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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: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
authored by
Mauro Carvalho Chehab
and committed by
Rafael J. Wysocki
aadfa206
8f920589
+137
-127
+136
Documentation/cpu-freq/cpufreq-stats.rst
+136
Documentation/cpu-freq/cpufreq-stats.rst
···
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.. SPDX-License-Identifier: GPL-2.0
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==========================================
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General Description of sysfs CPUFreq Stats
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==========================================
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information for users
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Author: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
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.. Contents
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1. Introduction
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2. Statistics Provided (with example)
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3. Configuring cpufreq-stats
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1. Introduction
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===============
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cpufreq-stats is a driver that provides CPU frequency statistics for each CPU.
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These statistics are provided in /sysfs as a bunch of read_only interfaces. This
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interface (when configured) will appear in a separate directory under cpufreq
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in /sysfs (<sysfs root>/devices/system/cpu/cpuX/cpufreq/stats/) for each CPU.
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Various statistics will form read_only files under this directory.
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This driver is designed to be independent of any particular cpufreq_driver
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that may be running on your CPU. So, it will work with any cpufreq_driver.
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2. Statistics Provided (with example)
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=====================================
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cpufreq stats provides following statistics (explained in detail below).
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- time_in_state
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- total_trans
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- trans_table
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All the statistics will be from the time the stats driver has been inserted
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(or the time the stats were reset) to the time when a read of a particular
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statistic is done. Obviously, stats driver will not have any information
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about the frequency transitions before the stats driver insertion.
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::
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<mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # ls -l
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total 0
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drwxr-xr-x 2 root root 0 May 14 16:06 .
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drwxr-xr-x 3 root root 0 May 14 15:58 ..
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--w------- 1 root root 4096 May 14 16:06 reset
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-r--r--r-- 1 root root 4096 May 14 16:06 time_in_state
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-r--r--r-- 1 root root 4096 May 14 16:06 total_trans
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-r--r--r-- 1 root root 4096 May 14 16:06 trans_table
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- **reset**
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Write-only attribute that can be used to reset the stat counters. This can be
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useful for evaluating system behaviour under different governors without the
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need for a reboot.
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- **time_in_state**
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This gives the amount of time spent in each of the frequencies supported by
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this CPU. The cat output will have "<frequency> <time>" pair in each line, which
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will mean this CPU spent <time> usertime units of time at <frequency>. Output
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will have one line for each of the supported frequencies. usertime units here
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is 10mS (similar to other time exported in /proc).
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::
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<mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat time_in_state
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3600000 2089
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3400000 136
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3200000 34
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3000000 67
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2800000 172488
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- **total_trans**
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This gives the total number of frequency transitions on this CPU. The cat
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output will have a single count which is the total number of frequency
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transitions.
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::
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<mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat total_trans
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20
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- **trans_table**
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This will give a fine grained information about all the CPU frequency
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transitions. The cat output here is a two dimensional matrix, where an entry
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<i,j> (row i, column j) represents the count of number of transitions from
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Freq_i to Freq_j. Freq_i rows and Freq_j columns follow the sorting order in
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which the driver has provided the frequency table initially to the cpufreq core
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and so can be sorted (ascending or descending) or unsorted. The output here
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also contains the actual freq values for each row and column for better
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readability.
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If the transition table is bigger than PAGE_SIZE, reading this will
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return an -EFBIG error.
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::
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<mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat trans_table
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From : To
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: 3600000 3400000 3200000 3000000 2800000
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3600000: 0 5 0 0 0
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3400000: 4 0 2 0 0
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3200000: 0 1 0 2 0
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3000000: 0 0 1 0 3
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2800000: 0 0 0 2 0
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3. Configuring cpufreq-stats
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============================
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To configure cpufreq-stats in your kernel::
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Config Main Menu
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Power management options (ACPI, APM) --->
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CPU Frequency scaling --->
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[*] CPU Frequency scaling
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[*] CPU frequency translation statistics
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"CPU Frequency scaling" (CONFIG_CPU_FREQ) should be enabled to configure
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cpufreq-stats.
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"CPU frequency translation statistics" (CONFIG_CPU_FREQ_STAT) provides the
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statistics which includes time_in_state, total_trans and trans_table.
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Once this option is enabled and your CPU supports cpufrequency, you
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will be able to see the CPU frequency statistics in /sysfs.
-127
Documentation/cpu-freq/cpufreq-stats.txt
-127
Documentation/cpu-freq/cpufreq-stats.txt
···
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CPU frequency and voltage scaling statistics in the Linux(TM) kernel
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L i n u x c p u f r e q - s t a t s d r i v e r
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- information for users -
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Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
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-
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Contents
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-
1. Introduction
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-
2. Statistics Provided (with example)
15
-
3. Configuring cpufreq-stats
16
-
17
-
18
-
1. Introduction
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-
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-
cpufreq-stats is a driver that provides CPU frequency statistics for each CPU.
21
-
These statistics are provided in /sysfs as a bunch of read_only interfaces. This
22
-
interface (when configured) will appear in a separate directory under cpufreq
23
-
in /sysfs (<sysfs root>/devices/system/cpu/cpuX/cpufreq/stats/) for each CPU.
24
-
Various statistics will form read_only files under this directory.
25
-
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-
This driver is designed to be independent of any particular cpufreq_driver
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-
that may be running on your CPU. So, it will work with any cpufreq_driver.
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-
29
-
30
-
2. Statistics Provided (with example)
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-
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-
cpufreq stats provides following statistics (explained in detail below).
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-
- time_in_state
34
-
- total_trans
35
-
- trans_table
36
-
37
-
All the statistics will be from the time the stats driver has been inserted
38
-
(or the time the stats were reset) to the time when a read of a particular
39
-
statistic is done. Obviously, stats driver will not have any information
40
-
about the frequency transitions before the stats driver insertion.
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-
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--------------------------------------------------------------------------------
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<mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # ls -l
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total 0
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drwxr-xr-x 2 root root 0 May 14 16:06 .
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drwxr-xr-x 3 root root 0 May 14 15:58 ..
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--w------- 1 root root 4096 May 14 16:06 reset
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-r--r--r-- 1 root root 4096 May 14 16:06 time_in_state
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-r--r--r-- 1 root root 4096 May 14 16:06 total_trans
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-r--r--r-- 1 root root 4096 May 14 16:06 trans_table
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--------------------------------------------------------------------------------
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-
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- reset
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-
Write-only attribute that can be used to reset the stat counters. This can be
55
-
useful for evaluating system behaviour under different governors without the
56
-
need for a reboot.
57
-
58
-
- time_in_state
59
-
This gives the amount of time spent in each of the frequencies supported by
60
-
this CPU. The cat output will have "<frequency> <time>" pair in each line, which
61
-
will mean this CPU spent <time> usertime units of time at <frequency>. Output
62
-
will have one line for each of the supported frequencies. usertime units here
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-
is 10mS (similar to other time exported in /proc).
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-
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--------------------------------------------------------------------------------
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<mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat time_in_state
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3600000 2089
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3400000 136
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3200000 34
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3000000 67
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-
2800000 172488
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--------------------------------------------------------------------------------
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-
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- total_trans
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This gives the total number of frequency transitions on this CPU. The cat
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output will have a single count which is the total number of frequency
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transitions.
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-
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--------------------------------------------------------------------------------
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<mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat total_trans
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--------------------------------------------------------------------------------
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- trans_table
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This will give a fine grained information about all the CPU frequency
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transitions. The cat output here is a two dimensional matrix, where an entry
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-
<i,j> (row i, column j) represents the count of number of transitions from
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-
Freq_i to Freq_j. Freq_i rows and Freq_j columns follow the sorting order in
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-
which the driver has provided the frequency table initially to the cpufreq core
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-
and so can be sorted (ascending or descending) or unsorted. The output here
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-
also contains the actual freq values for each row and column for better
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-
readability.
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-
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-
If the transition table is bigger than PAGE_SIZE, reading this will
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return an -EFBIG error.
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-
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--------------------------------------------------------------------------------
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<mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat trans_table
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From : To
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: 3600000 3400000 3200000 3000000 2800000
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3600000: 0 5 0 0 0
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3400000: 4 0 2 0 0
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3200000: 0 1 0 2 0
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3000000: 0 0 1 0 3
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2800000: 0 0 0 2 0
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--------------------------------------------------------------------------------
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3. Configuring cpufreq-stats
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To configure cpufreq-stats in your kernel
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Config Main Menu
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-
Power management options (ACPI, APM) --->
115
-
CPU Frequency scaling --->
116
-
[*] CPU Frequency scaling
117
-
[*] CPU frequency translation statistics
118
-
119
-
120
-
"CPU Frequency scaling" (CONFIG_CPU_FREQ) should be enabled to configure
121
-
cpufreq-stats.
122
-
123
-
"CPU frequency translation statistics" (CONFIG_CPU_FREQ_STAT) provides the
124
-
statistics which includes time_in_state, total_trans and trans_table.
125
-
126
-
Once this option is enabled and your CPU supports cpufrequency, you
127
-
will be able to see the CPU frequency statistics in /sysfs.