[PATCH v2] admin guide/pm: Admin guide for intel-speed-select
From: Srinivas Pandruvada
Date: Tue Nov 19 2019 - 18:24:37 EST
Added documentation to configure servers to use Intel(R) Speed
Select Technology using intel-speed-select tool.
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>
Acked-by: Andriy Shevchenko <andy.shevchenko@xxxxxxxxx>
---
v2:
Only formatting changes. So used ACK from Andriy.
Addressed comments by Jonathan for the following items:
- Removed non ASCII character "Â"
- Addressed section/sub-section markers
- Folded all commands and outputs in literal blocks
.../admin-guide/pm/intel-speed-select.rst | 888 ++++++++++++++++++
.../admin-guide/pm/working-state.rst | 1 +
2 files changed, 889 insertions(+)
create mode 100644 Documentation/admin-guide/pm/intel-speed-select.rst
diff --git a/Documentation/admin-guide/pm/intel-speed-select.rst b/Documentation/admin-guide/pm/intel-speed-select.rst
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+.. SPDX-License-Identifier: GPL-2.0
+
+=========================================================
+Intel Speed Select Technology (Intel SST) : User Guide
+=========================================================
+
+The Intel Speed Select Technology (Intel SST) provides a powerful new
+collection of features that give more granular control over CPU performance.
+With Intel SST, one server can be configured for power and performance for a
+variety of diverse workload requirements.
+
+Refer to the links below for an overview of the technology:
+
+- https://www.intel.com/content/www/us/en/architecture-and-technology/speed-select-technology-article.html
+- https://builders.intel.com/docs/networkbuilders/intel-speed-select-technology-base-frequency-enhancing-performance.pdf
+
+These capabilities are further enhanced in some of the newer generations of
+server platforms where these features can be enumerated and controlled
+dynamically without pre-configuring via BIOS setup options. This dynamic
+configuration is done via mailbox commands to the hardware. One way to enumerate
+and configure these features is by using the Intel Speed Select utility.
+
+This document explains how to use the Intel Speed Select tool to enumerate and
+control Intel SST features. This document gives example commands and explains
+how these commands change the power and performance profile of the system under
+test. Using this tool as an example, customers can replicate the messaging
+implemented in the tool in their production software.
+
+intel-speed-select configuration tool
+======================================
+
+Most Linux distribution packages may include the "intel-speed-select" tool. If not,
+it can be built by downloading the Linux kernel tree from kernel.org. Once
+downloaded, the tool can be built without building the full kernel.
+
+From the kernel tree, run the following commands::
+
+# cd tools/power/x86/intel-speed-select/
+# make
+# make install
+
+Getting Help
+------------
+
+To get help with the tool, execute the command below::
+
+# intel-speed-select --help
+
+The top-level help describes arguments and features. Notice that there is a
+multi-level help structure in the tool. For example, to get help for the feature "perf-profile"::
+
+# intel-speed-select perf-profile --help
+
+To get help on a command, another level of help is provided. For example for the command info "info"::
+
+# intel-speed-select perf-profile info --help
+
+Intel Speed Select Technology - Performance Profile (Intel SST-PP)
+-------------------------------------------------------------------
+
+This feature allows configuration of a server dynamically based on workload
+performance requirements. This helps users during deployment as they do not have
+to choose a specific server configuration statically. This Intel Speed Select
+Technology - Performance Profile (Intel SST-PP) feature introduces a mechanism
+that allows multiple optimized performance profiles per system. Each profile
+defines a set of CPUs that need to be online and rest offline to sustain a
+guaranteed base frequency. Once the user issues a command to use a specific
+performance profile and meet CPU online/offline requirement, the user can expect
+a change in the base frequency dynamically. This feature is called
+"perf-profile" when using the Intel Speed Select tool.
+
+Number or performance levels
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+There can be multiple performance profiles on a system. To get the number of
+profiles, execute the command below::
+
+ # intel-speed-select perf-profile get-config-levels
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ package-0
+ die-0
+ cpu-0
+ get-config-levels:4
+ package-1
+ die-0
+ cpu-14
+ get-config-levels:4
+
+On this system under test, there are 4 performance profiles in addition to the
+base performance profile (which is performance level 0).
+
+Lock/Unlock status
+~~~~~~~~~~~~~~~~~~
+
+Even if there are multiple performance profiles, it is possible that that they
+are locked. If they are locked, users cannot issue a command to change the
+performance state. It is possible that there is a BIOS setup to unlock or check
+with your system vendor.
+
+To check if the system is locked, execute the following command::
+
+ # intel-speed-select perf-profile get-lock-status
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ package-0
+ die-0
+ cpu-0
+ get-lock-status:0
+ package-1
+ die-0
+ cpu-14
+ get-lock-status:0
+
+In this case, lock status is 0, which means that the system is unlocked.
+
+Properties of a performance level
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To get properties of a specific performance level (For example for the level 0, below), execute the command below::
+
+ # intel-speed-select perf-profile info -l 0
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ package-0
+ die-0
+ cpu-0
+ perf-profile-level-0
+ cpu-count:28
+ enable-cpu-mask:000003ff,f0003fff
+ enable-cpu-list:0,1,2,3,4,5,6,7,8,9,10,11,12,13,28,29,30,31,32,33,34,35,36,37,38,39,40,41
+ thermal-design-power-ratio:26
+ base-frequency(MHz):2600
+ speed-select-turbo-freq:disabled
+ speed-select-base-freq:disabled
+ ...
+ ...
+
+Here -l option is used to specify a performance level.
+
+If the option -l is omitted, then this command will print information about all
+the performance levels. The above command is printing properties of the
+performance level 0.
+
+For this performance profile, the list of CPUs displayed by the
+"enable-cpu-mask/enable-cpu-list" at the max can be "online." When that
+condition is met, then base frequency of 2600 MHz can be maintained. To
+understand more, execute "intel-speed-select perf-profile info" for performance
+level 4::
+
+ # intel-speed-select perf-profile info -l 4
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ package-0
+ die-0
+ cpu-0
+ perf-profile-level-4
+ cpu-count:28
+ enable-cpu-mask:000000fa,f0000faf
+ enable-cpu-list:0,1,2,3,5,7,8,9,10,11,28,29,30,31,33,35,36,37,38,39
+ thermal-design-power-ratio:28
+ base-frequency(MHz):2800
+ speed-select-turbo-freq:disabled
+ speed-select-base-freq:unsupported
+ ...
+ ...
+
+There are fewer CPUs in the âenable-cpu-mask/enable-cpu-list.â Consequently, if
+the user only keeps these CPUs online and the rest "offline," then the base
+frequency is increased to 2.8 GHz compared to 2.6 GHz at performance level 0.
+
+Get current performance level
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To get the current performance level, execute::
+
+ # intel-speed-select perf-profile get-config-current-level
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ package-0
+ die-0
+ cpu-0
+ get-config-current_level:0
+
+First verify that the base_frequency displayed by the cpufreq sysfs is correct::
+
+ # cat /sys/devices/system/cpu/cpu0/cpufreq/base_frequency
+ 2600000
+
+This matches the base-frequency (MHz) field value displayed from the
+"perf-profile info" command for performance level 0(cpufreq frequency is in
+KHz).
+
+To check if the average frequency is equal to the base frequency for a 100% busy
+workload, disable turbo::
+
+# echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo
+
+Then runs a busy workload on all CPUs, for example::
+
+#stress -c 64
+
+To verify the base frequency, run turbostat::
+
+ #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1
+
+ Package Core CPU Bzy_MHz
+ - - 2600
+ 0 0 0 2600
+ 0 1 1 2600
+ 0 2 2 2600
+ 0 3 3 2600
+ 0 4 4 2600
+ . . . .
+
+
+Changing performance level
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To the change the performance level to 4, execute::
+
+ # intel-speed-select -d perf-profile set-config-level -l 4 -o
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ package-0
+ die-0
+ cpu-0
+ perf-profile
+ set_tdp_level:success
+
+In the command above, "-o" is optional. If it is specified, then it will also
+offline CPUs which are not present in the enable_cpu_mask for this performance
+level.
+
+Now if the base_frequency is checked::
+
+ #cat /sys/devices/system/cpu/cpu0/cpufreq/base_frequency
+ 2800000
+
+Which shows that the base frequency now increased from 2600 MHz at performance
+level 0 to 2800 MHz at performance level 4. As a result, any workload, which can
+use fewer CPUs, can see a boost of 200 MHz compared to performance level 0.
+
+Check presence of other Intel SST features
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Each of the performance profiles also specifies weather there is support of
+other two Intel SST features (Intel Speed Select Technology - Base Frequency
+(Intel SST-BF) and Intel Speed Select Technology - Turbo Frequency (Intel
+SST-TF)).
+
+For example, from the output of "perf-profile info" above, for level 0 and level
+4:
+
+For level 0::
+ speed-select-turbo-freq:disabled
+ speed-select-base-freq:disabled
+
+For level 4::
+ speed-select-turbo-freq:disabled
+ speed-select-base-freq:unsupported
+
+Given these results, the âspeed-select-base-freqâ (Intel SST-BF) in level 4
+changed from "disabled" to "unsupported" compared to performance level 0.
+
+This means that at performance level 4, the "speed-select-base-freq" feature is
+not supported. However, at performance level 0, this feature is "supported", but
+currently "disabled", meaning the user has not activated this feature. Whereas
+"speed-select-turbo-freq" (Intel SST-TF) is supported at both performance
+levels, but currently not activated by the user.
+
+The Intel SST-BF and the Intel SST-TF features are built on a foundation
+technology called Intel Speed Select Technology - Core Power (Intel SST-CP).
+The platform firmware enables this feature when Intel SST-BF or Intel SST-TF
+is supported on a platform.
+
+Intel Speed Select Technology â Core Power (Intel SST-CP)
+----------------------------------------------------------
+
+Intel Speed Select Technology â Core Power (Intel SST-CP) is an interface that
+allows users to define per core priority. This defines a mechanism to distribute
+power among cores when there is a power constrained scenario. This defines a
+class of service (CLOS) configuration.
+
+The user can configure up to 4 class of service configurations. Each CLOS group
+configuration allows definitions of parameters, which affects how the frequency
+can be limited and power is distributed. Each CPU core can be tied to a class of
+service and hence an associated priority. The granularity is at core level not
+at per CPU level.
+
+Enable CLOS based prioritization
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To use CLOS based prioritization feature, firmware must be informed to enable
+and use a priority type. There is a default per platform priority type, which
+can be changed with optional command line parameter.
+
+To enable and check the options, execute::
+
+ # intel-speed-select core-power enable --help
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ Enable core-power for a package/die
+ Clos Enable: Specify priority type with [--priority|-p]
+ 0: Proportional, 1: Ordered
+
+There are two types of priority types:
+
+- Ordered
+
+Priority for ordered throttling is defined based on the index of the assigned
+CLOS group. Where CLOS0 gets highest priority (throttled last).
+
+Priority order is:
+CLOS0 > CLOS1 > CLOS2 > CLOS3.
+
+- Proportional
+
+When proportional priority is used, there is an additional parameter called
+frequency_weight, which can be specified per CLOS group. The goal of
+proportional priority is to provide each core with the requested min., then
+distribute all remaining (excess/deficit) budgets in proportion to a defined
+weight. This proportional priority can be configured using "core-power config"
+command.
+
+To enable with the platform default priority type, execute::
+
+ # intel-speed-select core-power enable
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ package-0
+ die-0
+ cpu-0
+ core-power
+ enable:success
+ package-1
+ die-0
+ cpu-6
+ core-power
+ enable:success
+
+The scope of this enable is per package or die scoped when a package contains
+multiple dies. To check if CLOS is enabled and get priority type, "core-power
+info" command can be used. For example to check the status of core-power feature
+on CPU 0, execute::
+
+ # intel-speed-select -c 0 core-power info
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ package-0
+ die-0
+ cpu-0
+ core-power
+ enable-status:1
+ priority-type:0
+
+
+Configuring CLOS groups
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Each CLOS group has its own attributes including min, max, freq_weight and
+desired. These parameters can be configured with "core-power config" command.
+Defaults will be used if user skips setting a parameter except clos id, which is
+mandatory. To check core-power config options, execute::
+
+ # intel-speed-select core-power config --help
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ Set core-power configuration for one of the four clos ids
+ Specify targeted clos id with [--clos|-c]
+ Specify clos Proportional Priority [--weight|-w]
+ Specify clos min in MHz with [--min|-n]
+ Specify clos max in MHz with [--max|-m]
+ Specify clos desired in MHz with [--desired|-d]
+
+For example::
+
+ # intel-speed-select core-power config -c 0
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ clos epp is not specified, default: 0
+ clos frequency weight is not specified, default: 0
+ clos min is not specified, default: 0 MHz
+ clos max is not specified, default: 25500 MHz
+ clos desired is not specified, default: 0
+ package-0
+ die-0
+ cpu-0
+ core-power
+ config:success
+ package-1
+ die-0
+ cpu-6
+ core-power
+ config:success
+
+The user has the option to change defaults. For example, the user can change the
+"min" and set the base frequency to always get guaranteed base frequency.
+
+Get the current CLOS configuration
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To check the current configuration, "core-power get-config" can be used. For
+example, to get the configuration of CLOS 0::
+
+ # intel-speed-select core-power get-config -c 0
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ package-0
+ die-0
+ cpu-0
+ core-power
+ clos:0
+ epp:0
+ clos-proportional-priority:0
+ clos-min:0 MHz
+ clos-max:25500 MHz
+ clos-desired:0
+ package-1
+ die-0
+ cpu-6
+ core-power
+ clos:0
+ epp:0
+ clos-proportional-priority:0
+ clos-min:0 MHz
+ clos-max:25500 MHz
+ clos-desired:0
+
+Associating a CPU with a CLOS group
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To associate a CPU to a CLOS group "core-power assoc" command can be used::
+
+ # intel-speed-select core-power assoc --help
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ Associate a clos id to a CPU
+ Specify targeted clos id with [--clos|-c]
+
+
+For example to associate CPU 10 to CLOS group 3, execute::
+
+ # intel-speed-select -c 10 core-power assoc -c 3
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ package-0
+ die-0
+ cpu-10
+ core-power
+ assoc:success
+
+Once a CPU is associated, its sibling CPUs are also associated to a CLOS group.
+Once associated, avoid changing Linux âcpufreqâ subsystem scaling frequency
+limits.
+
+To check the existing association for a CPU, "core-power get-assoc" command can
+be used. For example, to get association of CPU 10, execute::
+
+ # intel-speed-select -c 10 core-power get-assoc
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ package-1
+ die-0
+ cpu-10
+ get-assoc
+ clos:3
+
+This shows that CPU 10 is part of a CLOS group 3.
+
+
+Disable CLOS based prioritization
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To disable, execute::
+
+# intel-speed-select core-power disable
+
+Some features like Intel SST-TF can only be enabled when CLOS based prioritization
+is enabled. For this reason, disabling while Intel SST-TF is enabled can cause
+Intel SST-TF to fail. This will cause the "disable" command to display an error
+if Intel SST-TF is already enabled. In turn, to disable, the Intel SST-TF
+feature must be disabled first.
+
+Intel Speed Select Technology - Base Frequency (Intel SST-BF)
+---------------------------------------------------------------
+
+The Intel Speed Select Technology - Base Frequency (Intel SST-BF) feature lets
+the user control base frequency. If some critical workload threads demand
+constant high guaranteed performance, then this feature can be used to execute
+the thread at higher base frequency on specific sets of CPUs (high priority
+CPUs) at the cost of lower base frequency (low priority CPUs) on other CPUs.
+This feature does not require offline of the low priority CPUs.
+
+The support of Intel SST-BF depends on the Intel Speed Select Technology -
+Performance Profile (Intel SST-PP) performance level configuration. It is
+possible that only certain performance levels support Intel SST-BF. It is also
+possible that only base performance level (level = 0) has support of Intel
+SST-BF. Consequently, first select the desired performance level to enable this
+feature.
+
+In the system under test here, Intel SST-BF is supported at the base
+performance level 0, but currently disabled. For example for the level 0::
+
+ # intel-speed-select -c 0 perf-profile info -l 0
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ package-0
+ die-0
+ cpu-0
+ perf-profile-level-0
+ ...
+
+ speed-select-base-freq:disabled
+ ...
+
+Before enabling Intel SST-BF and measuring its impact on a workload
+performance, execute some workload and measure performance and get a baseline
+performance to compare against.
+
+Here the user wants more guaranteed performance. For this reason, it is likely
+that turbo is disabled. To disable turbo, execute::
+
+#echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo
+
+Based on the output of the "intel-speed-select perf-profile info -l 0" base
+frequency of guaranteed frequency 2600 MHz.
+
+
+Measure baseline performance for comparison
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To compare, pick a multi-threaded workload where each thread can be scheduled on
+separate CPUs. "Hackbench pipe" test is a good example on how to improve
+performance using Intel SST-BF.
+
+Below, the workload is measuring average scheduler wakeup latency, so a lower
+number means better performance::
+
+ # taskset -c 3,4 perf bench -r 100 sched pipe
+ # Running 'sched/pipe' benchmark:
+ # Executed 1000000 pipe operations between two processes
+ Total time: 6.102 [sec]
+ 6.102445 usecs/op
+ 163868 ops/sec
+
+While running the above test, if we take turbostat output, it will show us that
+2 of the CPUs are busy and reaching max. frequency (which would be the base
+frequency as the turbo is disabled). The turbostat output::
+
+ #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1
+ Package Core CPU Bzy_MHz
+ 0 0 0 1000
+ 0 1 1 1005
+ 0 2 2 1000
+ 0 3 3 2600
+ 0 4 4 2600
+ 0 5 5 1000
+ 0 6 6 1000
+ 0 7 7 1005
+ 0 8 8 1005
+ 0 9 9 1000
+ 0 10 10 1000
+ 0 11 11 995
+ 0 12 12 1000
+ 0 13 13 1000
+
+From the above turbostat output, both CPU 3 and 4 are very busy and reaching
+full guaranteed frequency of 2600 MHz.
+
+Intel SST-BF Capabilities
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To get capabilities of Intel SST-BF for the current performance level 0,
+execute::
+
+ # intel-speed-select base-freq info -l 0
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ package-0
+ die-0
+ cpu-0
+ speed-select-base-freq
+ high-priority-base-frequency(MHz):3000
+ high-priority-cpu-mask:00000216,00002160
+ high-priority-cpu-list:5,6,8,13,33,34,36,41
+ low-priority-base-frequency(MHz):2400
+ tjunction-temperature(C):125
+ thermal-design-power(W):205
+
+The above capabilities show that there are some CPUs on this system that can
+offer base frequency of 3000 MHz compared to the standard base frequency at this
+performance levels. Nevertheless, these CPUs are fixed, and they are presented
+via high-priority-cpu-list/high-priority-cpu-mask. But if this Intel SST-BF
+feature is selected, the low priorities CPUs (which are not in
+high-priority-cpu-list) can only offer up to 2400 MHz. As a result, if this
+clipping of low priority CPUs is acceptable, then the user can enable Intel
+SST-BF feature particularly for the above "sched pipe" workload since only two
+CPUs are used, they can be scheduled on high priority CPUs and can get boost of
+400 MHz.
+
+Enable Intel SST-BF
+~~~~~~~~~~~~~~~~~~~
+
+To enable Intel SST-BF feature, execute::
+
+ # intel-speed-select base-freq enable -a
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ package-0
+ die-0
+ cpu-0
+ base-freq
+ enable:success
+ package-1
+ die-0
+ cpu-14
+ base-freq
+ enable:success
+
+In this case, -a option is optional. This not only enables Intel SST-BF, but it
+also adjusts the priority of cores using Intel Speed Select Technology â Core
+Power (Intel SST-CP) features. This option sets the minimum performance of each
+Intel Speed Select Technology - Performance Profile (Intel SST-PP) class to
+maximum performance so that the hardware will give maximum performance possible
+for each CPU.
+
+If -a option is not used, then the following steps are required before enabling
+Intel SST-BF:
+
+- Discover Intel SST-BF and note low and high priority base frequency
+- Note the high prioity CPU list
+- Enable CLOS using core-power feature set
+- Configure CLOS parameters. Use CLOS.min to set to minimum performance
+- Subscribe desired CPUs to CLOS groups
+
+With this configuration, if the same workload is executed by pinning the
+workload to high priority CPUs (CPU 5 and 6 in this case)::
+
+ #taskset -c 5,6 perf bench -r 100 sched pipe
+ # Running 'sched/pipe' benchmark:
+ # Executed 1000000 pipe operations between two processes
+ Total time: 5.627 [sec]
+ 5.627922 usecs/op
+ 177685 ops/sec
+
+This way, by enabling Intel SST-BF, the performance of this benchmark is
+improved (latency reduced) by 7.79%. From the turbostat output, it can be
+observed that the high priority CPUs reached 3000 MHz compared to 2600 MHz.
+The turbostat output::
+
+ #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1
+ Package Core CPU Bzy_MHz
+ 0 0 0 2151
+ 0 1 1 2166
+ 0 2 2 2175
+ 0 3 3 2175
+ 0 4 4 2175
+ 0 5 5 3000
+ 0 6 6 3000
+ 0 7 7 2180
+ 0 8 8 2662
+ 0 9 9 2176
+ 0 10 10 2175
+ 0 11 11 2176
+ 0 12 12 2176
+ 0 13 13 2661
+
+Disable Intel SST-BF
+~~~~~~~~~~~~~~~~~~~~
+
+To disable the Intel SST-BF feature, execute::
+
+# intel-speed-select base-freq disable -a
+
+
+Intel Speed Select Technology - Turbo Frequency (Intel SST-TF)
+--------------------------------------------------------------
+
+This feature enables the ability to set different "All core turbo ratio limits"
+to cores based on the priority. By using this feature, some cores can be
+configured to get higher turbo frequency by designating them as high priority at
+the cost of lower or no turbo frequency on the low priority cores.
+
+For this reason, this feature is only useful when system is busy utilizing all
+CPUs, but the user wants some configurable option to get high performance on
+some CPUs.
+
+The support of Intel Speed Select Technology - Turbo Frequency (Intel SST-TF)
+depends on the Intel Speed Select Technology - Performance Profile (Intel
+SST-PP) performance level configuration. It is possible that only a certain
+performance level supports Intel SST-TF. It is also possible that only the base
+performance level (level = 0) has the support of Intel SST-TF. Hence, first
+select the desired performance level to enable this feature.
+
+In the system under test here, Intel SST-TF is supported at the base
+performance level 0, but currently disabled::
+
+ # intel-speed-select -c 0 perf-profile info -l 0
+ Intel(R) Speed Select Technology
+ package-0
+ die-0
+ cpu-0
+ perf-profile-level-0
+ ...
+ ...
+ speed-select-turbo-freq:disabled
+ ...
+ ...
+
+
+To check if performance can be improved using Intel SST-TF feature, get the turbo
+frequency properties with Intel SST-TF enabled and compare to the base turbo
+capability of this system.
+
+Get Base turbo capability
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To get the base turbo capability of performance level 0, execute::
+
+ # intel-speed-select perf-profile info -l 0
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ package-0
+ die-0
+ cpu-0
+ perf-profile-level-0
+ ...
+ ...
+ turbo-ratio-limits-sse
+ bucket-0
+ core-count:2
+ max-turbo-frequency(MHz):3200
+ bucket-1
+ core-count:4
+ max-turbo-frequency(MHz):3100
+ bucket-2
+ core-count:6
+ max-turbo-frequency(MHz):3100
+ bucket-3
+ core-count:8
+ max-turbo-frequency(MHz):3100
+ bucket-4
+ core-count:10
+ max-turbo-frequency(MHz):3100
+ bucket-5
+ core-count:12
+ max-turbo-frequency(MHz):3100
+ bucket-6
+ core-count:14
+ max-turbo-frequency(MHz):3100
+ bucket-7
+ core-count:16
+ max-turbo-frequency(MHz):3100
+
+Based on the data above, when all the CPUS are busy, the max. frequency of 3100
+MHz can be achieved. If there is some busy workload on cpu 0 - 11 (e.g. stress)
+and on CPU 12 and 13, execute "hackbench pipe" workload::
+
+ # taskset -c 12,13 perf bench -r 100 sched pipe
+ # Running 'sched/pipe' benchmark:
+ # Executed 1000000 pipe operations between two processes
+ Total time: 5.705 [sec]
+ 5.705488 usecs/op
+ 175269 ops/sec
+
+The turbostat output::
+
+ #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1
+ Package Core CPU Bzy_MHz
+ 0 0 0 3000
+ 0 1 1 3000
+ 0 2 2 3000
+ 0 3 3 3000
+ 0 4 4 3000
+ 0 5 5 3100
+ 0 6 6 3100
+ 0 7 7 3000
+ 0 8 8 3100
+ 0 9 9 3000
+ 0 10 10 3000
+ 0 11 11 3000
+ 0 12 12 3100
+ 0 13 13 3100
+
+Based on turbostat output, the performance is limited by frequency cap of 3100
+MHz. To check if the hackbench performance can be improved for CPU 12 and CPU
+13, first check the capability of the Intel SST-TF feature for this performance
+level.
+
+Get Intel SST-TF Capability
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+To get the capability, the "turbo-freq info" command can be used::
+
+ # intel-speed-select turbo-freq info -l 0
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ package-0
+ die-0
+ cpu-0
+ speed-select-turbo-freq
+ bucket-0
+ high-priority-cores-count:2
+ high-priority-max-frequency(MHz):3200
+ high-priority-max-avx2-frequency(MHz):3200
+ high-priority-max-avx512-frequency(MHz):3100
+ bucket-1
+ high-priority-cores-count:4
+ high-priority-max-frequency(MHz):3100
+ high-priority-max-avx2-frequency(MHz):3000
+ high-priority-max-avx512-frequency(MHz):2900
+ bucket-2
+ high-priority-cores-count:6
+ high-priority-max-frequency(MHz):3100
+ high-priority-max-avx2-frequency(MHz):3000
+ high-priority-max-avx512-frequency(MHz):2900
+ speed-select-turbo-freq-clip-frequencies
+ low-priority-max-frequency(MHz):2600
+ low-priority-max-avx2-frequency(MHz):2400
+ low-priority-max-avx512-frequency(MHz):2100
+
+Based on the output above, there is an Intel SST-TF bucket for which there are
+two high priority cores. If only two high priority cores are set, then max.
+turbo frequency on those cores can be increased to 3200 MHz. This is 100 MHz
+more than the base turbo capability for all cores.
+
+In turn, for the hackbench workload, two CPUs can be set as high priority and
+rest as low priority. One side effect is that once enabled, the low priority
+cores will be clipped to a lower frequency of 2600 MHz.
+
+Enable Intel SST-TF
+~~~~~~~~~~~~~~~~~~~
+
+To enable Intel SST-TF, execute::
+
+ # intel-speed-select -c 12,13 turbo-freq enable -a
+ Intel(R) Speed Select Technology
+ Executing on CPU model: X
+ package-0
+ die-0
+ cpu-12
+ turbo-freq
+ enable:success
+ package-0
+ die-0
+ cpu-13
+ turbo-freq
+ enable:success
+ package--1
+ die-0
+ cpu-63
+ turbo-freq --auto
+ enable:success
+
+In this case, the option "-a" is optional. If set, it enables Intel SST-TF
+feature and also sets the CPUs to high and and low priority using Intel Speed
+Select Technology â Core Power (Intel SST-CP) features. The CPU numbers passed
+with "-c" arguments are marked as high priority, including its siblings.
+
+If -a option is not used, then the following steps are required before enabling
+Intel SST-TF:
+
+- Discover Intel SST-TF and note buckets of high priority cores and maximum frequency
+
+- Enable CLOS using core-power feature set - Configure CLOS parameters
+
+- Subscribe desired CPUs to CLOS groups making sure that high priority cores are set to the maximum frequency
+
+If the same hackbench workload is executed, schedule hackbench threads on high
+priority CPUs::
+
+ #taskset -c 12,13 perf bench -r 100 sched pipe
+ # Running 'sched/pipe' benchmark:
+ # Executed 1000000 pipe operations between two processes
+ Total time: 5.510 [sec]
+ 5.510165 usecs/op
+ 180826 ops/sec
+
+This improved performance by around 3.3% improvement on a busy system. Here the
+turbostat output will show that the CPU 12 and CPU 13 are getting 100 MHz boost.
+The turbostat output::
+
+ #turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1
+ Package Core CPU Bzy_MHz
+ ...
+ 0 12 12 3200
+ 0 13 13 3200
diff --git a/Documentation/admin-guide/pm/working-state.rst b/Documentation/admin-guide/pm/working-state.rst
index fc298eb1234b..06d1403b1597 100644
--- a/Documentation/admin-guide/pm/working-state.rst
+++ b/Documentation/admin-guide/pm/working-state.rst
@@ -11,3 +11,4 @@ Working-State Power Management
cpufreq
intel_pstate
intel_epb
+ intel-speed-select
--
2.17.2