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Message-ID: <CAJZ5v0irj_vZVJc7TxBocfO7g8wPpYWu145qXGsZ5xoDk3yz8w@mail.gmail.com>
Date: Tue, 19 May 2020 20:02:27 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc: Rafael Wysocki <rafael.j.wysocki@...el.com>,
Jonathan Corbet <corbet@....net>,
Andy Shevchenko <andy.shevchenko@...il.com>,
Randy Dunlap <rdunlap@...radead.org>,
"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Linux PM <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v3] admin guide/pm: Admin guide for intel-speed-select
On Tue, May 12, 2020 at 1:57 AM Srinivas Pandruvada
<srinivas.pandruvada@...ux.intel.com> wrote:
>
> Added documentation to configure servers to use Intel(R) Speed
> Select Technology using intel-speed-select tool.
>
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> Acked-by: Andriy Shevchenko <andy.shevchenko@...il.com>
Applied as 5.8 material, thanks!
> ---
> v3:
> - Match the command results with the latest tool and added to this documentation.
> Tool made some "numbers" to more verbose display, so change documentation
> also.
>
> v2:
> Only formatting changes. So used ACK from Andriy.
> Addressed comments by Jonathan for the following items:
> - Removed non ASCII character
> - Addressed section/sub-section markers
> - Folded all commands and outputs in literal blocks
>
>
> .../admin-guide/pm/intel-speed-select.rst | 917 ++++++++++++++++++
> .../admin-guide/pm/working-state.rst | 1 +
> 2 files changed, 918 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
> new file mode 100644
> index 000000000000..b2ca601c21c6
> --- /dev/null
> +++ b/Documentation/admin-guide/pm/intel-speed-select.rst
> @@ -0,0 +1,917 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +============================================================
> +Intel(R) Speed Select Technology User Guide
> +============================================================
> +
> +The Intel(R) Speed Select Technology (Intel(R) SST) provides a powerful new
> +collection of features that give more granular control over CPU performance.
> +With Intel(R) 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(R) 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
> +
> +Summary of platform capability
> +------------------------------
> +To check the current platform and driver capaibilities, execute::
> +
> +#intel-speed-select --info
> +
> +For example on a test system::
> +
> + # intel-speed-select --info
> + Intel(R) Speed Select Technology
> + Executing on CPU model: X
> + Platform: API version : 1
> + Platform: Driver version : 1
> + Platform: mbox supported : 1
> + Platform: mmio supported : 1
> + Intel(R) SST-PP (feature perf-profile) is supported
> + TDP level change control is unlocked, max level: 4
> + Intel(R) SST-TF (feature turbo-freq) is supported
> + Intel(R) SST-BF (feature base-freq) is not supported
> + Intel(R) SST-CP (feature core-power) is supported
> +
> +Intel(R) Speed Select Technology - Performance Profile (Intel(R) 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(R) Speed Select
> +Technology - Performance Profile (Intel(R) 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 "enable-cpu-mask/enable-cpu-list". 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(R) SST features
> +---------------------------------------------
> +
> +Each of the performance profiles also specifies weather there is support of
> +other two Intel(R) SST features (Intel(R) Speed Select Technology - Base Frequency
> +(Intel(R) SST-BF) and Intel(R) 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 "speed-select-base-freq" (Intel(R) 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(R) SST-TF) is supported at both performance
> +levels, but currently not activated by the user.
> +
> +The Intel(R) SST-BF and the Intel(R) SST-TF features are built on a foundation
> +technology called Intel(R) Speed Select Technology - Core Power (Intel(R) SST-CP).
> +The platform firmware enables this feature when Intel(R) SST-BF or Intel(R) SST-TF
> +is supported on a platform.
> +
> +Intel(R) Speed Select Technology Core Power (Intel(R) SST-CP)
> +---------------------------------------------------------------
> +
> +Intel(R) Speed Select Technology Core Power (Intel(R) 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
> + support-status:supported
> + enable-status:enabled
> + clos-enable-status:enabled
> + priority-type:proportional
> + package-1
> + die-0
> + cpu-24
> + core-power
> + support-status:supported
> + enable-status:enabled
> + clos-enable-status:enabled
> + priority-type:proportional
> +
> +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]
> +
> +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:Max Turbo frequency
> + clos-desired:0 MHz
> + package-1
> + die-0
> + cpu-24
> + core-power
> + clos:0
> + epp:0
> + clos-proportional-priority:0
> + clos-min:0 MHz
> + clos-max:Max Turbo frequency
> + clos-desired:0 MHz
> +
> +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 "cpufreq" 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(R) SST-TF can only be enabled when CLOS based prioritization
> +is enabled. For this reason, disabling while Intel(R) SST-TF is enabled can cause
> +Intel(R) SST-TF to fail. This will cause the "disable" command to display an error
> +if Intel(R) SST-TF is already enabled. In turn, to disable, the Intel(R) SST-TF
> +feature must be disabled first.
> +
> +Intel(R) Speed Select Technology - Base Frequency (Intel(R) SST-BF)
> +-------------------------------------------------------------------
> +
> +The Intel(R) Speed Select Technology - Base Frequency (Intel(R) 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(R) SST-BF depends on the Intel(R) Speed Select Technology -
> +Performance Profile (Intel(R) SST-PP) performance level configuration. It is
> +possible that only certain performance levels support Intel(R) 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(R) 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(R) 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(R) 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(R) SST-BF Capabilities
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +To get capabilities of Intel(R) 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(R) 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(R) SST-BF
> +~~~~~~~~~~~~~~~~~~~~~~
> +
> +To enable Intel(R) 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(R) SST-BF, but it
> +also adjusts the priority of cores using Intel(R) Speed Select Technology Core
> +Power (Intel(R) SST-CP) features. This option sets the minimum performance of each
> +Intel(R) Speed Select Technology - Performance Profile (Intel(R) 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(R) SST-BF:
> +
> +- Discover Intel(R) 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(R) 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(R) SST-BF
> +~~~~~~~~~~~~~~~~~~~~~~~
> +
> +To disable the Intel(R) SST-BF feature, execute::
> +
> +# intel-speed-select base-freq disable -a
> +
> +
> +Intel(R) Speed Select Technology - Turbo Frequency (Intel(R) 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(R) Speed Select Technology - Turbo Frequency (Intel(R) SST-TF)
> +depends on the Intel(R) Speed Select Technology - Performance Profile (Intel
> +SST-PP) performance level configuration. It is possible that only a certain
> +performance level supports Intel(R) SST-TF. It is also possible that only the base
> +performance level (level = 0) has the support of Intel(R) SST-TF. Hence, first
> +select the desired performance level to enable this feature.
> +
> +In the system under test here, Intel(R) 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(R) SST-TF feature, get the turbo
> +frequency properties with Intel(R) 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(R) SST-TF feature for this performance
> +level.
> +
> +Get Intel(R) 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(R) 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(R) SST-TF
> +~~~~~~~~~~~~~~~~~~~~~~
> +
> +To enable Intel(R) 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(R) SST-TF
> +feature and also sets the CPUs to high and and low priority using Intel Speed
> +Select Technology Core Power (Intel(R) 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(R) SST-TF:
> +
> +- Discover Intel(R) 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 0a38cdf39df1..f40994c422dc 100644
> --- a/Documentation/admin-guide/pm/working-state.rst
> +++ b/Documentation/admin-guide/pm/working-state.rst
> @@ -13,3 +13,4 @@ Working-State Power Management
> intel_pstate
> cpufreq_drivers
> intel_epb
> + intel-speed-select
> --
> 2.25.4
>
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