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Documentation: ACPI: move cppc_sysfs.txt to admin-guide/acpi and convert to reST

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This converts the plain text documentation to reStructuredText format
and adds it to Sphinx TOC tree.

No essential content change.

Signed-off-by: Changbin Du <changbin.du@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Changbin Du 2019-04-25 01:53:03 +08:00 • committed by Rafael J. Wysocki
parent 440ebec745
commit 3e57460f00
2 changed files with 40 additions and 32 deletions
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69
Documentation/acpi/cppc_sysfs.txt → Documentation/admin-guide/acpi/cppc_sysfs.rst
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@ -1,5 +1,11 @@
.. SPDX-License-Identifier: GPL-2.0
Collaborative Processor Performance Control (CPPC) ==================================================
Collaborative Processor Performance Control (CPPC)
==================================================
CPPC
====
CPPC defined in the ACPI spec describes a mechanism for the OS to manage the CPPC defined in the ACPI spec describes a mechanism for the OS to manage the
performance of a logical processor on a contigious and abstract performance performance of a logical processor on a contigious and abstract performance
@ -10,31 +16,28 @@ For more details on CPPC please refer to the ACPI specification at:
http://uefi.org/specifications http://uefi.org/specifications
Some of the CPPC registers are exposed via sysfs under: Some of the CPPC registers are exposed via sysfs under::
/sys/devices/system/cpu/cpuX/acpi_cppc/ /sys/devices/system/cpu/cpuX/acpi_cppc/
for each cpu X for each cpu X::
-------------------------------------------------------------------------------- $ ls -lR /sys/devices/system/cpu/cpu0/acpi_cppc/
/sys/devices/system/cpu/cpu0/acpi_cppc/:
$ ls -lR /sys/devices/system/cpu/cpu0/acpi_cppc/ total 0
/sys/devices/system/cpu/cpu0/acpi_cppc/: -r--r--r-- 1 root root 65536 Mar 5 19:38 feedback_ctrs
total 0 -r--r--r-- 1 root root 65536 Mar 5 19:38 highest_perf
-r--r--r-- 1 root root 65536 Mar 5 19:38 feedback_ctrs -r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_freq
-r--r--r-- 1 root root 65536 Mar 5 19:38 highest_perf -r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_nonlinear_perf
-r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_freq -r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_perf
-r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_nonlinear_perf -r--r--r-- 1 root root 65536 Mar 5 19:38 nominal_freq
-r--r--r-- 1 root root 65536 Mar 5 19:38 lowest_perf -r--r--r-- 1 root root 65536 Mar 5 19:38 nominal_perf
-r--r--r-- 1 root root 65536 Mar 5 19:38 nominal_freq -r--r--r-- 1 root root 65536 Mar 5 19:38 reference_perf
-r--r--r-- 1 root root 65536 Mar 5 19:38 nominal_perf -r--r--r-- 1 root root 65536 Mar 5 19:38 wraparound_time
-r--r--r-- 1 root root 65536 Mar 5 19:38 reference_perf
-r--r--r-- 1 root root 65536 Mar 5 19:38 wraparound_time
--------------------------------------------------------------------------------
* highest_perf : Highest performance of this processor (abstract scale). * highest_perf : Highest performance of this processor (abstract scale).
* nominal_perf : Highest sustained performance of this processor (abstract scale). * nominal_perf : Highest sustained performance of this processor
(abstract scale).
* lowest_nonlinear_perf : Lowest performance of this processor with nonlinear * lowest_nonlinear_perf : Lowest performance of this processor with nonlinear
power savings (abstract scale). power savings (abstract scale).
* lowest_perf : Lowest performance of this processor (abstract scale). * lowest_perf : Lowest performance of this processor (abstract scale).
@ -48,22 +51,26 @@ total 0
* feedback_ctrs : Includes both Reference and delivered performance counter. * feedback_ctrs : Includes both Reference and delivered performance counter.
Reference counter ticks up proportional to processor's reference performance. Reference counter ticks up proportional to processor's reference performance.
Delivered counter ticks up proportional to processor's delivered performance. Delivered counter ticks up proportional to processor's delivered performance.
* wraparound_time: Minimum time for the feedback counters to wraparound (seconds). * wraparound_time: Minimum time for the feedback counters to wraparound
(seconds).
* reference_perf : Performance level at which reference performance counter * reference_perf : Performance level at which reference performance counter
accumulates (abstract scale). accumulates (abstract scale).
--------------------------------------------------------------------------------
Computing Average Delivered Performance Computing Average Delivered Performance
=======================================
Below describes the steps to compute the average performance delivered by taking Below describes the steps to compute the average performance delivered by
two different snapshots of feedback counters at time T1 and T2. taking two different snapshots of feedback counters at time T1 and T2.
T1: Read feedback_ctrs as fbc_t1 T1: Read feedback_ctrs as fbc_t1
Wait or run some workload Wait or run some workload
T2: Read feedback_ctrs as fbc_t2
delivered_counter_delta = fbc_t2[del] - fbc_t1[del] T2: Read feedback_ctrs as fbc_t2
reference_counter_delta = fbc_t2[ref] - fbc_t1[ref]
delivered_perf = (refernce_perf x delivered_counter_delta) / reference_counter_delta ::
delivered_counter_delta = fbc_t2[del] - fbc_t1[del]
reference_counter_delta = fbc_t2[ref] - fbc_t1[ref]
delivered_perf = (refernce_perf x delivered_counter_delta) / reference_counter_delta

1
Documentation/admin-guide/acpi/index.rst
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@ -10,3 +10,4 @@ the Linux ACPI support.
initrd_table_override initrd_table_override
dsdt-override dsdt-override
cppc_sysfs