
C8H
80H
HLE_RETIRED.ABORTED_EVEN Number of times an HLE execution aborted due to none
TS
of the previous 4 categories (for example, interrupts).
C9H
01H
RTM_RETIRED.START
Number of times an RTM execution started.
C9H
02H
RTM_RETIRED.COMMIT
Number of times an RTM execution successfully
committed.
C9H
04H
RTM_RETIRED.ABORTED
Number of times an RTM execution aborted due to any
reasons (multiple categories may count as one). Supports
PEBS.
C9H
08H
RTM_RETIRED.ABORTED_MEM Number of times an RTM execution aborted due to
various memory events (for example, read/write
capacity and conflicts).
C9H
10H
RTM_RETIRED.ABORTED_TIME Number of times an RTM execution aborted due to
R
uncommon conditions.
C9H
20H
RTM_RETIRED.ABORTED_UNF
RIENDLY
C9H
40H
RTM_RETIRED.ABORTED_MEM Number of times an RTM execution aborted due to
TYPE
incompatible memory type.
C9H
80H
RTM_RETIRED.ABORTED_EVE
NTS
Number of times an HLE execution aborted due to
incompatible memory type.
IF RTM is supported.
IF RTM is supported.
Number of times an RTM execution aborted due to HLEunfriendly instructions.
Number of times an RTM execution aborted due to none
of the previous 4 categories (for example, interrupt).
Non-architectural performance monitoring events that are located in the uncore sub-system are implementation
specific between different platforms using processors based on Haswell microarchitecture and with different
DisplayFamily_DisplayModel signatures. Processors with CPUID signature of DisplayFamily_DisplayModel 06_3CH
and 06_45H support performance events listed in Table 19-9.
Vol. 3B 19-31
PERFORMANCE-MONITORING EVENTS
Table 19-9. Non-Architectural Uncore Performance Events in the 4th Generation Intel® Core™ Processors
Event
Num.1
Umask
Value
22H
01H
UNC_CBO_XSNP_RESPONSE.M A snoop misses in some processor core.
ISS
22H
02H
UNC_CBO_XSNP_RESPONSE.I
NVAL
22H
04H
UNC_CBO_XSNP_RESPONSE.H A snoop hits a non-modified line in some processor
IT
core.
22H
08H
UNC_CBO_XSNP_RESPONSE.H A snoop hits a modified line in some processor core.
ITM
22H
10H
UNC_CBO_XSNP_RESPONSE.I
NVAL_M
A snoop invalidates a modified line in some processor
core.
22H
20H
UNC_CBO_XSNP_RESPONSE.E
XTERNAL_FILTER
Filter on cross-core snoops initiated by this Cbox due
to external snoop request.
22H
40H
UNC_CBO_XSNP_RESPONSE.X Filter on cross-core snoops initiated by this Cbox due
CORE_FILTER
to processor core memory request.
22H
80H
UNC_CBO_XSNP_RESPONSE.E
VICTION_FILTER
Filter on cross-core snoops initiated by this Cbox due
to L3 eviction.
34H
01H
UNC_CBO_CACHE_LOOKUP.M
L3 lookup request that access cache and found line in
M-state.
34H
06H
UNC_CBO_CACHE_LOOKUP.ES
34H
08H
UNC_CBO_CACHE_LOOKUP.I
L3 lookup request that access cache and found line in Istate.
34H
10H
UNC_CBO_CACHE_LOOKUP.RE
AD_FILTER
Filter on processor core initiated cacheable read
requests. Must combine with at least one of 01H, 02H,
04H, 08H.
34H
20H
UNC_CBO_CACHE_LOOKUP.WR Filter on processor core initiated cacheable write
ITE_FILTER
requests. Must combine with at least one of 01H, 02H,
04H, 08H.
34H
40H
UNC_CBO_CACHE_LOOKUP.EX
TSNP_FILTER
34H
80H
UNC_CBO_CACHE_LOOKUP.AN Filter on any IRQ or IPQ initiated requests including
Y_REQUEST_FILTER
uncacheable, non-coherent requests. Must combine
with at least one of 01H, 02H, 04H, 08H.
80H
01H
UNC_ARB_TRK_OCCUPANCY.A Counts cycles weighted by the number of requests
Counter 0 only.
LL
waiting for data returning from the memory controller.
Accounts for coherent and non-coherent requests
initiated by IA cores, processor graphic units, or L3.
81H
01H
UNC_ARB_TRK_REQUEST.ALL
Counts the number of coherent and in-coherent
requests initiated by IA cores, processor graphic units,
or L3.
81H
20H
UNC_ARB_TRK_REQUEST.WRI
TES
Counts the number of allocated write entries, include
full, partial, and L3 evictions.
81H
80H
UNC_ARB_TRK_REQUEST.EVIC Counts the number of L3 evictions allocated.
TIONS
19-32 Vol. 3B
Event Mask Mnemonic
Description
A snoop invalidates a non-modified line in some
processor core.
Comment
Must combine with
one of the umask
values of 20H, 40H,
80H.
Must combine with at
least one of 01H, 02H,
04H, 08H, 10H.
Must combine with
one of the umask
L3 lookup request that access cache and found line in E values of 10H, 20H,
40H, 80H.
or S state.
Filter on external snoop requests. Must combine with
at least one of 01H, 02H, 04H, 08H.
PERFORMANCE-MONITORING EVENTS
Table 19-9. Non-Architectural Uncore Performance Events in the 4th Generation Intel® Core™ Processors (Contd.)
Event
Num.1
Umask
Value
Event Mask Mnemonic
Description
Comment
83H
01H
UNC_ARB_COH_TRK_OCCUPA
NCY.ALL
Cycles weighted by number of requests pending in
Coherency Tracker.
Counter 0 only.
84H
01H
UNC_ARB_COH_TRK_REQUES
T.ALL
Number of requests allocated in Coherency Tracker.
NOTES:
1. The uncore events must be programmed using MSRs located in specific performance monitoring units in the uncore. UNC_CBO*
events are supported using MSR_UNC_CBO* MSRs; UNC_ARB* events are supported using MSR_UNC_ARB*MSRs.
19.4.1
Performance Monitoring Events in the Processor Core of Intel Xeon Processor E5 v3
Family
Non-architectural performance monitoring events in the processor core that are applicable only to Intel Xeon
processor E5 v3 family based on the Haswell-E microarchitecture, with CPUID signature of
DisplayFamily_DisplayModel 06_3FH, are listed in Table 19-10. The performance events listed in Table 19-7 and
Table 19-8 also apply Intel Xeon processor E5 v3 family, except that the OFF_CORE_RESPONSE_x event listed in
Table 19-7 should reference Table 18-50.
Uncore performance monitoring events for Intel Xeon Processor E5 v3 families are described in “Intel® Xeon®
Processor E5 v3 Uncore Performance Monitoring Programming Reference Manual”.
Table 19-10. Non-Architectural Performance Events Applicable only to the Processor Core of
Intel® Xeon® Processor E5 v3 Family
Event
Num.
Umask
Value
D3H
04H
MEM_LOAD_UOPS_L3_MISS_RE Retired load uops whose data sources was remote
TIRED.REMOTE_DRAM
DRAM (snoop not needed, Snoop Miss).
Supports PEBS.
D3H
10H
MEM_LOAD_UOPS_L3_MISS_RE Retired load uops whose data sources was remote
TIRED.REMOTE_HITM
cache HITM.
Supports PEBS.
D3H
20H
MEM_LOAD_UOPS_L3_MISS_RE Retired load uops whose data sources was forwards
TIRED.REMOTE_FWD
from a remote cache.
Supports PEBS.
19.5
Event Mask Mnemonic
Description
Comment
PERFORMANCE MONITORING EVENTS FOR 3RD GENERATION
INTEL® CORE™ PROCESSORS
3rd generation Intel® Core™ processors and Intel Xeon processor E3-1200 v2 product family are based on Intel
microarchitecture code name Ivy Bridge. They support architectural performance-monitoring events listed in Table
19-1. Non-architectural performance-monitoring events in the processor core are listed in Table 19-11. The events
in Table 19-11 apply to processors with CPUID signature of DisplayFamily_DisplayModel encoding with the
following values: 06_3AH. Fixed counters in the core PMU support the architecture events defined in Table 19-22.
Additional information on event specifics (e.g. derivative events using specific IA32_PERFEVTSELx modifiers, limitations, special notes and recommendations) can be found at http://software.intel.com/en-us/forums/softwaretuning-performance-optimization-platform-monitoring.
Vol. 3B 19-33
PERFORMANCE-MONITORING EVENTS
Table 19-11. Non-Architectural Performance Events In the Processor Core of
3rd Generation Intel® Core™ i7, i5, i3 Processors
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
03H
02H
LD_BLOCKS.STORE_FORWARD
Loads blocked by overlapping with store buffer that
cannot be forwarded.
03H
08H
LD_BLOCKS.NO_SR
The number of times that split load operations are
temporarily blocked because all resources for
handling the split accesses are in use.
05H
01H
MISALIGN_MEM_REF.LOADS
Speculative cache-line split load uops dispatched to
L1D.
05H
02H
MISALIGN_MEM_REF.STORES
Speculative cache-line split Store-address uops
dispatched to L1D.
07H
01H
LD_BLOCKS_PARTIAL.ADDRESS_
ALIAS
False dependencies in MOB due to partial compare
on address.
08H
81H
DTLB_LOAD_MISSES.MISS_CAUSE Misses in all TLB levels that cause a page walk of
S_A_WALK
any page size from demand loads.
08H
82H
DTLB_LOAD_MISSES.WALK_COM
PLETED
Misses in all TLB levels that caused page walk
completed of any size by demand loads.
08H
84H
DTLB_LOAD_MISSES.WALK_DUR
ATION
Cycle PMH is busy with a walk due to demand loads.
08H
88H
DTLB_LOAD_MISSES.LARGE_PAG Page walk for a large page completed for Demand
E_WALK_DURATION
load.
0EH
01H
UOPS_ISSUED.ANY
Increments each cycle the # of Uops issued by the
RAT to RS. Set Cmask = 1, Inv = 1, Any= 1to count
stalled cycles of this core.
0EH
10H
UOPS_ISSUED.FLAGS_MERGE
Number of flags-merge uops allocated. Such uops
adds delay.
0EH
20H
UOPS_ISSUED.SLOW_LEA
Number of slow LEA or similar uops allocated. Such
uop has 3 sources (e.g. 2 sources + immediate)
regardless if as a result of LEA instruction or not.
0EH
40H
UOPS_ISSUED.SiNGLE_MUL
Number of multiply packed/scalar single precision
uops allocated.
10H
01H
FP_COMP_OPS_EXE.X87
Counts number of X87 uops executed.
10H
10H
FP_COMP_OPS_EXE.SSE_FP_PAC Counts number of SSE* or AVX-128 double
KED_DOUBLE
precision FP packed uops executed.
10H
20H
FP_COMP_OPS_EXE.SSE_FP_SCA Counts number of SSE* or AVX-128 single precision
LAR_SINGLE
FP scalar uops executed.
10H
40H
FP_COMP_OPS_EXE.SSE_PACKED Counts number of SSE* or AVX-128 single precision
SINGLE
FP packed uops executed.
10H
80H
FP_COMP_OPS_EXE.SSE_SCALAR Counts number of SSE* or AVX-128 double
_DOUBLE
precision FP scalar uops executed.
11H
01H
SIMD_FP_256.PACKED_SINGLE
Counts 256-bit packed single-precision floatingpoint instructions.
11H
02H
SIMD_FP_256.PACKED_DOUBLE
Counts 256-bit packed double-precision floatingpoint instructions.
14H
01H
ARITH.FPU_DIV_ACTIVE
Cycles that the divider is active, includes INT and FP.
Set 'edge =1, cmask=1' to count the number of
divides.
19-34 Vol. 3B
Comment
Set Cmask = 1, Inv = 1to
count stalled cycles.
PERFORMANCE-MONITORING EVENTS
Table 19-11. Non-Architectural Performance Events In the Processor Core of
3rd Generation Intel® Core™ i7, i5, i3 Processors (Contd.)
Event
Num.
Umask
Value
24H
01H
L2_RQSTS.DEMAND_DATA_RD_H Demand Data Read requests that hit L2 cache.
IT
24H
03H
L2_RQSTS.ALL_DEMAND_DATA_
RD
Counts any demand and L1 HW prefetch data load
requests to L2.
24H
04H
L2_RQSTS.RFO_HITS
Counts the number of store RFO requests that hit
the L2 cache.
24H
08H
L2_RQSTS.RFO_MISS
Counts the number of store RFO requests that miss
the L2 cache.
Event Mask Mnemonic
Description
24H
0CH
L2_RQSTS.ALL_RFO
Counts all L2 store RFO requests.
24H
10H
L2_RQSTS.CODE_RD_HIT
Number of instruction fetches that hit the L2 cache.
24H
20H
L2_RQSTS.CODE_RD_MISS
Number of instruction fetches that missed the L2
cache.
24H
30H
L2_RQSTS.ALL_CODE_RD
Counts all L2 code requests.
24H
40H
L2_RQSTS.PF_HIT
Counts all L2 HW prefetcher requests that hit L2.
24H
80H
L2_RQSTS.PF_MISS
Counts all L2 HW prefetcher requests that missed
L2.
Comment
24H
C0H
L2_RQSTS.ALL_PF
Counts all L2 HW prefetcher requests.
27H
01H
L2_STORE_LOCK_RQSTS.MISS
RFOs that miss cache lines.
27H
08H
L2_STORE_LOCK_RQSTS.HIT_M
RFOs that hit cache lines in M state.
27H
0FH
L2_STORE_LOCK_RQSTS.ALL
RFOs that access cache lines in any state.
28H
01H
L2_L1D_WB_RQSTS.MISS
Not rejected writebacks that missed LLC.
28H
04H
L2_L1D_WB_RQSTS.HIT_E
Not rejected writebacks from L1D to L2 cache lines
in E state.
28H
08H
L2_L1D_WB_RQSTS.HIT_M
Not rejected writebacks from L1D to L2 cache lines
in M state.
28H
0FH
L2_L1D_WB_RQSTS.ALL
Not rejected writebacks from L1D to L2 cache lines
in any state.
2EH
4FH
LONGEST_LAT_CACHE.REFERENC This event counts requests originating from the
E
core that reference a cache line in the last level
cache.
See Table 19-1
2EH
41H
LONGEST_LAT_CACHE.MISS
This event counts each cache miss condition for
references to the last level cache.
See Table 19-1
3CH
00H
CPU_CLK_UNHALTED.THREAD_P
Counts the number of thread cycles while the
thread is not in a halt state. The thread enters the
halt state when it is running the HLT instruction.
The core frequency may change from time to time
due to power or thermal throttling.
See Table 19-1.
3CH
01H
CPU_CLK_THREAD_UNHALTED.R Increments at the frequency of XCLK (100 MHz)
EF_XCLK
when not halted.
See Table 19-1.
48H
01H
L1D_PEND_MISS.PENDING
PMC2 only;
49H
01H
Increments the number of outstanding L1D misses
every cycle. Set Cmask = 1 and Edge =1 to count
occurrences.
Set Cmask = 1 to count
cycles.
DTLB_STORE_MISSES.MISS_CAUS Miss in all TLB levels causes an page walk of any
ES_A_WALK
page size (4K/2M/4M/1G).
Vol. 3B 19-35
PERFORMANCE-MONITORING EVENTS
Table 19-11. Non-Architectural Performance Events In the Processor Core of
3rd Generation Intel® Core™ i7, i5, i3 Processors (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
49H
02H
DTLB_STORE_MISSES.WALK_CO
MPLETED
Miss in all TLB levels causes a page walk that
completes of any page size (4K/2M/4M/1G).
49H
04H
DTLB_STORE_MISSES.WALK_DUR Cycles PMH is busy with this walk.
ATION
49H
10H
DTLB_STORE_MISSES.STLB_HIT
Store operations that miss the first TLB level but hit
the second and do not cause page walks.
4CH
01H
LOAD_HIT_PRE.SW_PF
Non-SW-prefetch load dispatches that hit fill buffer
allocated for S/W prefetch.
4CH
02H
LOAD_HIT_PRE.HW_PF
Non-SW-prefetch load dispatches that hit fill buffer
allocated for H/W prefetch.
51H
01H
L1D.REPLACEMENT
Counts the number of lines brought into the L1 data
cache.
58H
04H
MOVE_ELIMINATION.INT_NOT_EL Number of integer Move Elimination candidate uops
IMINATED
that were not eliminated.
58H
08H
MOVE_ELIMINATION.SIMD_NOT_E Number of SIMD Move Elimination candidate uops
LIMINATED
that were not eliminated.
58H
01H
MOVE_ELIMINATION.INT_ELIMINA Number of integer Move Elimination candidate uops
TED
that were eliminated.
58H
02H
MOVE_ELIMINATION.SIMD_ELIMIN Number of SIMD Move Elimination candidate uops
ATED
that were eliminated.
5CH
01H
CPL_CYCLES.RING0
Unhalted core cycles when the thread is in ring 0.
5CH
02H
CPL_CYCLES.RING123
Unhalted core cycles when the thread is not in ring
0.
5EH
01H
RS_EVENTS.EMPTY_CYCLES
Cycles the RS is empty for the thread.
5FH
04H
DTLB_LOAD_MISSES.STLB_HIT
Counts load operations that missed 1st level DTLB
but hit the 2nd level.
60H
01H
OFFCORE_REQUESTS_OUTSTAN
DING.DEMAND_DATA_RD
Offcore outstanding Demand Data Read
transactions in SQ to uncore. Set Cmask=1 to count
cycles.
60H
02H
OFFCORE_REQUESTS_OUTSTAN
DING.DEMAND_CODE_RD
Offcore outstanding Demand Code Read
transactions in SQ to uncore. Set Cmask=1 to count
cycles.
60H
04H
OFFCORE_REQUESTS_OUTSTAN
DING.DEMAND_RFO
Offcore outstanding RFO store transactions in SQ to
uncore. Set Cmask=1 to count cycles.
60H
08H
OFFCORE_REQUESTS_OUTSTAN
DING.ALL_DATA_RD
Offcore outstanding cacheable data read
transactions in SQ to uncore. Set Cmask=1 to count
cycles.
63H
01H
LOCK_CYCLES.SPLIT_LOCK_UC_L
OCK_DURATION
Cycles in which the L1D and L2 are locked, due to a
UC lock or split lock.
63H
02H
LOCK_CYCLES.CACHE_LOCK_DUR Cycles in which the L1D is locked.
ATION
79H
02H
IDQ.EMPTY
Counts cycles the IDQ is empty.
79H
04H
IDQ.MITE_UOPS
Increment each cycle # of uops delivered to IDQ
from MITE path. Set Cmask = 1 to count cycles.
19-36 Vol. 3B
Comment
Use Edge to count
transition.
Can combine Umask 04H
and 20H.
PERFORMANCE-MONITORING EVENTS
Table 19-11. Non-Architectural Performance Events In the Processor Core of
3rd Generation Intel® Core™ i7, i5, i3 Processors (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
79H
08H
IDQ.DSB_UOPS
Increment each cycle. # of uops delivered to IDQ
from DSB path. Set Cmask = 1 to count cycles.
Can combine Umask 08H
and 10H.
79H
10H
IDQ.MS_DSB_UOPS
Increment each cycle # of uops delivered to IDQ
when MS_busy by DSB. Set Cmask = 1 to count
cycles. Add Edge=1 to count # of delivery.
Can combine Umask 04H,
08H.
79H
20H
IDQ.MS_MITE_UOPS
Increment each cycle # of uops delivered to IDQ
when MS_busy by MITE. Set Cmask = 1 to count
cycles.
Can combine Umask 04H,
08H.
79H
30H
IDQ.MS_UOPS
Increment each cycle # of uops delivered to IDQ
from MS by either DSB or MITE. Set Cmask = 1 to
count cycles.
Can combine Umask 04H,
08H.
79H
18H
IDQ.ALL_DSB_CYCLES_ANY_UOP
S
Counts cycles DSB is delivered at least one uops.
Set Cmask = 1.
79H
18H
IDQ.ALL_DSB_CYCLES_4_UOPS
Counts cycles DSB is delivered four uops. Set Cmask
= 4.
79H
24H
IDQ.ALL_MITE_CYCLES_ANY_UOP Counts cycles MITE is delivered at least one uops.
S
Set Cmask = 1.
79H
24H
IDQ.ALL_MITE_CYCLES_4_UOPS
Counts cycles MITE is delivered four uops. Set
Cmask = 4.
79H
3CH
IDQ.MITE_ALL_UOPS
# of uops delivered to IDQ from any path.
80H
04H
ICACHE.IFETCH_STALL
Cycles where a code-fetch stalled due to L1
instruction-cache miss or an iTLB miss.
80H
02H
ICACHE.MISSES
Number of Instruction Cache, Streaming Buffer and
Victim Cache Misses. Includes UC accesses.
85H
01H
ITLB_MISSES.MISS_CAUSES_A_W Misses in all ITLB levels that cause page walks.
ALK
85H
02H
ITLB_MISSES.WALK_COMPLETED
85H
04H
ITLB_MISSES.WALK_DURATION
Cycle PMH is busy with a walk.
85H
10H
ITLB_MISSES.STLB_HIT
Number of cache load STLB hits. No page walk.
87H
01H
ILD_STALL.LCP
Stalls caused by changing prefix length of the
instruction.
87H
04H
ILD_STALL.IQ_FULL
Stall cycles due to IQ is full.
88H
01H
BR_INST_EXEC.COND
Qualify conditional near branch instructions
executed, but not necessarily retired.
Must combine with
umask 40H, 80H.
88H
02H
BR_INST_EXEC.DIRECT_JMP
Qualify all unconditional near branch instructions
excluding calls and indirect branches.
Must combine with
umask 80H.
88H
04H
BR_INST_EXEC.INDIRECT_JMP_N
ON_CALL_RET
Qualify executed indirect near branch instructions
that are not calls nor returns.
Must combine with
umask 80H.
88H
08H
BR_INST_EXEC.RETURN_NEAR
Qualify indirect near branches that have a return
mnemonic.
Must combine with
umask 80H.
88H
10H
BR_INST_EXEC.DIRECT_NEAR_C
ALL
Qualify unconditional near call branch instructions,
excluding non call branch, executed.
Must combine with
umask 80H.
88H
20H
BR_INST_EXEC.INDIRECT_NEAR_ Qualify indirect near calls, including both register
CALL
and memory indirect, executed.
Misses in all ITLB levels that cause completed page
walks.
Must combine with
umask 80H.
Vol. 3B 19-37
PERFORMANCE-MONITORING EVENTS
Table 19-11. Non-Architectural Performance Events In the Processor Core of
3rd Generation Intel® Core™ i7, i5, i3 Processors (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
88H
40H
BR_INST_EXEC.NONTAKEN
Qualify non-taken near branches executed.
Applicable to umask 01H
only.
88H
80H
BR_INST_EXEC.TAKEN
Qualify taken near branches executed. Must
combine with 01H,02H, 04H, 08H, 10H, 20H.
88H
FFH
BR_INST_EXEC.ALL_BRANCHES
Counts all near executed branches (not necessarily
retired).
89H
01H
BR_MISP_EXEC.COND
Qualify conditional near branch instructions
mispredicted.
Must combine with
umask 40H, 80H.
89H
04H
BR_MISP_EXEC.INDIRECT_JMP_N
ON_CALL_RET
Qualify mispredicted indirect near branch
instructions that are not calls nor returns.
Must combine with
umask 80H.
89H
08H
BR_MISP_EXEC.RETURN_NEAR
Qualify mispredicted indirect near branches that
have a return mnemonic.
Must combine with
umask 80H.
89H
10H
BR_MISP_EXEC.DIRECT_NEAR_C
ALL
Qualify mispredicted unconditional near call branch
instructions, excluding non call branch, executed.
Must combine with
umask 80H.
89H
20H
BR_MISP_EXEC.INDIRECT_NEAR_ Qualify mispredicted indirect near calls, including
CALL
both register and memory indirect, executed.
Must combine with
umask 80H.
89H
40H
BR_MISP_EXEC.NONTAKEN
Qualify mispredicted non-taken near branches
executed.
Applicable to umask 01H
only.
89H
80H
BR_MISP_EXEC.TAKEN
Qualify mispredicted taken near branches executed.
Must combine with 01H,02H, 04H, 08H, 10H, 20H.
89H
FFH
BR_MISP_EXEC.ALL_BRANCHES
Counts all near executed branches (not necessarily
retired).
9CH
01H
IDQ_UOPS_NOT_DELIVERED.COR Count issue pipeline slots where no uop was
E
delivered from the front end to the back end when
there is no back-end stall.
A1H
01H
UOPS_DISPATCHED_PORT.PORT_ Cycles which a Uop is dispatched on port 0.
0
A1H
02H
UOPS_DISPATCHED_PORT.PORT_ Cycles which a Uop is dispatched on port 1.
1
A1H
0CH
UOPS_DISPATCHED_PORT.PORT_ Cycles which a Uop is dispatched on port 2.
2
A1H
30H
UOPS_DISPATCHED_PORT.PORT_ Cycles which a Uop is dispatched on port 3.
3
A1H
40H
UOPS_DISPATCHED_PORT.PORT_ Cycles which a Uop is dispatched on port 4.
4
A1H
80H
UOPS_DISPATCHED_PORT.PORT_ Cycles which a Uop is dispatched on port 5.
5
A2H
01H
RESOURCE_STALLS.ANY
Cycles Allocation is stalled due to Resource Related
reason.
A2H
04H
RESOURCE_STALLS.RS
Cycles stalled due to no eligible RS entry available.
A2H
08H
RESOURCE_STALLS.SB
Cycles stalled due to no store buffers available (not
including draining form sync).
A2H
10H
RESOURCE_STALLS.ROB
Cycles stalled due to re-order buffer full.
A3H
01H
CYCLE_ACTIVITY.CYCLES_L2_PEN Cycles with pending L2 miss loads. Set AnyThread
DING
to count per core.
19-38 Vol. 3B
Use Cmask to qualify uop
b/w.
PERFORMANCE-MONITORING EVENTS
Table 19-11. Non-Architectural Performance Events In the Processor Core of
3rd Generation Intel® Core™ i7, i5, i3 Processors (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
A3H
02H
CYCLE_ACTIVITY.CYCLES_LDM_P
ENDING
Cycles with pending memory loads. Set AnyThread
to count per core.
Restricted to counters 03 when HTT is disabled.
A3H
04H
CYCLE_ACTIVITY.CYCLES_NO_EX
ECUTE
Cycles of dispatch stalls. Set AnyThread to count
per core.
Restricted to counters 03 when HTT is disabled.
A3H
05H
CYCLE_ACTIVITY.STALLS_L2_PEN Number of loads missed L2.
DING
Restricted to counters 03 when HTT is disabled.
A3H
06H
CYCLE_ACTIVITY.STALLS_LDM_P
ENDING
Restricted to counters 03 when HTT is disabled.
A3H
08H
CYCLE_ACTIVITY.CYCLES_L1D_PE Cycles with pending L1 cache miss loads. Set
NDING
AnyThread to count per core.
PMC2 only.
A3H
0CH
CYCLE_ACTIVITY.STALLS_L1D_PE Execution stalls due to L1 data cache miss loads.
NDING
Set Cmask=0CH.
PMC2 only.
A8H
01H
LSD.UOPS
Number of Uops delivered by the LSD.
ABH
01H
DSB2MITE_SWITCHES.COUNT
Number of DSB to MITE switches.
ABH
02H
DSB2MITE_SWITCHES.PENALTY_
CYCLES
Cycles DSB to MITE switches caused delay.
ACH
08H
DSB_FILL.EXCEED_DSB_LINES
DSB Fill encountered > 3 DSB lines.
AEH
01H
ITLB.ITLB_FLUSH
Counts the number of ITLB flushes, includes
4k/2M/4M pages.
B0H
01H
OFFCORE_REQUESTS.DEMAND_D Demand data read requests sent to uncore.
ATA_RD
B0H
02H
OFFCORE_REQUESTS.DEMAND_C Demand code read requests sent to uncore.
ODE_RD
B0H
04H
OFFCORE_REQUESTS.DEMAND_R Demand RFO read requests sent to uncore,
FO
including regular RFOs, locks, ItoM.
B0H
08H
OFFCORE_REQUESTS.ALL_DATA_ Data read requests sent to uncore (demand and
RD
prefetch).
B1H
01H
UOPS_EXECUTED.THREAD
Counts total number of uops to be executed perthread each cycle. Set Cmask = 1, INV =1 to count
stall cycles.
B1H
02H
UOPS_EXECUTED.CORE
Counts total number of uops to be executed percore each cycle.
Do not need to set ANY.
B7H
01H
OFFCORE_RESPONSE_0
See Section 18.9.5, “Off-core Response
Performance Monitoring”.
Requires MSR 01A6H.
BBH
01H
OFFCORE_RESPONSE_1
See Section 18.9.5, “Off-core Response
Performance Monitoring”.
Requires MSR 01A7H.
BDH
01H
TLB_FLUSH.DTLB_THREAD
DTLB flush attempts of the thread-specific entries.
BDH
20H
TLB_FLUSH.STLB_ANY
Count number of STLB flush attempts.
C0H
00H
INST_RETIRED.ANY_P
Number of instructions at retirement.
C0H
01H
INST_RETIRED.PREC_DIST
Precise instruction retired event with HW to reduce PMC1 only.
effect of PEBS shadow in IP distribution.
C1H
08H
OTHER_ASSISTS.AVX_STORE
Number of assists associated with 256-bit AVX
store operations.
C1H
10H
OTHER_ASSISTS.AVX_TO_SSE
Number of transitions from AVX-256 to legacy SSE
when penalty applicable.
See Table 19-1.
Vol. 3B 19-39
PERFORMANCE-MONITORING EVENTS
Table 19-11. Non-Architectural Performance Events In the Processor Core of
3rd Generation Intel® Core™ i7, i5, i3 Processors (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
C1H
20H
OTHER_ASSISTS.SSE_TO_AVX
Number of transitions from SSE to AVX-256 when
penalty applicable.
C1H
80H
OTHER_ASSISTS.WB
Number of times microcode assist is invoked by
hardware upon uop writeback.
C2H
01H
UOPS_RETIRED.ALL
Counts the number of micro-ops retired, Use
Supports PEBS, use
cmask=1 and invert to count active cycles or stalled Any=1 for core granular.
cycles.
C2H
02H
UOPS_RETIRED.RETIRE_SLOTS
Counts the number of retirement slots used each
cycle.
C3H
02H
MACHINE_CLEARS.MEMORY_ORD Counts the number of machine clears due to
ERING
memory order conflicts.
C3H
04H
MACHINE_CLEARS.SMC
Number of self-modifying-code machine clears
detected.
C3H
20H
MACHINE_CLEARS.MASKMOV
Counts the number of executed AVX masked load
operations that refer to an illegal address range
with the mask bits set to 0.
C4H
00H
BR_INST_RETIRED.ALL_BRANCH
ES
Branch instructions at retirement.
C4H
01H
BR_INST_RETIRED.CONDITIONAL Counts the number of conditional branch
instructions retired.
Supports PEBS.
C4H
02H
BR_INST_RETIRED.NEAR_CALL
Direct and indirect near call instructions retired.
Supports PEBS.
C4H
04H
BR_INST_RETIRED.ALL_BRANCH
ES
Counts the number of branch instructions retired.
Supports PEBS.
C4H
08H
BR_INST_RETIRED.NEAR_RETUR Counts the number of near return instructions
N
retired.
C4H
10H
BR_INST_RETIRED.NOT_TAKEN
Counts the number of not taken branch instructions Supports PEBS.
retired.
C4H
20H
BR_INST_RETIRED.NEAR_TAKEN
Number of near taken branches retired.
Comment
Supports PEBS.
See Table 19-1.
Supports PEBS.
Supports PEBS.
C4H
40H
BR_INST_RETIRED.FAR_BRANCH Number of far branches retired.
Supports PEBS.
C5H
00H
BR_MISP_RETIRED.ALL_BRANCH Mispredicted branch instructions at retirement.
ES
See Table 19-1.
C5H
01H
BR_MISP_RETIRED.CONDITIONAL Mispredicted conditional branch instructions retired. Supports PEBS.
C5H
04H
BR_MISP_RETIRED.ALL_BRANCH Mispredicted macro branch instructions retired.
ES
Supports PEBS.
C5H
20H
BR_MISP_RETIRED.NEAR_TAKEN Mispredicted taken branch instructions retired.
Supports PEBS.
CAH
02H
FP_ASSIST.X87_OUTPUT
Supports PEBS.
CAH
04H
FP_ASSIST.X87_INPUT
Number of X87 FP assists due to input values.
Supports PEBS.
CAH
08H
FP_ASSIST.SIMD_OUTPUT
Number of SIMD FP assists due to output values.
Supports PEBS.
CAH
10H
FP_ASSIST.SIMD_INPUT
Number of SIMD FP assists due to input values.
CAH
1EH
FP_ASSIST.ANY
Cycles with any input/output SSE* or FP assists.
CCH
20H
ROB_MISC_EVENTS.LBR_INSERT
S
Count cases of saving new LBR records by
hardware.
CDH
01H
MEM_TRANS_RETIRED.LOAD_LA
TENCY
Randomly sampled loads whose latency is above a
user defined threshold. A small fraction of the
overall loads are sampled due to randomization.
19-40 Vol. 3B
Number of X87 FP assists due to output values.
Specify threshold in MSR
3F6H. PMC 3 only.
PERFORMANCE-MONITORING EVENTS
Table 19-11. Non-Architectural Performance Events In the Processor Core of
3rd Generation Intel® Core™ i7, i5, i3 Processors (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
CDH
02H
MEM_TRANS_RETIRED.PRECISE_
STORE
Sample stores and collect precise store operation
via PEBS record. PMC3 only.
See Section 18.9.4.3.
D0H
11H
MEM_UOPS_RETIRED.STLB_MISS Retired load uops that miss the STLB.
_LOADS
Supports PEBS.
D0H
12H
MEM_UOPS_RETIRED.STLB_MISS Retired store uops that miss the STLB.
_STORES
Supports PEBS.
D0H
21H
MEM_UOPS_RETIRED.LOCK_LOA
DS
Retired load uops with locked access.
Supports PEBS.
D0H
41H
MEM_UOPS_RETIRED.SPLIT_LOA
DS
Retired load uops that split across a cacheline
boundary.
Supports PEBS.
D0H
42H
MEM_UOPS_RETIRED.SPLIT_STO
RES
Retired store uops that split across a cacheline
boundary.
Supports PEBS.
D0H
81H
MEM_UOPS_RETIRED.ALL_LOADS All retired load uops.
Supports PEBS.
D0H
82H
MEM_UOPS_RETIRED.ALL_STORE All retired store uops.
S
Supports PEBS.
D1H
01H
MEM_LOAD_UOPS_RETIRED.L1_
HIT
Retired load uops with L1 cache hits as data
sources.
Supports PEBS.
D1H
02H
MEM_LOAD_UOPS_RETIRED.L2_
HIT
Retired load uops with L2 cache hits as data
sources.
Supports PEBS.
D1H
04H
MEM_LOAD_UOPS_RETIRED.LLC_ Retired load uops whose data source was LLC hit
HIT
with no snoop required.
Supports PEBS.
D1H
08H
MEM_LOAD_UOPS_RETIRED.L1_
MISS
Retired load uops whose data source followed an
L1 miss.
Supports PEBS.
D1H
10H
MEM_LOAD_UOPS_RETIRED.L2_
MISS
Retired load uops that missed L2, excluding
unknown sources.
Supports PEBS.
D1H
20H
MEM_LOAD_UOPS_RETIRED.LLC_ Retired load uops whose data source is LLC miss.
MISS
D1H
40H
MEM_LOAD_UOPS_RETIRED.HIT_ Retired load uops which data sources were load
Supports PEBS.
LFB
uops missed L1 but hit FB due to preceding miss to
the same cache line with data not ready.
D2H
01H
MEM_LOAD_UOPS_LLC_HIT_RETI Retired load uops whose data source was an onRED.XSNP_MISS
package core cache LLC hit and cross-core snoop
missed.
Supports PEBS.
D2H
02H
MEM_LOAD_UOPS_LLC_HIT_RETI Retired load uops whose data source was an onRED.XSNP_HIT
package LLC hit and cross-core snoop hits.
Supports PEBS.
D2H
04H
MEM_LOAD_UOPS_LLC_HIT_RETI Retired load uops whose data source was an onRED.XSNP_HITM
package core cache with HitM responses.
Supports PEBS.
D2H
08H
MEM_LOAD_UOPS_LLC_HIT_RETI Retired load uops whose data source was LLC hit
RED.XSNP_NONE
with no snoop required.
Supports PEBS.
D3H
01H
MEM_LOAD_UOPS_LLC_MISS_RE
TIRED.LOCAL_DRAM
Supports PEBS.
Retired load uops whose data source was local
memory (cross-socket snoop not needed or missed).
E6H
1FH
BACLEARS.ANY
Number of front end re-steers due to BPU
misprediction.
F0H
01H
L2_TRANS.DEMAND_DATA_RD
Demand Data Read requests that access L2 cache.
F0H
02H
L2_TRANS.RFO
RFO requests that access L2 cache.
Supports PEBS.
Restricted to counters 03 when HTT is disabled.
Vol. 3B 19-41
PERFORMANCE-MONITORING EVENTS
Table 19-11. Non-Architectural Performance Events In the Processor Core of
3rd Generation Intel® Core™ i7, i5, i3 Processors (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
F0H
04H
L2_TRANS.CODE_RD
L2 cache accesses when fetching instructions.
F0H
08H
L2_TRANS.ALL_PF
Any MLC or LLC HW prefetch accessing L2, including
rejects.
F0H
10H
L2_TRANS.L1D_WB
L1D writebacks that access L2 cache.
F0H
20H
L2_TRANS.L2_FILL
L2 fill requests that access L2 cache.
F0H
40H
L2_TRANS.L2_WB
L2 writebacks that access L2 cache.
F0H
80H
L2_TRANS.ALL_REQUESTS
Transactions accessing L2 pipe.
F1H
01H
L2_LINES_IN.I
L2 cache lines in I state filling L2.
Counting does not cover
rejects.
F1H
02H
L2_LINES_IN.S
L2 cache lines in S state filling L2.
Counting does not cover
rejects.
F1H
04H
L2_LINES_IN.E
L2 cache lines in E state filling L2.
Counting does not cover
rejects.
F1H
07H
L2_LINES_IN.ALL
L2 cache lines filling L2.
Counting does not cover
rejects.
F2H
01H
L2_LINES_OUT.DEMAND_CLEAN
Clean L2 cache lines evicted by demand.
F2H
02H
L2_LINES_OUT.DEMAND_DIRTY
Dirty L2 cache lines evicted by demand.
F2H
04H
L2_LINES_OUT.PF_CLEAN
Clean L2 cache lines evicted by the MLC prefetcher.
F2H
08H
L2_LINES_OUT.PF_DIRTY
Dirty L2 cache lines evicted by the MLC prefetcher.
F2H
0AH
L2_LINES_OUT.DIRTY_ALL
Dirty L2 cache lines filling the L2.
19.5.1
Comment
Counting does not cover
rejects.
Performance Monitoring Events in the Processor Core of Intel Xeon Processor E5 v2
Family and Intel Xeon Processor E7 v2 Family
Non-architectural performance monitoring events in the processor core that are applicable only to Intel Xeon
processor E5 v2 family and Intel Xeon processor E7 v2 family based on the Ivy Bridge-E microarchitecture, with
CPUID signature of DisplayFamily_DisplayModel 06_3EH, are listed in Table 19-12.
Table 19-12. Non-Architectural Performance Events Applicable Only to the Processor Core of
Intel® Xeon® Processor E5 v2 Family and Intel® Xeon® Processor E7 v2 Family
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
D3H
03H
MEM_LOAD_UOPS_LLC_MISS_R
ETIRED.LOCAL_DRAM
Retired load uops whose data sources was local DRAM Supports PEBS.
(snoop not needed, Snoop Miss, or Snoop Hit data not
forwarded).
D3H
0CH
MEM_LOAD_UOPS_LLC_MISS_R
ETIRED.REMOTE_DRAM
Retired load uops whose data source was remote
DRAM (snoop not needed, Snoop Miss, or Snoop Hit
data not forwarded).
Supports PEBS.
D3H
10H
MEM_LOAD_UOPS_LLC_MISS_R
ETIRED.REMOTE_HITM
Retired load uops whose data sources was remote
HITM.
Supports PEBS.
D3H
20H
MEM_LOAD_UOPS_LLC_MISS_R
ETIRED.REMOTE_FWD
Retired load uops whose data sources was forwards
from a remote cache.
Supports PEBS.
19-42 Vol. 3B
Comment
PERFORMANCE-MONITORING EVENTS
19.6
PERFORMANCE MONITORING EVENTS FOR 2ND GENERATION
INTEL® CORE™ I7-2XXX, INTEL® CORE™ I5-2XXX, INTEL® CORE™ I3-2XXX
PROCESSOR SERIES
2nd generation Intel® Core™ i7-2xxx, Intel® Core™ i5-2xxx, Intel® Core™ i3-2xxx processor series, and Intel
Xeon processor E3-1200 product family are based on the Intel microarchitecture code name Sandy Bridge. They
support architectural performance-monitoring events listed in Table 19-1. Non-architectural performance-monitoring events in the processor core are listed in Table 19-13, Table 19-14, and Table 19-15. The events in Table
19-13 apply to processors with CPUID signature of DisplayFamily_DisplayModel encoding with the following
values: 06_2AH and 06_2DH. The events in Table 19-14 apply to processors with CPUID signature 06_2AH. The
events in Table 19-15 apply to processors with CPUID signature 06_2DH. Fixed counters in the core PMU support
the architecture events defined in Table 19-2.
Additional informations on event specifics (e.g. derivative events using specific IA32_PERFEVTSELx modifiers, limitations, special notes and recommendations) can be found at http://software.intel.com/en-us/forums/softwaretuning-performance-optimization-platform-monitoring.
Table 19-13. Non-Architectural Performance Events In the Processor Core Common to 2nd Generation Intel® Core™
i7-2xxx, Intel® Core™ i5-2xxx, Intel® Core™ i3-2xxx Processor Series and Intel® Xeon® Processors E3 and E5 Family
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
03H
01H
LD_BLOCKS.DATA_UNKNOWN
Blocked loads due to store buffer blocks with
unknown data.
03H
02H
LD_BLOCKS.STORE_FORWARD Loads blocked by overlapping with store buffer that
cannot be forwarded.
03H
08H
LD_BLOCKS.NO_SR
# of Split loads blocked due to resource not
available.
03H
10H
LD_BLOCKS.ALL_BLOCK
Number of cases where any load is blocked but has
no DCU miss.
05H
01H
MISALIGN_MEM_REF.LOADS
Speculative cache-line split load uops dispatched to
L1D.
05H
02H
MISALIGN_MEM_REF.STORES
Speculative cache-line split Store-address uops
dispatched to L1D.
07H
01H
LD_BLOCKS_PARTIAL.ADDRES False dependencies in MOB due to partial compare
S_ALIAS
on address.
07H
08H
LD_BLOCKS_PARTIAL.ALL_STA The number of times that load operations are
_BLOCK
temporarily blocked because of older stores, with
addresses that are not yet known. A load operation
may incur more than one block of this type.
08H
01H
DTLB_LOAD_MISSES.MISS_CA
USES_A_WALK
08H
02H
DTLB_LOAD_MISSES.WALK_CO Misses in all TLB levels that caused page walk
MPLETED
completed of any size.
08H
04H
DTLB_LOAD_MISSES.WALK_DU Cycle PMH is busy with a walk.
RATION
08H
10H
DTLB_LOAD_MISSES.STLB_HIT Number of cache load STLB hits. No page walk.
0DH
03H
INT_MISC.RECOVERY_CYCLES
Cycles waiting to recover after Machine Clears or
JEClear. Set Cmask= 1.
0DH
40H
INT_MISC.RAT_STALL_CYCLES
Cycles RAT external stall is sent to IDQ for this
thread.
Comment
Misses in all TLB levels that cause a page walk of
any page size.
Set Edge to count
occurrences.
Vol. 3B 19-43
PERFORMANCE-MONITORING EVENTS
Table 19-13. Non-Architectural Performance Events In the Processor Core Common to 2nd Generation Intel® Core™
i7-2xxx, Intel® Core™ i5-2xxx, Intel® Core™ i3-2xxx Processor Series and Intel® Xeon® Processors E3 and E5 Family
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
0EH
01H
UOPS_ISSUED.ANY
Increments each cycle the # of Uops issued by the
RAT to RS. Set Cmask = 1, Inv = 1, Any= 1to count
stalled cycles of this core.
Set Cmask = 1, Inv = 1to
count stalled cycles.
10H
01H
FP_COMP_OPS_EXE.X87
Counts number of X87 uops executed.
10H
10H
FP_COMP_OPS_EXE.SSE_FP_P Counts number of SSE* double precision FP packed
ACKED_DOUBLE
uops executed.
10H
20H
FP_COMP_OPS_EXE.SSE_FP_S Counts number of SSE* single precision FP scalar
CALAR_SINGLE
uops executed.
10H
40H
FP_COMP_OPS_EXE.SSE_PACK Counts number of SSE* single precision FP packed
ED SINGLE
uops executed.
10H
80H
FP_COMP_OPS_EXE.SSE_SCAL Counts number of SSE* double precision FP scalar
AR_DOUBLE
uops executed.
11H
01H
SIMD_FP_256.PACKED_SINGLE Counts 256-bit packed single-precision floatingpoint instructions.
11H
02H
SIMD_FP_256.PACKED_DOUBL Counts 256-bit packed double-precision floatingE
point instructions.
14H
01H
ARITH.FPU_DIV_ACTIVE
Cycles that the divider is active, includes INT and FP.
Set 'edge =1, cmask=1' to count the number of
divides.
17H
01H
INSTS_WRITTEN_TO_IQ.INSTS
Counts the number of instructions written into the
IQ every cycle.
24H
01H
L2_RQSTS.DEMAND_DATA_RD Demand Data Read requests that hit L2 cache.
_HIT
24H
03H
L2_RQSTS.ALL_DEMAND_DAT
A_RD
Counts any demand and L1 HW prefetch data load
requests to L2.
24H
04H
L2_RQSTS.RFO_HITS
Counts the number of store RFO requests that hit
the L2 cache.
24H
08H
L2_RQSTS.RFO_MISS
Counts the number of store RFO requests that miss
the L2 cache.
24H
0CH
L2_RQSTS.ALL_RFO
Counts all L2 store RFO requests.
24H
10H
L2_RQSTS.CODE_RD_HIT
Number of instruction fetches that hit the L2 cache.
24H
20H
L2_RQSTS.CODE_RD_MISS
Number of instruction fetches that missed the L2
cache.
24H
30H
L2_RQSTS.ALL_CODE_RD
Counts all L2 code requests.
24H
40H
L2_RQSTS.PF_HIT
Requests from L2 Hardware prefetcher that hit L2.
24H
80H
L2_RQSTS.PF_MISS
Requests from L2 Hardware prefetcher that missed
L2.
24H
C0H
L2_RQSTS.ALL_PF
Any requests from L2 Hardware prefetchers.
27H
01H
L2_STORE_LOCK_RQSTS.MISS
RFOs that miss cache lines.
27H
04H
L2_STORE_LOCK_RQSTS.HIT_
E
RFOs that hit cache lines in E state.
27H
08H
L2_STORE_LOCK_RQSTS.HIT_
M
RFOs that hit cache lines in M state.
27H
0FH
L2_STORE_LOCK_RQSTS.ALL
RFOs that access cache lines in any state.
19-44 Vol. 3B
PERFORMANCE-MONITORING EVENTS
Table 19-13. Non-Architectural Performance Events In the Processor Core Common to 2nd Generation Intel® Core™
i7-2xxx, Intel® Core™ i5-2xxx, Intel® Core™ i3-2xxx Processor Series and Intel® Xeon® Processors E3 and E5 Family
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
28H
01H
L2_L1D_WB_RQSTS.MISS
Not rejected writebacks from L1D to L2 cache lines
that missed L2.
28H
02H
L2_L1D_WB_RQSTS.HIT_S
Not rejected writebacks from L1D to L2 cache lines
in S state.
28H
04H
L2_L1D_WB_RQSTS.HIT_E
Not rejected writebacks from L1D to L2 cache lines
in E state.
28H
08H
L2_L1D_WB_RQSTS.HIT_M
Not rejected writebacks from L1D to L2 cache lines
in M state.
Not rejected writebacks from L1D to L2 cache.
Comment
28H
0FH
L2_L1D_WB_RQSTS.ALL
2EH
4FH
LONGEST_LAT_CACHE.REFERE This event counts requests originating from the
NCE
core that reference a cache line in the last level
cache.
See Table 19-1.
2EH
41H
LONGEST_LAT_CACHE.MISS
See Table 19-1.
3CH
00H
CPU_CLK_UNHALTED.THREAD Counts the number of thread cycles while the
_P
thread is not in a halt state. The thread enters the
halt state when it is running the HLT instruction.
The core frequency may change from time to time
due to power or thermal throttling.
See Table 19-1.
3CH
01H
CPU_CLK_THREAD_UNHALTED Increments at the frequency of XCLK (100 MHz)
.REF_XCLK
when not halted.
See Table 19-1.
48H
01H
L1D_PEND_MISS.PENDING
PMC2 only;
This event counts each cache miss condition for
references to the last level cache.
Increments the number of outstanding L1D misses
every cycle. Set Cmask = 1 and Edge =1 to count
occurrences.
49H
01H
DTLB_STORE_MISSES.MISS_CA Miss in all TLB levels causes an page walk of any
USES_A_WALK
page size (4K/2M/4M/1G).
49H
02H
DTLB_STORE_MISSES.WALK_C Miss in all TLB levels causes a page walk that
OMPLETED
completes of any page size (4K/2M/4M/1G).
49H
04H
DTLB_STORE_MISSES.WALK_D Cycles PMH is busy with this walk.
URATION
49H
10H
DTLB_STORE_MISSES.STLB_HI Store operations that miss the first TLB level but hit
T
the second and do not cause page walks.
4CH
01H
LOAD_HIT_PRE.SW_PF
Not SW-prefetch load dispatches that hit fill buffer
allocated for S/W prefetch.
4CH
02H
LOAD_HIT_PRE.HW_PF
Not SW-prefetch load dispatches that hit fill buffer
allocated for H/W prefetch.
4EH
02H
HW_PRE_REQ.DL1_MISS
Hardware Prefetch requests that miss the L1D
cache. A request is being counted each time it
access the cache & miss it, including if a block is
applicable or if hit the Fill Buffer for example.
51H
01H
L1D.REPLACEMENT
Counts the number of lines brought into the L1 data
cache.
51H
02H
L1D.ALLOCATED_IN_M
Counts the number of allocations of modified L1D
cache lines.
51H
04H
L1D.EVICTION
Counts the number of modified lines evicted from
the L1 data cache due to replacement.
Set Cmask = 1 to count
cycles.
This accounts for both L1
streamer and IP-based
(IPP) HW prefetchers.
Vol. 3B 19-45
PERFORMANCE-MONITORING EVENTS
Table 19-13. Non-Architectural Performance Events In the Processor Core Common to 2nd Generation Intel® Core™
i7-2xxx, Intel® Core™ i5-2xxx, Intel® Core™ i3-2xxx Processor Series and Intel® Xeon® Processors E3 and E5 Family
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
51H
08H
L1D.ALL_M_REPLACEMENT
Cache lines in M state evicted out of L1D due to
Snoop HitM or dirty line replacement.
59H
20H
PARTIAL_RAT_STALLS.FLAGS_ Increments the number of flags-merge uops in flight
MERGE_UOP
each cycle. Set Cmask = 1 to count cycles.
59H
40H
PARTIAL_RAT_STALLS.SLOW_
LEA_WINDOW
59H
80H
PARTIAL_RAT_STALLS.MUL_SI Number of Multiply packed/scalar single precision
NGLE_UOP
uops allocated.
5BH
0CH
RESOURCE_STALLS2.ALL_FL_
EMPTY
5BH
0FH
RESOURCE_STALLS2.ALL_PRF Cycles stalled due to control structures full for
_CONTROL
physical registers.
5BH
40H
RESOURCE_STALLS2.BOB_FUL Cycles Allocator is stalled due Branch Order Buffer.
L
5BH
4FH
RESOURCE_STALLS2.OOO_RS
RC
Cycles stalled due to out of order resources full.
5CH
01H
CPL_CYCLES.RING0
Unhalted core cycles when the thread is in ring 0.
5CH
02H
CPL_CYCLES.RING123
Unhalted core cycles when the thread is not in ring
0.
5EH
01H
RS_EVENTS.EMPTY_CYCLES
Cycles the RS is empty for the thread.
60H
01H
OFFCORE_REQUESTS_OUTSTA Offcore outstanding Demand Data Read
NDING.DEMAND_DATA_RD
transactions in SQ to uncore. Set Cmask=1 to count
cycles.
60H
04H
OFFCORE_REQUESTS_OUTSTA Offcore outstanding RFO store transactions in SQ to
NDING.DEMAND_RFO
uncore. Set Cmask=1 to count cycles.
60H
08H
OFFCORE_REQUESTS_OUTSTA Offcore outstanding cacheable data read
NDING.ALL_DATA_RD
transactions in SQ to uncore. Set Cmask=1 to count
cycles.
63H
01H
LOCK_CYCLES.SPLIT_LOCK_UC Cycles in which the L1D and L2 are locked, due to a
_LOCK_DURATION
UC lock or split lock.
63H
02H
LOCK_CYCLES.CACHE_LOCK_D
URATION
Cycles in which the L1D is locked.
79H
02H
IDQ.EMPTY
Counts cycles the IDQ is empty.
79H
04H
IDQ.MITE_UOPS
Increment each cycle # of uops delivered to IDQ
from MITE path. Set Cmask = 1 to count cycles.
Can combine Umask 04H
and 20H.
79H
08H
IDQ.DSB_UOPS
Increment each cycle. # of uops delivered to IDQ
from DSB path. Set Cmask = 1 to count cycles.
Can combine Umask 08H
and 10H.
79H
10H
IDQ.MS_DSB_UOPS
Increment each cycle # of uops delivered to IDQ
when MS busy by DSB. Set Cmask = 1 to count
cycles MS is busy. Set Cmask=1 and Edge =1 to
count MS activations.
Can combine Umask 08H
and 10H.
79H
20H
IDQ.MS_MITE_UOPS
Increment each cycle # of uops delivered to IDQ
when MS is busy by MITE. Set Cmask = 1 to count
cycles.
Can combine Umask 04H
and 20H.
19-46 Vol. 3B
Comment
Cycles with at least one slow LEA uop allocated.
Cycles stalled due to free list empty.
PMC0-3 only regardless
HTT.
Use Edge to count
transition.
PERFORMANCE-MONITORING EVENTS
Table 19-13. Non-Architectural Performance Events In the Processor Core Common to 2nd Generation Intel® Core™
i7-2xxx, Intel® Core™ i5-2xxx, Intel® Core™ i3-2xxx Processor Series and Intel® Xeon® Processors E3 and E5 Family
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
79H
30H
IDQ.MS_UOPS
Increment each cycle # of uops delivered to IDQ
from MS by either DSB or MITE. Set Cmask = 1 to
count cycles.
Can combine Umask 04H,
08H and 30H.
80H
02H
ICACHE.MISSES
Number of Instruction Cache, Streaming Buffer and
Victim Cache Misses. Includes UC accesses.
85H
01H
ITLB_MISSES.MISS_CAUSES_A
_WALK
Misses in all ITLB levels that cause page walks.
85H
02H
ITLB_MISSES.WALK_COMPLET
ED
Misses in all ITLB levels that cause completed page
walks.
85H
04H
ITLB_MISSES.WALK_DURATIO
N
Cycle PMH is busy with a walk.
85H
10H
ITLB_MISSES.STLB_HIT
Number of cache load STLB hits. No page walk.
87H
01H
ILD_STALL.LCP
Stalls caused by changing prefix length of the
instruction.
87H
04H
ILD_STALL.IQ_FULL
Stall cycles due to IQ is full.
88H
41H
BR_INST_EXEC.NONTAKEN_CO Not-taken macro conditional branches.
NDITIONAL
88H
81H
BR_INST_EXEC.TAKEN_CONDI
TIONAL
88H
82H
BR_INST_EXEC.TAKEN_DIRECT Taken speculative and retired conditional branches
_JUMP
excluding calls and indirects.
88H
84H
BR_INST_EXEC.TAKEN_INDIRE Taken speculative and retired indirect branches
CT_JUMP_NON_CALL_RET
excluding calls and returns.
88H
88H
BR_INST_EXEC.TAKEN_INDIRE Taken speculative and retired indirect branches that
CT_NEAR_RETURN
are returns.
88H
90H
BR_INST_EXEC.TAKEN_DIRECT Taken speculative and retired direct near calls.
_NEAR_CALL
88H
A0H
BR_INST_EXEC.TAKEN_INDIRE Taken speculative and retired indirect near calls.
CT_NEAR_CALL
88H
C1H
BR_INST_EXEC.ALL_CONDITIO Speculative and retired conditional branches.
NAL
88H
C2H
BR_INST_EXEC.ALL_DIRECT_J
UMP
Speculative and retired conditional branches
excluding calls and indirects.
88H
C4H
BR_INST_EXEC.ALL_INDIRECT
_JUMP_NON_CALL_RET
Speculative and retired indirect branches excluding
calls and returns.
88H
C8H
BR_INST_EXEC.ALL_INDIRECT
_NEAR_RETURN
Speculative and retired indirect branches that are
returns.
88H
D0H
BR_INST_EXEC.ALL_NEAR_CA
LL
Speculative and retired direct near calls.
88H
FFH
BR_INST_EXEC.ALL_BRANCHE Speculative and retired branches.
S
89H
41H
BR_MISP_EXEC.NONTAKEN_CO Not-taken mispredicted macro conditional branches.
NDITIONAL
89H
81H
BR_MISP_EXEC.TAKEN_CONDI
TIONAL
Taken speculative and retired conditional branches.
Taken speculative and retired mispredicted
conditional branches.
Vol. 3B 19-47
PERFORMANCE-MONITORING EVENTS
Table 19-13. Non-Architectural Performance Events In the Processor Core Common to 2nd Generation Intel® Core™
i7-2xxx, Intel® Core™ i5-2xxx, Intel® Core™ i3-2xxx Processor Series and Intel® Xeon® Processors E3 and E5 Family
Event
Num.
Umask
Value
89H
84H
BR_MISP_EXEC.TAKEN_INDIRE Taken speculative and retired mispredicted indirect
CT_JUMP_NON_CALL_RET
branches excluding calls and returns.
89H
88H
BR_MISP_EXEC.TAKEN_RETUR Taken speculative and retired mispredicted indirect
N_NEAR
branches that are returns.
89H
90H
BR_MISP_EXEC.TAKEN_DIRECT Taken speculative and retired mispredicted direct
_NEAR_CALL
near calls.
89H
A0H
BR_MISP_EXEC.TAKEN_INDIRE Taken speculative and retired mispredicted indirect
CT_NEAR_CALL
near calls.
89H
C1H
BR_MISP_EXEC.ALL_CONDITIO Speculative and retired mispredicted conditional
NAL
branches.
89H
C4H
BR_MISP_EXEC.ALL_INDIRECT
_JUMP_NON_CALL_RET
89H
D0H
BR_MISP_EXEC.ALL_NEAR_CA Speculative and retired mispredicted direct near
LL
calls.
89H
FFH
BR_MISP_EXEC.ALL_BRANCHE Speculative and retired mispredicted branches.
S
9CH
01H
IDQ_UOPS_NOT_DELIVERED.C
ORE
A1H
01H
UOPS_DISPATCHED_PORT.POR Cycles which a Uop is dispatched on port 0.
T_0
A1H
02H
UOPS_DISPATCHED_PORT.POR Cycles which a Uop is dispatched on port 1.
T_1
A1H
0CH
UOPS_DISPATCHED_PORT.POR Cycles which a Uop is dispatched on port 2.
T_2
A1H
30H
UOPS_DISPATCHED_PORT.POR Cycles which a Uop is dispatched on port 3.
T_3
A1H
40H
UOPS_DISPATCHED_PORT.POR Cycles which a Uop is dispatched on port 4.
T_4
A1H
80H
UOPS_DISPATCHED_PORT.POR Cycles which a Uop is dispatched on port 5.
T_5
A2H
01H
RESOURCE_STALLS.ANY
Cycles Allocation is stalled due to Resource Related
reason.
A2H
02H
RESOURCE_STALLS.LB
Counts the cycles of stall due to lack of load buffers.
A2H
04H
RESOURCE_STALLS.RS
Cycles stalled due to no eligible RS entry available.
A2H
08H
RESOURCE_STALLS.SB
Cycles stalled due to no store buffers available (not
including draining form sync).
A2H
10H
RESOURCE_STALLS.ROB
Cycles stalled due to re-order buffer full.
A2H
20H
RESOURCE_STALLS.FCSW
Cycles stalled due to writing the FPU control word.
A3H
02H
CYCLE_ACTIVITY.CYCLES_L1D_ Cycles with pending L1 cache miss loads. Set
PENDING
AnyThread to count per core.
A3H
01H
CYCLE_ACTIVITY.CYCLES_L2_P Cycles with pending L2 miss loads. Set AnyThread
ENDING
to count per core.
A3H
04H
CYCLE_ACTIVITY.CYCLES_NO_
DISPATCH
19-48 Vol. 3B
Event Mask Mnemonic
Description
Comment
Speculative and retired mispredicted indirect
branches excluding calls and returns.
Count issue pipeline slots where no uop was
delivered from the front end to the back end when
there is no back-end stall.
Use Cmask to qualify uop
b/w.
PMC2 only.
Cycles of dispatch stalls. Set AnyThread to count per PMC0-3 only.
core.
PERFORMANCE-MONITORING EVENTS
Table 19-13. Non-Architectural Performance Events In the Processor Core Common to 2nd Generation Intel® Core™
i7-2xxx, Intel® Core™ i5-2xxx, Intel® Core™ i3-2xxx Processor Series and Intel® Xeon® Processors E3 and E5 Family
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
A8H
01H
LSD.UOPS
Number of Uops delivered by the LSD.
ABH
01H
DSB2MITE_SWITCHES.COUNT
Number of DSB to MITE switches.
ABH
02H
DSB2MITE_SWITCHES.PENALT
Y_CYCLES
Cycles DSB to MITE switches caused delay.
ACH
02H
DSB_FILL.OTHER_CANCEL
Cases of cancelling valid DSB fill not because of
exceeding way limit.
ACH
08H
DSB_FILL.EXCEED_DSB_LINES
DSB Fill encountered > 3 DSB lines.
AEH
01H
ITLB.ITLB_FLUSH
Counts the number of ITLB flushes; includes
4k/2M/4M pages.
B0H
01H
OFFCORE_REQUESTS.DEMAND Demand data read requests sent to uncore.
_DATA_RD
B0H
04H
OFFCORE_REQUESTS.DEMAND Demand RFO read requests sent to uncore, including
_RFO
regular RFOs, locks, ItoM.
B0H
08H
OFFCORE_REQUESTS.ALL_DAT Data read requests sent to uncore (demand and
A_RD
prefetch).
B1H
01H
UOPS_DISPATCHED.THREAD
Counts total number of uops to be dispatched perthread each cycle. Set Cmask = 1, INV =1 to count
stall cycles.
PMC0-3 only regardless
HTT.
B1H
02H
UOPS_DISPATCHED.CORE
Counts total number of uops to be dispatched percore each cycle.
Do not need to set ANY.
B2H
01H
OFFCORE_REQUESTS_BUFFER Offcore requests buffer cannot take more entries
.SQ_FULL
for this thread core.
B6H
01H
AGU_BYPASS_CANCEL.COUNT
Counts executed load operations with all the
following traits: 1. addressing of the format [base +
offset], 2. the offset is between 1 and 2047, 3. the
address specified in the base register is in one page
and the address [base+offset] is in another page.
B7H
01H
OFF_CORE_RESPONSE_0
See Section 18.9.5, “Off-core Response
Performance Monitoring”.
Requires MSR 01A6H.
BBH
01H
OFF_CORE_RESPONSE_1
See Section 18.9.5, “Off-core Response
Performance Monitoring”.
Requires MSR 01A7H.
BDH
01H
TLB_FLUSH.DTLB_THREAD
DTLB flush attempts of the thread-specific entries.
BDH
20H
TLB_FLUSH.STLB_ANY
Count number of STLB flush attempts.
BFH
05H
L1D_BLOCKS.BANK_CONFLICT Cycles when dispatched loads are cancelled due to
_CYCLES
L1D bank conflicts with other load ports.
cmask=1.
C0H
00H
INST_RETIRED.ANY_P
Number of instructions at retirement.
See Table 19-1.
C0H
01H
INST_RETIRED.PREC_DIST
Precise instruction retired event with HW to reduce PMC1 only; Must quiesce
effect of PEBS shadow in IP distribution.
other PMCs.
C1H
02H
OTHER_ASSISTS.ITLB_MISS_R
ETIRED
Instructions that experienced an ITLB miss.
C1H
08H
OTHER_ASSISTS.AVX_STORE
Number of assists associated with 256-bit AVX
store operations.
C1H
10H
OTHER_ASSISTS.AVX_TO_SSE Number of transitions from AVX-256 to legacy SSE
when penalty applicable.
Comment
Vol. 3B 19-49
PERFORMANCE-MONITORING EVENTS
Table 19-13. Non-Architectural Performance Events In the Processor Core Common to 2nd Generation Intel® Core™
i7-2xxx, Intel® Core™ i5-2xxx, Intel® Core™ i3-2xxx Processor Series and Intel® Xeon® Processors E3 and E5 Family
Event
Num.
Umask
Value
C1H
20H
OTHER_ASSISTS.SSE_TO_AVX Number of transitions from SSE to AVX-256 when
penalty applicable.
C2H
01H
UOPS_RETIRED.ALL
C2H
02H
UOPS_RETIRED.RETIRE_SLOTS Counts the number of retirement slots used each
cycle.
C3H
02H
MACHINE_CLEARS.MEMORY_O Counts the number of machine clears due to
RDERING
memory order conflicts.
C3H
04H
MACHINE_CLEARS.SMC
Counts the number of times that a program writes
to a code section.
C3H
20H
MACHINE_CLEARS.MASKMOV
Counts the number of executed AVX masked load
operations that refer to an illegal address range
with the mask bits set to 0.
C4H
00H
BR_INST_RETIRED.ALL_BRAN
CHES
Branch instructions at retirement.
C4H
01H
BR_INST_RETIRED.CONDITION Counts the number of conditional branch
AL
instructions retired.
Supports PEBS.
C4H
02H
BR_INST_RETIRED.NEAR_CALL Direct and indirect near call instructions retired.
Supports PEBS.
C4H
04H
BR_INST_RETIRED.ALL_BRAN
CHES
Counts the number of branch instructions retired.
Supports PEBS.
C4H
08H
BR_INST_RETIRED.NEAR_RET
URN
Counts the number of near return instructions
retired.
Supports PEBS.
C4H
10H
BR_INST_RETIRED.NOT_TAKE
N
Counts the number of not taken branch instructions
retired.
C4H
20H
BR_INST_RETIRED.NEAR_TAK
EN
Number of near taken branches retired.
C4H
40H
BR_INST_RETIRED.FAR_BRAN
CH
Number of far branches retired.
C5H
00H
BR_MISP_RETIRED.ALL_BRAN
CHES
Mispredicted branch instructions at retirement.
C5H
01H
BR_MISP_RETIRED.CONDITION Mispredicted conditional branch instructions retired. Supports PEBS.
AL
C5H
02H
BR_MISP_RETIRED.NEAR_CAL
L
Direct and indirect mispredicted near call
instructions retired.
Supports PEBS.
C5H
04H
BR_MISP_RETIRED.ALL_BRAN
CHES
Mispredicted macro branch instructions retired.
Supports PEBS.
C5H
10H
BR_MISP_RETIRED.NOT_TAKE
N
Mispredicted not taken branch instructions retired.
Supports PEBS.
C5H
20H
BR_MISP_RETIRED.TAKEN
Mispredicted taken branch instructions retired.
Supports PEBS.
CAH
02H
FP_ASSIST.X87_OUTPUT
Number of X87 assists due to output value.
CAH
04H
FP_ASSIST.X87_INPUT
Number of X87 assists due to input value.
CAH
08H
FP_ASSIST.SIMD_OUTPUT
Number of SIMD FP assists due to output values.
CAH
10H
FP_ASSIST.SIMD_INPUT
Number of SIMD FP assists due to input values.
CAH
1EH
FP_ASSIST.ANY
Cycles with any input/output SSE* or FP assists.
19-50 Vol. 3B
Event Mask Mnemonic
Description
Comment
Counts the number of micro-ops retired, Use
Supports PEBS.
cmask=1 and invert to count active cycles or stalled
cycles.
Supports PEBS.
See Table 19-1.
Supports PEBS.
See Table 19-1.
PERFORMANCE-MONITORING EVENTS
Table 19-13. Non-Architectural Performance Events In the Processor Core Common to 2nd Generation Intel® Core™
i7-2xxx, Intel® Core™ i5-2xxx, Intel® Core™ i3-2xxx Processor Series and Intel® Xeon® Processors E3 and E5 Family
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
CCH
20H
ROB_MISC_EVENTS.LBR_INSE
RTS
Count cases of saving new LBR records by
hardware.
CDH
01H
MEM_TRANS_RETIRED.LOAD_
LATENCY
Randomly sampled loads whose latency is above a
user defined threshold. A small fraction of the
overall loads are sampled due to randomization.
PMC3 only.
CDH
02H
MEM_TRANS_RETIRED.PRECIS Sample stores and collect precise store operation
E_STORE
via PEBS record. PMC3 only.
See Section 18.9.4.3.
D0H
11H
MEM_UOPS_RETIRED.STLB_MI Retired load uops that miss the STLB.
SS_LOADS
Supports PEBS. PMC0-3
only regardless HTT.
D0H
12H
MEM_UOPS_RETIRED.STLB_MI Retired store uops that miss the STLB.
SS_STORES
Supports PEBS. PMC0-3
only regardless HTT.
D0H
21H
MEM_UOPS_RETIRED.LOCK_LO Retired load uops with locked access.
ADS
Supports PEBS. PMC0-3
only regardless HTT.
D0H
41H
MEM_UOPS_RETIRED.SPLIT_L
OADS
Retired load uops that split across a cacheline
boundary.
Supports PEBS. PMC0-3
only regardless HTT.
D0H
42H
MEM_UOPS_RETIRED.SPLIT_S
TORES
Retired store uops that split across a cacheline
boundary.
Supports PEBS. PMC0-3
only regardless HTT.
D0H
81H
MEM_UOPS_RETIRED.ALL_LOA All retired load uops.
DS
Supports PEBS. PMC0-3
only regardless HTT.
D0H
82H
MEM_UOPS_RETIRED.ALL_STO All retired store uops.
RES
Supports PEBS. PMC0-3
only regardless HTT.
D1H
01H
MEM_LOAD_UOPS_RETIRED.L
1_HIT
Retired load uops with L1 cache hits as data
sources.
Supports PEBS. PMC0-3
only regardless HTT.
D1H
02H
MEM_LOAD_UOPS_RETIRED.L
2_HIT
Retired load uops with L2 cache hits as data
sources.
Supports PEBS.
D1H
04H
MEM_LOAD_UOPS_RETIRED.LL Retired load uops which data sources were data hits Supports PEBS.
C_HIT
in LLC without snoops required.
D1H
20H
MEM_LOAD_UOPS_RETIRED.LL Retired load uops which data sources were data
C_MISS
missed LLC (excluding unknown data source).
Supports PEBS.
D1H
40H
MEM_LOAD_UOPS_RETIRED.HI Retired load uops which data sources were load
T_LFB
uops missed L1 but hit FB due to preceding miss to
the same cache line with data not ready.
Supports PEBS.
D2H
01H
MEM_LOAD_UOPS_LLC_HIT_R
ETIRED.XSNP_MISS
Retired load uops whose data source was an onpackage core cache LLC hit and cross-core snoop
missed.
Supports PEBS.
D2H
02H
MEM_LOAD_UOPS_LLC_HIT_R
ETIRED.XSNP_HIT
Retired load uops whose data source was an onpackage LLC hit and cross-core snoop hits.
Supports PEBS.
D2H
04H
MEM_LOAD_UOPS_LLC_HIT_R
ETIRED.XSNP_HITM
Retired load uops whose data source was an onpackage core cache with HitM responses.
Supports PEBS.
D2H
08H
MEM_LOAD_UOPS_LLC_HIT_R
ETIRED.XSNP_NONE
Retired load uops whose data source was LLC hit
with no snoop required.
Supports PEBS.
E6H
01H
BACLEARS.ANY
Counts the number of times the front end is resteered, mainly when the BPU cannot provide a
correct prediction and this is corrected by other
branch handling mechanisms at the front end.
F0H
01H
L2_TRANS.DEMAND_DATA_RD Demand Data Read requests that access L2 cache.
Comment
Specify threshold in MSR
3F6H.
Vol. 3B 19-51
PERFORMANCE-MONITORING EVENTS
Table 19-13. Non-Architectural Performance Events In the Processor Core Common to 2nd Generation Intel® Core™
i7-2xxx, Intel® Core™ i5-2xxx, Intel® Core™ i3-2xxx Processor Series and Intel® Xeon® Processors E3 and E5 Family
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
F0H
02H
L2_TRANS.RFO
RFO requests that access L2 cache.
F0H
04H
L2_TRANS.CODE_RD
L2 cache accesses when fetching instructions.
F0H
08H
L2_TRANS.ALL_PF
L2 or LLC HW prefetches that access L2 cache.
F0H
10H
L2_TRANS.L1D_WB
L1D writebacks that access L2 cache.
F0H
20H
L2_TRANS.L2_FILL
L2 fill requests that access L2 cache.
F0H
40H
L2_TRANS.L2_WB
L2 writebacks that access L2 cache.
F0H
80H
L2_TRANS.ALL_REQUESTS
Transactions accessing L2 pipe.
F1H
01H
L2_LINES_IN.I
L2 cache lines in I state filling L2.
Counting does not cover
rejects.
F1H
02H
L2_LINES_IN.S
L2 cache lines in S state filling L2.
Counting does not cover
rejects.
F1H
04H
L2_LINES_IN.E
L2 cache lines in E state filling L2.
Counting does not cover
rejects.
F1H
07H
L2_LINES_IN.ALL
L2 cache lines filling L2.
Counting does not cover
rejects.
F2H
01H
L2_LINES_OUT.DEMAND_CLEA Clean L2 cache lines evicted by demand.
N
F2H
02H
L2_LINES_OUT.DEMAND_DIRT
Y
Dirty L2 cache lines evicted by demand.
F2H
04H
L2_LINES_OUT.PF_CLEAN
Clean L2 cache lines evicted by L2 prefetch.
F2H
08H
L2_LINES_OUT.PF_DIRTY
Dirty L2 cache lines evicted by L2 prefetch.
F2H
0AH
L2_LINES_OUT.DIRTY_ALL
Dirty L2 cache lines filling the L2.
F4H
10H
SQ_MISC.SPLIT_LOCK
Split locks in SQ.
Comment
Including rejects.
Counting does not cover
rejects.
Non-architecture performance monitoring events in the processor core that are applicable only to Intel processors
with CPUID signature of DisplayFamily_DisplayModel 06_2AH are listed in Table 19-14.
Table 19-14. Non-Architectural Performance Events applicable only to the Processor core for 2nd Generation Intel®
Core™ i7-2xxx, Intel® Core™ i5-2xxx, Intel® Core™ i3-2xxx Processor Series
Event
Num.
Umask
Value
D2H
01H
MEM_LOAD_UOPS_LLC_HIT_R Retired load uops which data sources were LLC hit and Supports PEBS. PMC0ETIRED.XSNP_MISS
cross-core snoop missed in on-pkg core cache.
3 only regardless HTT.
D2H
02H
MEM_LOAD_UOPS_LLC_HIT_R Retired load uops which data sources were LLC and
ETIRED.XSNP_HIT
cross-core snoop hits in on-pkg core cache.
Supports PEBS.
D2H
04H
MEM_LOAD_UOPS_LLC_HIT_R Retired load uops which data sources were HitM
ETIRED.XSNP_HITM
responses from shared LLC.
Supports PEBS.
D2H
08H
MEM_LOAD_UOPS_LLC_HIT_R Retired load uops which data sources were hits in LLC
ETIRED.XSNP_NONE
without snoops required.
Supports PEBS.
D4H
02H
MEM_LOAD_UOPS_MISC_RETI
RED.LLC_MISS
Retired load uops with unknown information as data
source in cache serviced the load.
Supports PEBS. PMC03 only regardless HTT.
OFF_CORE_RESPONSE_N
Sub-events of OFF_CORE_RESPONSE_N (suffix N = 0,
1) programmed using MSR 01A6H/01A7H with values
shown in the comment column.
B7H/BBH 01H
19-52 Vol. 3B
Event Mask Mnemonic
Description
Comment
PERFORMANCE-MONITORING EVENTS
Table 19-14. Non-Architectural Performance Events applicable only to the Processor core for 2nd Generation Intel®
Core™ i7-2xxx, Intel® Core™ i5-2xxx, Intel® Core™ i3-2xxx Processor Series (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
OFFCORE_RESPONSE.ALL_CODE_RD.LLC_HIT_N
10003C0244H
OFFCORE_RESPONSE.ALL_CODE_RD.LLC_HIT.NO_SNOOP_NEEDED_N
1003C0244H
OFFCORE_RESPONSE.ALL_CODE_RD.LLC_HIT.SNOOP_MISS_N
2003C0244H
OFFCORE_RESPONSE.ALL_CODE_RD.LLC_HIT.MISS_DRAM_N
300400244H
OFFCORE_RESPONSE.ALL_DATA_RD.LLC_HIT.ANY_RESPONSE_N
3F803C0091H
OFFCORE_RESPONSE.ALL_DATA_RD.LLC_MISS.DRAM_N
300400091H
OFFCORE_RESPONSE.ALL_PF_CODE_RD.LLC_HIT.ANY_RESPONSE_N
3F803C0240H
OFFCORE_RESPONSE.ALL_PF_CODE_RD.LLC_HIT.HIT_OTHER_CORE_NO_FWD_N
4003C0240H
OFFCORE_RESPONSE.ALL_PF_CODE_RD.LLC_HIT.HITM_OTHER_CORE_N
10003C0240H
OFFCORE_RESPONSE.ALL_PF_CODE_RD.LLC_HIT.NO_SNOOP_NEEDED_N
1003C0240H
OFFCORE_RESPONSE.ALL_PF_CODE_RD.LLC_HIT.SNOOP_MISS_N
2003C0240H
OFFCORE_RESPONSE.ALL_PF_CODE_RD.LLC_MISS.DRAM_N
300400240H
OFFCORE_RESPONSE.ALL_PF_DATA_RD.LLC_MISS.DRAM_N
300400090H
OFFCORE_RESPONSE.ALL_PF_RFO.LLC_HIT.ANY_RESPONSE_N
3F803C0120H
OFFCORE_RESPONSE.ALL_PF_RFO.LLC_HIT.HIT_OTHER_CORE_NO_FWD_N
4003C0120H
OFFCORE_RESPONSE.ALL_PF_RFO.LLC_HIT.HITM_OTHER_CORE_N
10003C0120H
OFFCORE_RESPONSE.ALL_PF_RfO.LLC_HIT.NO_SNOOP_NEEDED_N
1003C0120H
OFFCORE_RESPONSE.ALL_PF_RFO.LLC_HIT.SNOOP_MISS_N
2003C0120H
OFFCORE_RESPONSE.ALL_PF_RFO.LLC_MISS.DRAM_N
300400120H
OFFCORE_RESPONSE.ALL_READS.LLC_MISS.DRAM_N
3004003F7H
OFFCORE_RESPONSE.ALL_RFO.LLC_HIT.ANY_RESPONSE_N
3F803C0122H
OFFCORE_RESPONSE.ALL_RFO.LLC_HIT.HIT_OTHER_CORE_NO_FWD_N
4003C0122H
OFFCORE_RESPONSE.ALL_RFO.LLC_HIT.HITM_OTHER_CORE_N
10003C0122H
OFFCORE_RESPONSE.ALL_RFO.LLC_HIT.NO_SNOOP_NEEDED_N
1003C0122H
OFFCORE_RESPONSE.ALL_RFO.LLC_HIT.SNOOP_MISS_N
2003C0122H
OFFCORE_RESPONSE.ALL_RFO.LLC_MISS.DRAM_N
300400122H
OFFCORE_RESPONSE.DEMAND_CODE_RD.LLC_HIT.HIT_OTHER_CORE_NO_FWD_N
4003C0004H
OFFCORE_RESPONSE.DEMAND_CODE_RD.LLC_HIT.HITM_OTHER_CORE_N
10003C0004H
OFFCORE_RESPONSE.DEMAND_CODE_RD.LLC_HIT.NO_SNOOP_NEEDED_N
1003C0004H
OFFCORE_RESPONSE.DEMAND_CODE_RD.LLC_HIT.SNOOP_MISS_N
2003C0004H
OFFCORE_RESPONSE.DEMAND_CODE_RD.LLC_MISS.DRAM_N
300400004H
OFFCORE_RESPONSE.DEMAND_DATA_RD.LLC_MISS.DRAM_N
300400001H
OFFCORE_RESPONSE.DEMAND_RFO.LLC_HIT.ANY_RESPONSE_N
3F803C0002H
OFFCORE_RESPONSE.DEMAND_RFO.LLC_HIT.HIT_OTHER_CORE_NO_FWD_N
4003C0002H
OFFCORE_RESPONSE.DEMAND_RFO.LLC_HIT.HITM_OTHER_CORE_N
10003C0002H
OFFCORE_RESPONSE.DEMAND_RFO.LLC_HIT.NO_SNOOP_NEEDED_N
1003C0002H
OFFCORE_RESPONSE.DEMAND_RFO.LLC_HIT.SNOOP_MISS_N
2003C0002H
OFFCORE_RESPONSE.DEMAND_RFO.LLC_MISS.DRAM_N
300400002H
OFFCORE_RESPONSE.OTHER.ANY_RESPONSE_N
18000H
OFFCORE_RESPONSE.PF_L2_CODE_RD.LLC_HIT.HIT_OTHER_CORE_NO_FWD_N
4003C0040H
Vol. 3B 19-53
PERFORMANCE-MONITORING EVENTS
Table 19-14. Non-Architectural Performance Events applicable only to the Processor core for 2nd Generation Intel®
Core™ i7-2xxx, Intel® Core™ i5-2xxx, Intel® Core™ i3-2xxx Processor Series (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
OFFCORE_RESPONSE.PF_L2_CODE_RD.LLC_HIT.HITM_OTHER_CORE_N
10003C0040H
OFFCORE_RESPONSE.PF_L2_CODE_RD.LLC_HIT.NO_SNOOP_NEEDED_N
1003C0040H
OFFCORE_RESPONSE.PF_L2_CODE_RD.LLC_HIT.SNOOP_MISS_N
2003C0040H
OFFCORE_RESPONSE.PF_L2_CODE_RD.LLC_MISS.DRAM_N
300400040H
OFFCORE_RESPONSE.PF_L2_DATA_RD.LLC_MISS.DRAM_N
300400010H
OFFCORE_RESPONSE.PF_L2_RFO.LLC_HIT.ANY_RESPONSE_N
3F803C0020H
OFFCORE_RESPONSE.PF_L2_RFO.LLC_HIT.HIT_OTHER_CORE_NO_FWD_N
4003C0020H
OFFCORE_RESPONSE.PF_L2_RFO.LLC_HIT.HITM_OTHER_CORE_N
10003C0020H
OFFCORE_RESPONSE.PF_L2_RFO.LLC_HIT.NO_SNOOP_NEEDED_N
1003C0020H
OFFCORE_RESPONSE.PF_L2_RFO.LLC_HIT.SNOOP_MISS_N
2003C0020H
OFFCORE_RESPONSE.PF_L2_RFO.LLC_MISS.DRAM_N
300400020H
OFFCORE_RESPONSE.PF_LLC_CODE_RD.LLC_HIT.HIT_OTHER_CORE_NO_FWD_N
4003C0200H
OFFCORE_RESPONSE.PF_LLC_CODE_RD.LLC_HIT.HITM_OTHER_CORE_N
10003C0200H
OFFCORE_RESPONSE.PF_LLC_CODE_RD.LLC_HIT.NO_SNOOP_NEEDED_N
1003C0200H
OFFCORE_RESPONSE.PF_LLC_CODE_RD.LLC_HIT.SNOOP_MISS_N
2003C0200H
OFFCORE_RESPONSE.PF_LLC_CODE_RD.LLC_MISS.DRAM_N
300400200H
OFFCORE_RESPONSE.PF_LLC_DATA_RD.LLC_MISS.DRAM_N
300400080H
OFFCORE_RESPONSE.PF_LLC_RFO.LLC_HIT.ANY_RESPONSE_N
3F803C0100H
OFFCORE_RESPONSE.PF_LLC_RFO.LLC_HIT.HIT_OTHER_CORE_NO_FWD_N
4003C0100H
OFFCORE_RESPONSE.PF_LLC_RFO.LLC_HIT.HITM_OTHER_CORE_N
10003C0100H
OFFCORE_RESPONSE.PF_LLC_RFO.LLC_HIT.NO_SNOOP_NEEDED_N
1003C0100H
OFFCORE_RESPONSE.PF_LLC_RFO.LLC_HIT.SNOOP_MISS_N
2003C0100H
OFFCORE_RESPONSE.PF_LLC_RFO.LLC_MISS.DRAM_N
300400100H
Non-architecture performance monitoring events in the processor core that are applicable only to Intel Xeon
processor E5 family (and Intel Core i7-3930 processor) based on Intel microarchitecture code name Sandy Bridge,
with CPUID signature of DisplayFamily_DisplayModel 06_2DH, are listed in Table 19-15.
Table 19-15. Non-Architectural Performance Events Applicable only to the Processor Core of
Intel® Xeon® Processor E5 Family
Event
Num.
Umask
Value
CDH
Event Mask Mnemonic
Description
01H
MEM_TRANS_RETIRED.LOAD_
LATENCY
Additional Configuration: Disable BL bypass and direct2core, and if the memory
is remotely homed. The count is not reliable If the memory is locally homed.
D1H
04H
MEM_LOAD_UOPS_RETIRED.LL Additional Configuration: Disable BL bypass. Supports PEBS.
C_HIT
D1H
20H
MEM_LOAD_UOPS_RETIRED.LL Additional Configuration: Disable BL bypass and direct2core. Supports PEBS.
C_MISS
D2H
01H
MEM_LOAD_UOPS_LLC_HIT_R Additional Configuration: Disable bypass. Supports PEBS.
ETIRED.XSNP_MISS
D2H
02H
MEM_LOAD_UOPS_LLC_HIT_R Additional Configuration: Disable bypass. Supports PEBS.
ETIRED.XSNP_HIT
19-54 Vol. 3B
Comment
PERFORMANCE-MONITORING EVENTS
Table 19-15. Non-Architectural Performance Events Applicable only to the Processor Core of
Intel® Xeon® Processor E5 Family
Event
Num.
Umask
Value
D2H
04H
MEM_LOAD_UOPS_LLC_HIT_R Additional Configuration: Disable bypass. Supports PEBS.
ETIRED.XSNP_HITM
D2H
08H
MEM_LOAD_UOPS_LLC_HIT_R Additional Configuration: Disable bypass. Supports PEBS.
ETIRED.XSNP_NONE
D3H
01H
MEM_LOAD_UOPS_LLC_MISS_
RETIRED.LOCAL_DRAM
Retired load uops which data sources were data
missed LLC but serviced by local DRAM. Supports
PEBS.
Disable BL bypass and
direct2core (see MSR
3C9H).
D3H
04H
MEM_LOAD_UOPS_LLC_MISS_
RETIRED.REMOTE_DRAM
Retired load uops which data sources were data
missed LLC but serviced by remote DRAM. Supports
PEBS.
Disable BL bypass and
direct2core (see MSR
3C9H).
OFF_CORE_RESPONSE_N
Sub-events of OFF_CORE_RESPONSE_N (suffix N = 0,
1) programmed using MSR 01A6H/01A7H with values
shown in the comment column.
B7H/BB 01H
H
Event Mask Mnemonic
Description
Comment
OFFCORE_RESPONSE.DEMAND_CODE_RD.LLC_MISS.ANY_RESPONSE_N
3FFFC00004H
OFFCORE_RESPONSE.DEMAND_CODE_RD.LLC_MISS.LOCAL_DRAM_N
600400004H
OFFCORE_RESPONSE.DEMAND_CODE_RD.LLC_MISS.REMOTE_DRAM_N
67F800004H
OFFCORE_RESPONSE.DEMAND_CODE_RD.LLC_MISS.REMOTE_HIT_FWD_N
87F800004H
OFFCORE_RESPONSE.DEMAND_CODE_RD.LLC_MISS.REMOTE_HITM_N
107FC00004H
OFFCORE_RESPONSE.DEMAND_DATA_RD.LLC_MISS.ANY_DRAM_N
67FC00001H
OFFCORE_RESPONSE.DEMAND_DATA_RD.LLC_MISS.ANY_RESPONSE_N
3F803C0001H
OFFCORE_RESPONSE.DEMAND_DATA_RD.LLC_MISS.LOCAL_DRAM_N
600400001H
OFFCORE_RESPONSE.DEMAND_DATA_RD.LLC_MISS.REMOTE_DRAM_N
67F800001H
OFFCORE_RESPONSE.DEMAND_DATA_RD.LLC_MISS.REMOTE_HIT_FWD_N
87F800001H
OFFCORE_RESPONSE.DEMAND_DATA_RD.LLC_MISS.REMOTE_HITM_N
107FC00001H
OFFCORE_RESPONSE.PF_L2_CODE_RD.LLC_MISS.ANY_RESPONSE_N
3F803C0040H
OFFCORE_RESPONSE.PF_L2_DATA_RD.LLC_MISS.ANY_DRAM_N
67FC00010H
OFFCORE_RESPONSE.PF_L2_DATA_RD.LLC_MISS.ANY_RESPONSE_N
3F803C0010H
OFFCORE_RESPONSE.PF_L2_DATA_RD.LLC_MISS.LOCAL_DRAM_N
600400010H
OFFCORE_RESPONSE.PF_L2_DATA_RD.LLC_MISS.REMOTE_DRAM_N
67F800010H
OFFCORE_RESPONSE.PF_L2_DATA_RD.LLC_MISS.REMOTE_HIT_FWD_N
87F800010H
OFFCORE_RESPONSE.PF_L2_DATA_RD.LLC_MISS.REMOTE_HITM_N
107FC00010H
OFFCORE_RESPONSE.PF_LLC_CODE_RD.LLC_MISS.ANY_RESPONSE_N
3FFFC00200H
OFFCORE_RESPONSE.PF_LLC_DATA_RD.LLC_MISS.ANY_RESPONSE_N
3FFFC00080H
Non-architectural Performance monitoring events that are located in the uncore sub-system are implementation
specific between different platforms using processors based on Intel microarchitecture code name Sandy Bridge.
Processors with CPUID signature of DisplayFamily_DisplayModel 06_2AH support performance events listed in
Table 19-16.
Vol. 3B 19-55
PERFORMANCE-MONITORING EVENTS
Table 19-16. Non-Architectural Performance Events In the Processor Uncore for 2nd Generation
Intel® Core™ i7-2xxx, Intel® Core™ i5-2xxx, Intel® Core™ i3-2xxx Processor Series
Event
Num.1
Umask
Value
22H
01H
UNC_CBO_XSNP_RESPONSE.M A snoop misses in some processor core.
ISS
22H
02H
UNC_CBO_XSNP_RESPONSE.I
NVAL
22H
04H
UNC_CBO_XSNP_RESPONSE.H A snoop hits a non-modified line in some processor
IT
core.
22H
08H
UNC_CBO_XSNP_RESPONSE.H A snoop hits a modified line in some processor core.
ITM
22H
10H
UNC_CBO_XSNP_RESPONSE.I
NVAL_M
A snoop invalidates a modified line in some processor
core.
22H
20H
UNC_CBO_XSNP_RESPONSE.E
XTERNAL_FILTER
Filter on cross-core snoops initiated by this Cbox due
to external snoop request.
22H
40H
UNC_CBO_XSNP_RESPONSE.X Filter on cross-core snoops initiated by this Cbox due
CORE_FILTER
to processor core memory request.
22H
80H
UNC_CBO_XSNP_RESPONSE.E
VICTION_FILTER
Filter on cross-core snoops initiated by this Cbox due
to LLC eviction.
34H
01H
UNC_CBO_CACHE_LOOKUP.M
34H
02H
UNC_CBO_CACHE_LOOKUP.E
LLC lookup request that access cache and found line in Must combine with
M-state.
one of the umask
LLC lookup request that access cache and found line in values of 10H, 20H,
40H, 80H.
E-state.
34H
04H
UNC_CBO_CACHE_LOOKUP.S
LLC lookup request that access cache and found line in
S-state.
34H
08H
UNC_CBO_CACHE_LOOKUP.I
LLC lookup request that access cache and found line in
I-state.
34H
10H
UNC_CBO_CACHE_LOOKUP.RE
AD_FILTER
Filter on processor core initiated cacheable read
requests. Must combine with at least one of 01H, 02H,
04H, 08H.
34H
20H
UNC_CBO_CACHE_LOOKUP.WR Filter on processor core initiated cacheable write
ITE_FILTER
requests. Must combine with at least one of 01H, 02H,
04H, 08H.
34H
40H
UNC_CBO_CACHE_LOOKUP.EX
TSNP_FILTER
34H
80H
UNC_CBO_CACHE_LOOKUP.AN Filter on any IRQ or IPQ initiated requests including
Y_REQUEST_FILTER
uncacheable, non-coherent requests. Must combine
with at least one of 01H, 02H, 04H, 08H.
80H
01H
UNC_ARB_TRK_OCCUPANCY.A Counts cycles weighted by the number of requests
Counter 0 only.
LL
waiting for data returning from the memory controller.
Accounts for coherent and non-coherent requests
initiated by IA cores, processor graphic units, or LLC.
81H
01H
UNC_ARB_TRK_REQUEST.ALL
Counts the number of coherent and in-coherent
requests initiated by IA cores, processor graphic units,
or LLC.
81H
20H
UNC_ARB_TRK_REQUEST.WRI
TES
Counts the number of allocated write entries, include
full, partial, and LLC evictions.
81H
80H
UNC_ARB_TRK_REQUEST.EVIC Counts the number of LLC evictions allocated.
TIONS
19-56 Vol. 3B
Event Mask Mnemonic
Description
A snoop invalidates a non-modified line in some
processor core.
Comment
Must combine with
one of the umask
values of 20H, 40H,
80H.
Must combine with at
least one of 01H, 02H,
04H, 08H, 10H.
Filter on external snoop requests. Must combine with
at least one of 01H, 02H, 04H, 08H.
PERFORMANCE-MONITORING EVENTS
Table 19-16. Non-Architectural Performance Events In the Processor Uncore for 2nd Generation
Intel® Core™ i7-2xxx, Intel® Core™ i5-2xxx, Intel® Core™ i3-2xxx Processor Series (Contd.)
Event
Num.1
Umask
Value
Event Mask Mnemonic
Description
Comment
83H
01H
UNC_ARB_COH_TRK_OCCUPA
NCY.ALL
Cycles weighted by number of requests pending in
Coherency Tracker.
Counter 0 only.
84H
01H
UNC_ARB_COH_TRK_REQUES
T.ALL
Number of requests allocated in Coherency Tracker.
NOTES:
1. The uncore events must be programmed using MSRs located in specific performance monitoring units in the uncore. UNC_CBO*
events are supported using MSR_UNC_CBO* MSRs; UNC_ARB* events are supported using MSR_UNC_ARB*MSRs.
19.7
PERFORMANCE MONITORING EVENTS FOR INTEL® CORE™ I7 PROCESSOR
FAMILY AND INTEL® XEON® PROCESSOR FAMILY
Processors based on the Intel microarchitecture code name Nehalem support the architectural and non-architectural performance-monitoring events listed in Table 19-1 and Table 19-17. The events in Table 19-17 generally
applies to processors with CPUID signature of DisplayFamily_DisplayModel encoding with the following values:
06_1AH, 06_1EH, 06_1FH, and 06_2EH. However, Intel Xeon processors with CPUID signature of
DisplayFamily_DisplayModel 06_2EH have a small number of events that are not supported in processors with
CPUID signature 06_1AH, 06_1EH, and 06_1FH. These events are noted in the comment column.
In addition, these processors (CPUID signature of DisplayFamily_DisplayModel 06_1AH, 06_1EH, 06_1FH) also
support the following non-architectural, product-specific uncore performance-monitoring events listed in Table
19-18.
Fixed counters in the core PMU support the architecture events defined in Table 19-2.
Table 19-17. Non-Architectural Performance Events In the Processor Core for
Intel® Core™ i7 Processor and Intel® Xeon® Processor 5500 Series
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
04H
07H
SB_DRAIN.ANY
Counts the number of store buffer drains.
06H
04H
STORE_BLOCKS.AT_RET
Counts number of loads delayed with at-Retirement
block code. The following loads need to be executed
at retirement and wait for all senior stores on the
same thread to be drained: load splitting across 4K
boundary (page split), load accessing uncacheable
(UC or WC) memory, load lock, and load with page
table in UC or WC memory region.
06H
08H
STORE_BLOCKS.L1D_BLOCK
Cacheable loads delayed with L1D block code.
07H
01H
PARTIAL_ADDRESS_ALIAS
Counts false dependency due to partial address
aliasing.
Counts all load misses that cause a page walk.
08H
01H
DTLB_LOAD_MISSES.ANY
08H
02H
DTLB_LOAD_MISSES.WALK_CO Counts number of completed page walks due to load
MPLETED
miss in the STLB.
08H
10H
DTLB_LOAD_MISSES.STLB_HIT Number of cache load STLB hits.
08H
20H
DTLB_LOAD_MISSES.PDE_MIS
S
08H
80H
DTLB_LOAD_MISSES.LARGE_W Counts number of completed large page walks due
ALK_COMPLETED
to load miss in the STLB.
Comment
Number of DTLB cache load misses where the low
part of the linear to physical address translation
was missed.
Vol. 3B 19-57
PERFORMANCE-MONITORING EVENTS
Table 19-17. Non-Architectural Performance Events In the Processor Core for
Intel® Core™ i7 Processor and Intel® Xeon® Processor 5500 Series (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
0BH
01H
MEM_INST_RETIRED.LOADS
Counts the number of instructions with an
architecturally-visible load retired on the
architected path.
0BH
02H
MEM_INST_RETIRED.STORES
Counts the number of instructions with an
architecturally-visible store retired on the
architected path.
0BH
10H
MEM_INST_RETIRED.LATENCY
_ABOVE_THRESHOLD
Counts the number of instructions exceeding the
latency specified with ld_lat facility.
0CH
01H
MEM_STORE_RETIRED.DTLB_
MISS
The event counts the number of retired stores that
missed the DTLB. The DTLB miss is not counted if
the store operation causes a fault. Does not counter
prefetches. Counts both primary and secondary
misses to the TLB.
0EH
01H
UOPS_ISSUED.ANY
Counts the number of Uops issued by the Register
Allocation Table to the Reservation Station, i.e. the
UOPs issued from the front end to the back end.
0EH
01H
UOPS_ISSUED.STALLED_CYCLE Counts the number of cycles no Uops issued by the Set “invert=1, cmask =
S
Register Allocation Table to the Reservation
1“.
Station, i.e. the UOPs issued from the front end to
the back end.
0EH
02H
UOPS_ISSUED.FUSED
Counts the number of fused Uops that were issued
from the Register Allocation Table to the
Reservation Station.
0FH
01H
MEM_UNCORE_RETIRED.L3_D
ATA_MISS_UNKNOWN
Counts number of memory load instructions retired Available only for CPUID
where the memory reference missed L3 and data
signature 06_2EH.
source is unknown.
0FH
02H
MEM_UNCORE_RETIRED.OTHE Counts number of memory load instructions retired
R_CORE_L2_HITM
where the memory reference hit modified data in a
sibling core residing on the same socket.
0FH
08H
MEM_UNCORE_RETIRED.REMO Counts number of memory load instructions retired
TE_CACHE_LOCAL_HOME_HIT where the memory reference missed the L1, L2 and
L3 caches and HIT in a remote socket's cache. Only
counts locally homed lines.
0FH
10H
MEM_UNCORE_RETIRED.REMO Counts number of memory load instructions retired
TE_DRAM
where the memory reference missed the L1, L2 and
L3 caches and was remotely homed. This includes
both DRAM access and HITM in a remote socket's
cache for remotely homed lines.
0FH
20H
MEM_UNCORE_RETIRED.LOCA
L_DRAM
0FH
80H
MEM_UNCORE_RETIRED.UNCA Counts number of memory load instructions retired Available only for CPUID
CHEABLE
where the memory reference missed the L1, L2 and signature 06_2EH.
L3 caches and to perform I/O.
19-58 Vol. 3B
Comment
In conjunction with ld_lat
facility.
Counts number of memory load instructions retired
where the memory reference missed the L1, L2 and
L3 caches and required a local socket memory
reference. This includes locally homed cachelines
that were in a modified state in another socket.
PERFORMANCE-MONITORING EVENTS
Table 19-17. Non-Architectural Performance Events In the Processor Core for
Intel® Core™ i7 Processor and Intel® Xeon® Processor 5500 Series (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
10H
01H
FP_COMP_OPS_EXE.X87
Counts the number of FP Computational Uops
Executed. The number of FADD, FSUB, FCOM,
FMULs, integer MULs and IMULs, FDIVs, FPREMs,
FSQRTS, integer DIVs, and IDIVs. This event does
not distinguish an FADD used in the middle of a
transcendental flow from a separate FADD
instruction.
10H
02H
FP_COMP_OPS_EXE.MMX
Counts number of MMX Uops executed.
10H
04H
FP_COMP_OPS_EXE.SSE_FP
Counts number of SSE and SSE2 FP uops executed.
10H
08H
FP_COMP_OPS_EXE.SSE2_INT Counts number of SSE2 integer uops executed.
EGER
10H
10H
FP_COMP_OPS_EXE.SSE_FP_P Counts number of SSE FP packed uops executed.
ACKED
10H
20H
FP_COMP_OPS_EXE.SSE_FP_S Counts number of SSE FP scalar uops executed.
CALAR
10H
40H
FP_COMP_OPS_EXE.SSE_SING Counts number of SSE* FP single precision uops
LE_PRECISION
executed.
10H
80H
FP_COMP_OPS_EXE.SSE_DOU
BLE_PRECISION
Counts number of SSE* FP double precision uops
executed.
12H
01H
SIMD_INT_128.PACKED_MPY
Counts number of 128 bit SIMD integer multiply
operations.
12H
02H
SIMD_INT_128.PACKED_SHIFT Counts number of 128 bit SIMD integer shift
operations.
12H
04H
SIMD_INT_128.PACK
Counts number of 128 bit SIMD integer pack
operations.
12H
08H
SIMD_INT_128.UNPACK
Counts number of 128 bit SIMD integer unpack
operations.
12H
10H
SIMD_INT_128.PACKED_LOGIC Counts number of 128 bit SIMD integer logical
AL
operations.
12H
20H
SIMD_INT_128.PACKED_ARITH Counts number of 128 bit SIMD integer arithmetic
operations.
12H
40H
SIMD_INT_128.SHUFFLE_MOV Counts number of 128 bit SIMD integer shuffle and
E
move operations.
13H
01H
LOAD_DISPATCH.RS
Counts number of loads dispatched from the
Reservation Station that bypass the Memory Order
Buffer.
13H
02H
LOAD_DISPATCH.RS_DELAYED
Counts the number of delayed RS dispatches at the
stage latch. If an RS dispatch can not bypass to LB,
it has another chance to dispatch from the onecycle delayed staging latch before it is written into
the LB.
13H
04H
LOAD_DISPATCH.MOB
Counts the number of loads dispatched from the
Reservation Station to the Memory Order Buffer.
13H
07H
LOAD_DISPATCH.ANY
Counts all loads dispatched from the Reservation
Station.
Comment
Vol. 3B 19-59
PERFORMANCE-MONITORING EVENTS
Table 19-17. Non-Architectural Performance Events In the Processor Core for
Intel® Core™ i7 Processor and Intel® Xeon® Processor 5500 Series (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
Comment
14H
01H
ARITH.CYCLES_DIV_BUSY
Counts the number of cycles the divider is busy
executing divide or square root operations. The
divide can be integer, X87 or Streaming SIMD
Extensions (SSE). The square root operation can be
either X87 or SSE.
Count may be incorrect
When SMT is on.
Set 'edge =1, invert=1, cmask=1' to count the
number of divides.
14H
02H
ARITH.MUL
Counts the number of multiply operations executed. Count may be incorrect
This includes integer as well as floating point
When SMT is on.
multiply operations but excludes DPPS mul and
MPSAD.
17H
01H
INST_QUEUE_WRITES
Counts the number of instructions written into the
instruction queue every cycle.
18H
01H
INST_DECODED.DEC0
Counts number of instructions that require decoder
0 to be decoded. Usually, this means that the
instruction maps to more than 1 uop.
19H
01H
TWO_UOP_INSTS_DECODED
An instruction that generates two uops was
decoded.
1EH
01H
INST_QUEUE_WRITE_CYCLES
This event counts the number of cycles during
which instructions are written to the instruction
queue. Dividing this counter by the number of
instructions written to the instruction queue
(INST_QUEUE_WRITES) yields the average number
of instructions decoded each cycle. If this number is
less than four and the pipe stalls, this indicates that
the decoder is failing to decode enough instructions
per cycle to sustain the 4-wide pipeline.
20H
01H
LSD_OVERFLOW
Counts number of loops that can’t stream from the
instruction queue.
24H
01H
L2_RQSTS.LD_HIT
Counts number of loads that hit the L2 cache. L2
loads include both L1D demand misses as well as
L1D prefetches. L2 loads can be rejected for various
reasons. Only non rejected loads are counted.
24H
02H
L2_RQSTS.LD_MISS
Counts the number of loads that miss the L2 cache.
L2 loads include both L1D demand misses as well as
L1D prefetches.
24H
03H
L2_RQSTS.LOADS
Counts all L2 load requests. L2 loads include both
L1D demand misses as well as L1D prefetches.
24H
04H
L2_RQSTS.RFO_HIT
Counts the number of store RFO requests that hit
the L2 cache. L2 RFO requests include both L1D
demand RFO misses as well as L1D RFO prefetches.
Count includes WC memory requests, where the
data is not fetched but the permission to write the
line is required.
24H
08H
L2_RQSTS.RFO_MISS
Counts the number of store RFO requests that miss
the L2 cache. L2 RFO requests include both L1D
demand RFO misses as well as L1D RFO prefetches.
19-60 Vol. 3B
If SSE* instructions that
are 6 bytes or longer
arrive one after another,
then front end
throughput may limit
execution speed.
PERFORMANCE-MONITORING EVENTS
Table 19-17. Non-Architectural Performance Events In the Processor Core for
Intel® Core™ i7 Processor and Intel® Xeon® Processor 5500 Series (Contd.)
Event
Num.
Umask
Value
Event Mask Mnemonic
Description
24H
0CH
L2_RQSTS.RFOS
Counts all L2 store RFO requests. L2 RFO requests
include both L1D demand RFO misses as well as
L1D RFO prefetches.
24H
10H
L2_RQSTS.IFETCH_HIT
Counts number of instruction fetches that hit the
L2 cache. L2 instruction fetches include both L1I
demand misses as well as L1I instruction
prefetches.
24H
20H
L2_RQSTS.IFETCH_MISS
Counts number of instruction fetches that miss the
L2 cache. L2 instruction fetches include both L1I
demand misses as well as L1I instruction
prefetches.
24H
30H
L2_RQSTS.IFETCHES
Counts all instruction fetches. L2 instruction fetches
include both L1I demand misses as well as L1I
instruction prefetches.
24H
40H
L2_RQSTS.PREFETCH_HIT
Counts L2 prefetch hits for both code and data.
24H
80H
L2_RQSTS.PREFETCH_MISS
Counts L2 prefetch misses for both code and data.
24H
C0H
L2_RQSTS.PREFETCHES
Counts all L2 prefetches for both code and data.
24H
AAH
L2_RQSTS.MISS
Counts all L2 misses for both code and data.
24H
FFH
L2_RQSTS.REFERENCES
Counts all L2 requests for both code and data.
26H
01H
L2_DATA_RQSTS.DEMAND.I_S
TATE
Counts number of L2 data demand loads where the
cache line to be loaded is in the I (invalid) state, i.e. a
cache miss. L2 demand loads are both L1D demand
misses and L1D prefetches.
26H
02H
L2_DATA_RQSTS.DEMAND.S_S Counts number of L2 data demand loads where the
TATE
cache line to be loaded is in the S (shared) state. L2
demand loads are both L1D demand misses and L1D
prefetches.
26H
04H
L2_DATA_RQSTS.DEMAND.E_S Counts number of L2 data demand loads where the
TATE
cache line to be loaded is in the E (exclusive) state.
L2 demand loads are both L1D demand misses and
L1D prefetches.
26H
08H
L2_DATA_RQSTS.DEMAND.M_
STATE
Counts number of L2 data demand loads where the
cache line to be loaded is in the M (modified) state.
L2 demand loads are both L1D demand misses and
L1D prefetches.
26H
0FH
L2_DATA_RQSTS.DEMAND.ME
SI
Counts all L2 data demand requests. L2 demand
loads are both L1D demand misses and L1D
prefetches.
26H
10H
L2_DATA_RQSTS.PREFETCH.I_ Counts number of L2 prefetch data loads where the
STATE
cache line to be loaded is in the I (invalid) state, i.e. a
cache miss.
26H
20H
L2_DATA_RQSTS.PREFETCH.S
_STATE
Counts number of L2 prefetch data loads where the
cache line to be loaded is in the S (shared) state. A
prefetch RFO will miss on an S state line, while a
prefetch read will hit on an S state line.
26H
40H
L2_DATA_RQSTS.PREFETCH.E
_STATE
Counts number of L2 prefetch data loads where the
cache line to be loaded is in the E (exclusive) state.
Comment
Vol. 3B 19-61
PERFORMANCE-MONITORING EVENTS
Table 19-17. Non-Architectural Performance Events In the Processor Core for
Intel® Core™ i7 Processor and Intel® Xeon® Processor 5500 Series (Contd.)
Event
Num.
Umask
Value
26H
80H
L2_DATA_RQSTS.PREFETCH.M Counts number of L2 prefetch data loads where the
_STATE
cache line to be loaded is in the M (modified) state.
26H
F0H
L2_DATA_RQSTS.PREFETCH.M Counts all L2 prefetch requests.
ESI
26H
FFH
L2_DATA_RQSTS.ANY
Counts all L2 data requests.
27H
01H
L2_WRITE.RFO.I_STATE
Counts number of L2 demand store RFO requests
This is a demand RFO
where the cache line to be loaded is in the I (invalid) request.
state, i.e, a cache miss. The L1D prefetcher does not
issue a RFO prefetch.
27H
02H
L2_WRITE.RFO.S_STATE
Counts number of L2 store RFO requests where the This is a demand RFO
cache line to be loaded is in the S (shared) state.
request.
The L1D prefetcher does not issue a RFO prefetch.
27H
08H
L2_WRITE.RFO.M_STATE
Counts number of L2 store RFO requests where the This is a demand RFO
cache line to be loaded is in the M (modified) state. request.
The L1D prefetcher does not issue a RFO prefetch.
27H
0EH
L2_WRITE.RFO.HIT
Counts number of L2 store RFO requests where the This is a demand RFO
cache line to be loaded is in either the S, E or M
request.
states. The L1D prefetcher does not issue a RFO
prefetch.
27H
0FH
L2_WRITE.RFO.MESI
Counts all L2 store RFO requests. The L1D
prefetcher does not issue a RFO prefetch.
27H
10H
L2_WRITE.LOCK.I_STATE
Counts number of L2 demand lock RFO requests
where the cache line to be loaded is in the I (invalid)
state, fo