Commit aadfa206 authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab Committed by Rafael J. Wysocki
Browse files

docs: cpu-freq: convert cpufreq-stats.txt to ReST 



- Add a SPDX header;
- Add a document title, based on the original contents of
  cpu-freq/index.txt;
- Use lists where needed;
- Comment out the existing text-only index;
- Adjust some title marks;
- Use bold on some places;
- Mark literal blocks as such;
- Some whitespace fixes and new line breaks;
- Add it to cpu-freq/index.rst.

Signed-off-by: default avatarMauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 8f920589

Documentation/cpu-freq/cpufreq-stats.txt→Documentation/cpu-freq/cpufreq-stats.rst

+64 −55
Original line number Diff line number Diff line 
.. SPDX-License-Identifier: GPL-2.0



     CPU frequency and voltage scaling statistics in the Linux(TM) kernel

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

General Description of sysfs CPUFreq Stats

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



information for users



             L i n u x    c p u f r e q - s t a t s   d r i v e r



                       - information for users -

Author: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>



.. Contents



             Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>



Contents

   1. Introduction

   2. Statistics Provided (with example)

   3. Configuring cpufreq-stats





1. Introduction

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



cpufreq-stats is a driver that provides CPU frequency statistics for each CPU.

These statistics are provided in /sysfs as a bunch of read_only interfaces. This
@@ -28,8 +30,10 @@ that may be running on your CPU. So, it will work with any cpufreq_driver. 




2. Statistics Provided (with example)

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



cpufreq stats provides following statistics (explained in detail below).



-  time_in_state

-  total_trans

-  trans_table
@@ -39,7 +43,8 @@ All the statistics will be from the time the stats driver has been inserted 
statistic is done. Obviously, stats driver will not have any information

about the frequency transitions before the stats driver insertion.



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

::



    <mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # ls -l

    total 0

    drwxr-xr-x  2 root root    0 May 14 16:06 .
@@ -48,41 +53,44 @@ drwxr-xr-x 3 root root 0 May 14 15:58 .. 
    -r--r--r--  1 root root 4096 May 14 16:06 time_in_state

    -r--r--r--  1 root root 4096 May 14 16:06 total_trans

    -r--r--r--  1 root root 4096 May 14 16:06 trans_table

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



-  reset

- **reset**



Write-only attribute that can be used to reset the stat counters. This can be

useful for evaluating system behaviour under different governors without the

need for a reboot.



-  time_in_state

- **time_in_state**



This gives the amount of time spent in each of the frequencies supported by

this CPU. The cat output will have "<frequency> <time>" pair in each line, which

will mean this CPU spent <time> usertime units of time at <frequency>. Output

will have one line for each of the supported frequencies. usertime units here

is 10mS (similar to other time exported in /proc).



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

::



    <mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat time_in_state

    3600000 2089

    3400000 136

    3200000 34

    3000000 67

    2800000 172488

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





-  total_trans

- **total_trans**



This gives the total number of frequency transitions on this CPU. The cat

output will have a single count which is the total number of frequency

transitions.



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

::



    <mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat total_trans

    20

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



-  trans_table

- **trans_table**



This will give a fine grained information about all the CPU frequency

transitions. The cat output here is a two dimensional matrix, where an entry

<i,j> (row i, column j) represents the count of number of transitions from
@@ -95,7 +103,8 @@ readability. 
If the transition table is bigger than PAGE_SIZE, reading this will

return an -EFBIG error.



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

::



    <mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat trans_table

    From  :    To

	    :   3600000   3400000   3200000   3000000   2800000
@@ -104,12 +113,12 @@ return an -EFBIG error. 
    3200000:         0         1         0         2         0

    3000000:         0         0         1         0         3

    2800000:         0         0         0         2         0

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





3. Configuring cpufreq-stats

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



To configure cpufreq-stats in your kernel::



To configure cpufreq-stats in your kernel

	Config Main Menu

		Power management options (ACPI, APM)  --->

			CPU Frequency scaling  --->

Documentation/cpu-freq/index.rst

+1 −0
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ Author: Dominik Brodowski <linux@brodo.de> 


   core

   cpu-drivers

   cpufreq-stats



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