Commit 3e57460f authored by Changbin Du's avatar Changbin Du Committed by Rafael J. Wysocki
Browse files

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



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

No essential content change.

Signed-off-by: default avatarChangbin Du <changbin.du@gmail.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 440ebec7

Documentation/acpi/cppc_sysfs.txt→Documentation/admin-guide/acpi/cppc_sysfs.rst

+39 −32
Original line number Diff line number Diff line 
.. SPDX-License-Identifier: GPL-2.0



==================================================

Collaborative Processor Performance Control (CPPC)

==================================================



CPPC

====



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
@@ -10,13 +16,11 @@ For more details on CPPC please refer to the ACPI specification at: 


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/



for each cpu X



--------------------------------------------------------------------------------

for each cpu X::



  $ ls -lR  /sys/devices/system/cpu/cpu0/acpi_cppc/

  /sys/devices/system/cpu/cpu0/acpi_cppc/:
@@ -31,10 +35,9 @@ total 0 
  -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).

* 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

  power savings (abstract scale).

* lowest_perf : Lowest performance of this processor (abstract scale).
@@ -48,21 +51,25 @@ total 0 
* feedback_ctrs : Includes both Reference and delivered performance counter.

  Reference counter ticks up proportional to processor's reference 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

  accumulates (abstract scale).



--------------------------------------------------------------------------------



Computing Average Delivered Performance

=======================================



Below describes the steps to compute the average performance delivered by taking

two different snapshots of feedback counters at time T1 and T2.

Below describes the steps to compute the average performance delivered by

taking two different snapshots of feedback counters at time T1 and T2.



  T1: Read feedback_ctrs as fbc_t1

      Wait or run some workload



  T2: Read feedback_ctrs as fbc_t2



::



  delivered_counter_delta = fbc_t2[del] - fbc_t1[del]

  reference_counter_delta = fbc_t2[ref] - fbc_t1[ref]

Documentation/admin-guide/acpi/index.rst

+1 −0
Original line number Diff line number Diff line
@@ -10,3 +10,4 @@ the Linux ACPI support. 


   initrd_table_override

   dsdt-override

   cppc_sysfs

CRA Git | Maintained and supported by SUSTech CRA and CCSE