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Fix thirty five typos in dm-integrity.rst, dm-raid.rst, dm-zoned.rst, verity.rst, writecache.rst, tsx_async_abort.rst, md.rst, bttv.rst, dvb_references.rst, frontend-cardlist.rst, gspca-cardlist.rst, ipu3.rst, remote-controller.rst, mm/index.rst, numaperf.rst, userfaultfd.rst, module-signing.rst, imx-ddr.rst, intel-speed-select.rst, intel_pstate.rst, ramoops.rst, abi.rst, kernel.rst, vm.rst Signed-off-by: Andrew Klychkov <andrew.a.klychkov@gmail.com> Link: https://lore.kernel.org/r/20201204072848.GA49895@spblnx124.lan Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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============================================================
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Intel(R) Speed Select Technology User Guide
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============================================================
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The Intel(R) Speed Select Technology (Intel(R) SST) provides a powerful new
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collection of features that give more granular control over CPU performance.
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With Intel(R) SST, one server can be configured for power and performance for a
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variety of diverse workload requirements.
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Refer to the links below for an overview of the technology:
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- https://www.intel.com/content/www/us/en/architecture-and-technology/speed-select-technology-article.html
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- https://builders.intel.com/docs/networkbuilders/intel-speed-select-technology-base-frequency-enhancing-performance.pdf
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These capabilities are further enhanced in some of the newer generations of
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server platforms where these features can be enumerated and controlled
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dynamically without pre-configuring via BIOS setup options. This dynamic
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configuration is done via mailbox commands to the hardware. One way to enumerate
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and configure these features is by using the Intel Speed Select utility.
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This document explains how to use the Intel Speed Select tool to enumerate and
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control Intel(R) SST features. This document gives example commands and explains
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how these commands change the power and performance profile of the system under
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test. Using this tool as an example, customers can replicate the messaging
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implemented in the tool in their production software.
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intel-speed-select configuration tool
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======================================
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Most Linux distribution packages may include the "intel-speed-select" tool. If not,
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it can be built by downloading the Linux kernel tree from kernel.org. Once
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downloaded, the tool can be built without building the full kernel.
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From the kernel tree, run the following commands::
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# cd tools/power/x86/intel-speed-select/
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# make
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# make install
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Getting Help
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------------
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To get help with the tool, execute the command below::
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# intel-speed-select --help
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The top-level help describes arguments and features. Notice that there is a
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multi-level help structure in the tool. For example, to get help for the feature "perf-profile"::
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# intel-speed-select perf-profile --help
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To get help on a command, another level of help is provided. For example for the command info "info"::
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# intel-speed-select perf-profile info --help
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Summary of platform capability
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------------------------------
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To check the current platform and driver capabilities, execute::
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#intel-speed-select --info
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For example on a test system::
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# intel-speed-select --info
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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Platform: API version : 1
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Platform: Driver version : 1
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Platform: mbox supported : 1
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Platform: mmio supported : 1
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Intel(R) SST-PP (feature perf-profile) is supported
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TDP level change control is unlocked, max level: 4
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Intel(R) SST-TF (feature turbo-freq) is supported
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Intel(R) SST-BF (feature base-freq) is not supported
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Intel(R) SST-CP (feature core-power) is supported
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Intel(R) Speed Select Technology - Performance Profile (Intel(R) SST-PP)
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------------------------------------------------------------------------
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This feature allows configuration of a server dynamically based on workload
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performance requirements. This helps users during deployment as they do not have
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to choose a specific server configuration statically. This Intel(R) Speed Select
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Technology - Performance Profile (Intel(R) SST-PP) feature introduces a mechanism
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that allows multiple optimized performance profiles per system. Each profile
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defines a set of CPUs that need to be online and rest offline to sustain a
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guaranteed base frequency. Once the user issues a command to use a specific
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performance profile and meet CPU online/offline requirement, the user can expect
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a change in the base frequency dynamically. This feature is called
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"perf-profile" when using the Intel Speed Select tool.
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Number or performance levels
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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There can be multiple performance profiles on a system. To get the number of
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profiles, execute the command below::
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# intel-speed-select perf-profile get-config-levels
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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package-0
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die-0
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cpu-0
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get-config-levels:4
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package-1
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die-0
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cpu-14
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get-config-levels:4
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On this system under test, there are 4 performance profiles in addition to the
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base performance profile (which is performance level 0).
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Lock/Unlock status
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~~~~~~~~~~~~~~~~~~
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Even if there are multiple performance profiles, it is possible that they
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are locked. If they are locked, users cannot issue a command to change the
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performance state. It is possible that there is a BIOS setup to unlock or check
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with your system vendor.
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To check if the system is locked, execute the following command::
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# intel-speed-select perf-profile get-lock-status
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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package-0
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die-0
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cpu-0
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get-lock-status:0
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package-1
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die-0
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cpu-14
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get-lock-status:0
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In this case, lock status is 0, which means that the system is unlocked.
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Properties of a performance level
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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To get properties of a specific performance level (For example for the level 0, below), execute the command below::
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# intel-speed-select perf-profile info -l 0
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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package-0
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die-0
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cpu-0
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perf-profile-level-0
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cpu-count:28
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enable-cpu-mask:000003ff,f0003fff
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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
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thermal-design-power-ratio:26
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base-frequency(MHz):2600
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speed-select-turbo-freq:disabled
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speed-select-base-freq:disabled
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...
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...
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Here -l option is used to specify a performance level.
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If the option -l is omitted, then this command will print information about all
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the performance levels. The above command is printing properties of the
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performance level 0.
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For this performance profile, the list of CPUs displayed by the
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"enable-cpu-mask/enable-cpu-list" at the max can be "online." When that
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condition is met, then base frequency of 2600 MHz can be maintained. To
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understand more, execute "intel-speed-select perf-profile info" for performance
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level 4::
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# intel-speed-select perf-profile info -l 4
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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package-0
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die-0
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cpu-0
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perf-profile-level-4
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cpu-count:28
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enable-cpu-mask:000000fa,f0000faf
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enable-cpu-list:0,1,2,3,5,7,8,9,10,11,28,29,30,31,33,35,36,37,38,39
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thermal-design-power-ratio:28
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base-frequency(MHz):2800
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speed-select-turbo-freq:disabled
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speed-select-base-freq:unsupported
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...
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...
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There are fewer CPUs in the "enable-cpu-mask/enable-cpu-list". Consequently, if
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the user only keeps these CPUs online and the rest "offline," then the base
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frequency is increased to 2.8 GHz compared to 2.6 GHz at performance level 0.
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Get current performance level
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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To get the current performance level, execute::
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# intel-speed-select perf-profile get-config-current-level
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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package-0
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die-0
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cpu-0
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get-config-current_level:0
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First verify that the base_frequency displayed by the cpufreq sysfs is correct::
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# cat /sys/devices/system/cpu/cpu0/cpufreq/base_frequency
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2600000
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This matches the base-frequency (MHz) field value displayed from the
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"perf-profile info" command for performance level 0(cpufreq frequency is in
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KHz).
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To check if the average frequency is equal to the base frequency for a 100% busy
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workload, disable turbo::
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# echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo
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Then runs a busy workload on all CPUs, for example::
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#stress -c 64
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To verify the base frequency, run turbostat::
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#turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1
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Package Core CPU Bzy_MHz
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- - 2600
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0 0 0 2600
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0 1 1 2600
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0 2 2 2600
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0 3 3 2600
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0 4 4 2600
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. . . .
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Changing performance level
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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To the change the performance level to 4, execute::
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# intel-speed-select -d perf-profile set-config-level -l 4 -o
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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package-0
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die-0
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cpu-0
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perf-profile
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set_tdp_level:success
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In the command above, "-o" is optional. If it is specified, then it will also
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offline CPUs which are not present in the enable_cpu_mask for this performance
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level.
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Now if the base_frequency is checked::
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#cat /sys/devices/system/cpu/cpu0/cpufreq/base_frequency
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2800000
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Which shows that the base frequency now increased from 2600 MHz at performance
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level 0 to 2800 MHz at performance level 4. As a result, any workload, which can
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use fewer CPUs, can see a boost of 200 MHz compared to performance level 0.
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Check presence of other Intel(R) SST features
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---------------------------------------------
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Each of the performance profiles also specifies weather there is support of
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other two Intel(R) SST features (Intel(R) Speed Select Technology - Base Frequency
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(Intel(R) SST-BF) and Intel(R) Speed Select Technology - Turbo Frequency (Intel
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SST-TF)).
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For example, from the output of "perf-profile info" above, for level 0 and level
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4:
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For level 0::
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speed-select-turbo-freq:disabled
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speed-select-base-freq:disabled
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For level 4::
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speed-select-turbo-freq:disabled
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speed-select-base-freq:unsupported
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Given these results, the "speed-select-base-freq" (Intel(R) SST-BF) in level 4
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changed from "disabled" to "unsupported" compared to performance level 0.
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This means that at performance level 4, the "speed-select-base-freq" feature is
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not supported. However, at performance level 0, this feature is "supported", but
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currently "disabled", meaning the user has not activated this feature. Whereas
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"speed-select-turbo-freq" (Intel(R) SST-TF) is supported at both performance
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levels, but currently not activated by the user.
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The Intel(R) SST-BF and the Intel(R) SST-TF features are built on a foundation
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technology called Intel(R) Speed Select Technology - Core Power (Intel(R) SST-CP).
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The platform firmware enables this feature when Intel(R) SST-BF or Intel(R) SST-TF
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is supported on a platform.
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Intel(R) Speed Select Technology Core Power (Intel(R) SST-CP)
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---------------------------------------------------------------
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Intel(R) Speed Select Technology Core Power (Intel(R) SST-CP) is an interface that
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allows users to define per core priority. This defines a mechanism to distribute
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power among cores when there is a power constrained scenario. This defines a
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class of service (CLOS) configuration.
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The user can configure up to 4 class of service configurations. Each CLOS group
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configuration allows definitions of parameters, which affects how the frequency
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can be limited and power is distributed. Each CPU core can be tied to a class of
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service and hence an associated priority. The granularity is at core level not
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at per CPU level.
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Enable CLOS based prioritization
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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To use CLOS based prioritization feature, firmware must be informed to enable
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and use a priority type. There is a default per platform priority type, which
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can be changed with optional command line parameter.
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To enable and check the options, execute::
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# intel-speed-select core-power enable --help
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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Enable core-power for a package/die
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Clos Enable: Specify priority type with [--priority|-p]
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0: Proportional, 1: Ordered
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There are two types of priority types:
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- Ordered
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Priority for ordered throttling is defined based on the index of the assigned
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CLOS group. Where CLOS0 gets highest priority (throttled last).
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Priority order is:
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CLOS0 > CLOS1 > CLOS2 > CLOS3.
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- Proportional
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When proportional priority is used, there is an additional parameter called
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frequency_weight, which can be specified per CLOS group. The goal of
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proportional priority is to provide each core with the requested min., then
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distribute all remaining (excess/deficit) budgets in proportion to a defined
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weight. This proportional priority can be configured using "core-power config"
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command.
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To enable with the platform default priority type, execute::
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# intel-speed-select core-power enable
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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package-0
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die-0
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cpu-0
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core-power
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enable:success
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package-1
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die-0
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cpu-6
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core-power
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enable:success
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The scope of this enable is per package or die scoped when a package contains
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multiple dies. To check if CLOS is enabled and get priority type, "core-power
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info" command can be used. For example to check the status of core-power feature
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on CPU 0, execute::
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# intel-speed-select -c 0 core-power info
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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package-0
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die-0
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cpu-0
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core-power
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support-status:supported
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enable-status:enabled
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clos-enable-status:enabled
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priority-type:proportional
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package-1
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die-0
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cpu-24
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core-power
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support-status:supported
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enable-status:enabled
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clos-enable-status:enabled
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priority-type:proportional
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Configuring CLOS groups
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~~~~~~~~~~~~~~~~~~~~~~~
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Each CLOS group has its own attributes including min, max, freq_weight and
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desired. These parameters can be configured with "core-power config" command.
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Defaults will be used if user skips setting a parameter except clos id, which is
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mandatory. To check core-power config options, execute::
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# intel-speed-select core-power config --help
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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Set core-power configuration for one of the four clos ids
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Specify targeted clos id with [--clos|-c]
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Specify clos Proportional Priority [--weight|-w]
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Specify clos min in MHz with [--min|-n]
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Specify clos max in MHz with [--max|-m]
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For example::
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# intel-speed-select core-power config -c 0
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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clos epp is not specified, default: 0
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clos frequency weight is not specified, default: 0
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clos min is not specified, default: 0 MHz
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clos max is not specified, default: 25500 MHz
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clos desired is not specified, default: 0
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package-0
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die-0
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cpu-0
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core-power
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config:success
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package-1
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die-0
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cpu-6
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core-power
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config:success
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The user has the option to change defaults. For example, the user can change the
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"min" and set the base frequency to always get guaranteed base frequency.
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Get the current CLOS configuration
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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To check the current configuration, "core-power get-config" can be used. For
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example, to get the configuration of CLOS 0::
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# intel-speed-select core-power get-config -c 0
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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package-0
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die-0
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cpu-0
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core-power
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clos:0
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epp:0
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clos-proportional-priority:0
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clos-min:0 MHz
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clos-max:Max Turbo frequency
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clos-desired:0 MHz
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package-1
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die-0
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cpu-24
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core-power
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clos:0
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epp:0
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clos-proportional-priority:0
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clos-min:0 MHz
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clos-max:Max Turbo frequency
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clos-desired:0 MHz
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Associating a CPU with a CLOS group
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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To associate a CPU to a CLOS group "core-power assoc" command can be used::
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# intel-speed-select core-power assoc --help
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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Associate a clos id to a CPU
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Specify targeted clos id with [--clos|-c]
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For example to associate CPU 10 to CLOS group 3, execute::
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# intel-speed-select -c 10 core-power assoc -c 3
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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package-0
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die-0
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cpu-10
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core-power
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assoc:success
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Once a CPU is associated, its sibling CPUs are also associated to a CLOS group.
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Once associated, avoid changing Linux "cpufreq" subsystem scaling frequency
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limits.
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To check the existing association for a CPU, "core-power get-assoc" command can
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be used. For example, to get association of CPU 10, execute::
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# intel-speed-select -c 10 core-power get-assoc
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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package-1
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die-0
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cpu-10
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get-assoc
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clos:3
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This shows that CPU 10 is part of a CLOS group 3.
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Disable CLOS based prioritization
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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To disable, execute::
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# intel-speed-select core-power disable
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Some features like Intel(R) SST-TF can only be enabled when CLOS based prioritization
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is enabled. For this reason, disabling while Intel(R) SST-TF is enabled can cause
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Intel(R) SST-TF to fail. This will cause the "disable" command to display an error
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if Intel(R) SST-TF is already enabled. In turn, to disable, the Intel(R) SST-TF
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feature must be disabled first.
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|
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Intel(R) Speed Select Technology - Base Frequency (Intel(R) SST-BF)
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-------------------------------------------------------------------
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The Intel(R) Speed Select Technology - Base Frequency (Intel(R) SST-BF) feature lets
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the user control base frequency. If some critical workload threads demand
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constant high guaranteed performance, then this feature can be used to execute
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the thread at higher base frequency on specific sets of CPUs (high priority
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CPUs) at the cost of lower base frequency (low priority CPUs) on other CPUs.
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This feature does not require offline of the low priority CPUs.
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The support of Intel(R) SST-BF depends on the Intel(R) Speed Select Technology -
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Performance Profile (Intel(R) SST-PP) performance level configuration. It is
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possible that only certain performance levels support Intel(R) SST-BF. It is also
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possible that only base performance level (level = 0) has support of Intel
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SST-BF. Consequently, first select the desired performance level to enable this
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feature.
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In the system under test here, Intel(R) SST-BF is supported at the base
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performance level 0, but currently disabled. For example for the level 0::
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# intel-speed-select -c 0 perf-profile info -l 0
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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package-0
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die-0
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cpu-0
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perf-profile-level-0
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...
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speed-select-base-freq:disabled
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...
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Before enabling Intel(R) SST-BF and measuring its impact on a workload
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performance, execute some workload and measure performance and get a baseline
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performance to compare against.
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Here the user wants more guaranteed performance. For this reason, it is likely
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that turbo is disabled. To disable turbo, execute::
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#echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo
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Based on the output of the "intel-speed-select perf-profile info -l 0" base
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frequency of guaranteed frequency 2600 MHz.
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Measure baseline performance for comparison
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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To compare, pick a multi-threaded workload where each thread can be scheduled on
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separate CPUs. "Hackbench pipe" test is a good example on how to improve
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performance using Intel(R) SST-BF.
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Below, the workload is measuring average scheduler wakeup latency, so a lower
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number means better performance::
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# taskset -c 3,4 perf bench -r 100 sched pipe
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# Running 'sched/pipe' benchmark:
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# Executed 1000000 pipe operations between two processes
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Total time: 6.102 [sec]
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6.102445 usecs/op
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163868 ops/sec
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While running the above test, if we take turbostat output, it will show us that
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2 of the CPUs are busy and reaching max. frequency (which would be the base
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frequency as the turbo is disabled). The turbostat output::
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#turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1
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Package Core CPU Bzy_MHz
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0 0 0 1000
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0 1 1 1005
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0 2 2 1000
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0 3 3 2600
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0 4 4 2600
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0 5 5 1000
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0 6 6 1000
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0 7 7 1005
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0 8 8 1005
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0 9 9 1000
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0 10 10 1000
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0 11 11 995
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0 12 12 1000
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0 13 13 1000
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From the above turbostat output, both CPU 3 and 4 are very busy and reaching
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full guaranteed frequency of 2600 MHz.
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Intel(R) SST-BF Capabilities
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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To get capabilities of Intel(R) SST-BF for the current performance level 0,
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execute::
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# intel-speed-select base-freq info -l 0
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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package-0
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die-0
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cpu-0
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speed-select-base-freq
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high-priority-base-frequency(MHz):3000
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high-priority-cpu-mask:00000216,00002160
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high-priority-cpu-list:5,6,8,13,33,34,36,41
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low-priority-base-frequency(MHz):2400
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tjunction-temperature(C):125
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thermal-design-power(W):205
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The above capabilities show that there are some CPUs on this system that can
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offer base frequency of 3000 MHz compared to the standard base frequency at this
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performance levels. Nevertheless, these CPUs are fixed, and they are presented
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via high-priority-cpu-list/high-priority-cpu-mask. But if this Intel(R) SST-BF
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feature is selected, the low priorities CPUs (which are not in
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high-priority-cpu-list) can only offer up to 2400 MHz. As a result, if this
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clipping of low priority CPUs is acceptable, then the user can enable Intel
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SST-BF feature particularly for the above "sched pipe" workload since only two
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CPUs are used, they can be scheduled on high priority CPUs and can get boost of
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400 MHz.
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Enable Intel(R) SST-BF
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~~~~~~~~~~~~~~~~~~~~~~
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To enable Intel(R) SST-BF feature, execute::
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# intel-speed-select base-freq enable -a
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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package-0
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die-0
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cpu-0
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base-freq
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enable:success
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package-1
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die-0
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cpu-14
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base-freq
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enable:success
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In this case, -a option is optional. This not only enables Intel(R) SST-BF, but it
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also adjusts the priority of cores using Intel(R) Speed Select Technology Core
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Power (Intel(R) SST-CP) features. This option sets the minimum performance of each
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Intel(R) Speed Select Technology - Performance Profile (Intel(R) SST-PP) class to
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maximum performance so that the hardware will give maximum performance possible
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for each CPU.
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If -a option is not used, then the following steps are required before enabling
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Intel(R) SST-BF:
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- Discover Intel(R) SST-BF and note low and high priority base frequency
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- Note the high priority CPU list
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- Enable CLOS using core-power feature set
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- Configure CLOS parameters. Use CLOS.min to set to minimum performance
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- Subscribe desired CPUs to CLOS groups
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With this configuration, if the same workload is executed by pinning the
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workload to high priority CPUs (CPU 5 and 6 in this case)::
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#taskset -c 5,6 perf bench -r 100 sched pipe
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# Running 'sched/pipe' benchmark:
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# Executed 1000000 pipe operations between two processes
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Total time: 5.627 [sec]
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5.627922 usecs/op
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177685 ops/sec
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This way, by enabling Intel(R) SST-BF, the performance of this benchmark is
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improved (latency reduced) by 7.79%. From the turbostat output, it can be
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observed that the high priority CPUs reached 3000 MHz compared to 2600 MHz.
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The turbostat output::
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#turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1
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Package Core CPU Bzy_MHz
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0 0 0 2151
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0 1 1 2166
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0 2 2 2175
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0 3 3 2175
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0 4 4 2175
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0 5 5 3000
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0 6 6 3000
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0 7 7 2180
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0 8 8 2662
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0 9 9 2176
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0 10 10 2175
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0 11 11 2176
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0 12 12 2176
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0 13 13 2661
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Disable Intel(R) SST-BF
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~~~~~~~~~~~~~~~~~~~~~~~
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To disable the Intel(R) SST-BF feature, execute::
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# intel-speed-select base-freq disable -a
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Intel(R) Speed Select Technology - Turbo Frequency (Intel(R) SST-TF)
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--------------------------------------------------------------------
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This feature enables the ability to set different "All core turbo ratio limits"
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to cores based on the priority. By using this feature, some cores can be
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configured to get higher turbo frequency by designating them as high priority at
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the cost of lower or no turbo frequency on the low priority cores.
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For this reason, this feature is only useful when system is busy utilizing all
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CPUs, but the user wants some configurable option to get high performance on
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some CPUs.
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The support of Intel(R) Speed Select Technology - Turbo Frequency (Intel(R) SST-TF)
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depends on the Intel(R) Speed Select Technology - Performance Profile (Intel
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SST-PP) performance level configuration. It is possible that only a certain
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performance level supports Intel(R) SST-TF. It is also possible that only the base
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performance level (level = 0) has the support of Intel(R) SST-TF. Hence, first
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select the desired performance level to enable this feature.
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In the system under test here, Intel(R) SST-TF is supported at the base
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performance level 0, but currently disabled::
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# intel-speed-select -c 0 perf-profile info -l 0
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Intel(R) Speed Select Technology
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package-0
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die-0
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cpu-0
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perf-profile-level-0
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...
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...
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speed-select-turbo-freq:disabled
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...
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...
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To check if performance can be improved using Intel(R) SST-TF feature, get the turbo
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frequency properties with Intel(R) SST-TF enabled and compare to the base turbo
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capability of this system.
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Get Base turbo capability
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~~~~~~~~~~~~~~~~~~~~~~~~~
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To get the base turbo capability of performance level 0, execute::
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# intel-speed-select perf-profile info -l 0
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Intel(R) Speed Select Technology
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Executing on CPU model: X
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package-0
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die-0
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cpu-0
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perf-profile-level-0
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...
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...
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turbo-ratio-limits-sse
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bucket-0
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core-count:2
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max-turbo-frequency(MHz):3200
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bucket-1
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core-count:4
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max-turbo-frequency(MHz):3100
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bucket-2
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core-count:6
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max-turbo-frequency(MHz):3100
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bucket-3
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core-count:8
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max-turbo-frequency(MHz):3100
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bucket-4
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core-count:10
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max-turbo-frequency(MHz):3100
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bucket-5
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core-count:12
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max-turbo-frequency(MHz):3100
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bucket-6
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core-count:14
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max-turbo-frequency(MHz):3100
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bucket-7
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core-count:16
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max-turbo-frequency(MHz):3100
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Based on the data above, when all the CPUS are busy, the max. frequency of 3100
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MHz can be achieved. If there is some busy workload on cpu 0 - 11 (e.g. stress)
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and on CPU 12 and 13, execute "hackbench pipe" workload::
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# taskset -c 12,13 perf bench -r 100 sched pipe
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# Running 'sched/pipe' benchmark:
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# Executed 1000000 pipe operations between two processes
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Total time: 5.705 [sec]
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5.705488 usecs/op
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175269 ops/sec
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The turbostat output::
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#turbostat -c 0-13 --show Package,Core,CPU,Bzy_MHz -i 1
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Package Core CPU Bzy_MHz
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0 0 0 3000
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0 1 1 3000
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0 2 2 3000
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0 3 3 3000
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0 4 4 3000
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0 5 5 3100
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0 6 6 3100
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0 7 7 3000
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0 8 8 3100
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0 9 9 3000
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0 10 10 3000
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0 11 11 3000
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0 12 12 3100
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0 13 13 3100
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Based on turbostat output, the performance is limited by frequency cap of 3100
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MHz. To check if the hackbench performance can be improved for CPU 12 and CPU
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13, first check the capability of the Intel(R) SST-TF feature for this performance
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level.
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Get Intel(R) SST-TF Capability
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
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|
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To get the capability, the "turbo-freq info" command can be used::
|
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|
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# intel-speed-select turbo-freq info -l 0
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Intel(R) Speed Select Technology
|
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Executing on CPU model: X
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package-0
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die-0
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cpu-0
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speed-select-turbo-freq
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bucket-0
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high-priority-cores-count:2
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high-priority-max-frequency(MHz):3200
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high-priority-max-avx2-frequency(MHz):3200
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high-priority-max-avx512-frequency(MHz):3100
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bucket-1
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high-priority-cores-count:4
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high-priority-max-frequency(MHz):3100
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high-priority-max-avx2-frequency(MHz):3000
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high-priority-max-avx512-frequency(MHz):2900
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bucket-2
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high-priority-cores-count:6
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high-priority-max-frequency(MHz):3100
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high-priority-max-avx2-frequency(MHz):3000
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high-priority-max-avx512-frequency(MHz):2900
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speed-select-turbo-freq-clip-frequencies
|
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low-priority-max-frequency(MHz):2600
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low-priority-max-avx2-frequency(MHz):2400
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low-priority-max-avx512-frequency(MHz):2100
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Based on the output above, there is an Intel(R) SST-TF bucket for which there are
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two high priority cores. If only two high priority cores are set, then max.
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turbo frequency on those cores can be increased to 3200 MHz. This is 100 MHz
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more than the base turbo capability for all cores.
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|
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In turn, for the hackbench workload, two CPUs can be set as high priority and
|
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rest as low priority. One side effect is that once enabled, the low priority
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cores will be clipped to a lower frequency of 2600 MHz.
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|
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Enable Intel(R) SST-TF
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~~~~~~~~~~~~~~~~~~~~~~
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To enable Intel(R) SST-TF, execute::
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|
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# intel-speed-select -c 12,13 turbo-freq enable -a
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Intel(R) Speed Select Technology
|
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Executing on CPU model: X
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package-0
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die-0
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cpu-12
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turbo-freq
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enable:success
|
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package-0
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die-0
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cpu-13
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turbo-freq
|
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enable:success
|
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package--1
|
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die-0
|
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cpu-63
|
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turbo-freq --auto
|
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enable:success
|
|
|
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In this case, the option "-a" is optional. If set, it enables Intel(R) SST-TF
|
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feature and also sets the CPUs to high and low priority using Intel Speed
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Select Technology Core Power (Intel(R) SST-CP) features. The CPU numbers passed
|
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with "-c" arguments are marked as high priority, including its siblings.
|
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|
|
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
|
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|
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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
|
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Total time: 5.510 [sec]
|
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5.510165 usecs/op
|
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180826 ops/sec
|
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|
|
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
|
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...
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0 12 12 3200
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0 13 13 3200
|