1 .. SPDX-License-Identifier: GPL-2.0 1 .. SPDX-License-Identifier: GPL-2.0
2 2
3 ========================================== 3 ==========================================
4 General Description of sysfs CPUFreq Stats 4 General Description of sysfs CPUFreq Stats
5 ========================================== 5 ==========================================
6 6
7 information for users 7 information for users
8 8
9 9
10 Author: Venkatesh Pallipadi <venkatesh.pallipad 10 Author: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
11 11
12 .. Contents 12 .. Contents
13 13
14 1. Introduction 14 1. Introduction
15 2. Statistics Provided (with example) 15 2. Statistics Provided (with example)
16 3. Configuring cpufreq-stats 16 3. Configuring cpufreq-stats
17 17
18 18
19 1. Introduction 19 1. Introduction
20 =============== 20 ===============
21 21
22 cpufreq-stats is a driver that provides CPU fr 22 cpufreq-stats is a driver that provides CPU frequency statistics for each CPU.
23 These statistics are provided in /sysfs as a b 23 These statistics are provided in /sysfs as a bunch of read_only interfaces. This
24 interface (when configured) will appear in a s 24 interface (when configured) will appear in a separate directory under cpufreq
25 in /sysfs (<sysfs root>/devices/system/cpu/cpu 25 in /sysfs (<sysfs root>/devices/system/cpu/cpuX/cpufreq/stats/) for each CPU.
26 Various statistics will form read_only files u 26 Various statistics will form read_only files under this directory.
27 27
28 This driver is designed to be independent of a 28 This driver is designed to be independent of any particular cpufreq_driver
29 that may be running on your CPU. So, it will w 29 that may be running on your CPU. So, it will work with any cpufreq_driver.
30 30
31 31
32 2. Statistics Provided (with example) 32 2. Statistics Provided (with example)
33 ===================================== 33 =====================================
34 34
35 cpufreq stats provides following statistics (e 35 cpufreq stats provides following statistics (explained in detail below).
36 36
37 - time_in_state 37 - time_in_state
38 - total_trans 38 - total_trans
39 - trans_table 39 - trans_table
40 40
41 All the statistics will be from the time the s 41 All the statistics will be from the time the stats driver has been inserted
42 (or the time the stats were reset) to the time 42 (or the time the stats were reset) to the time when a read of a particular
43 statistic is done. Obviously, stats driver wil 43 statistic is done. Obviously, stats driver will not have any information
44 about the frequency transitions before the sta 44 about the frequency transitions before the stats driver insertion.
45 45
46 :: 46 ::
47 47
48 <mysystem>:/sys/devices/system/cpu/cpu0/cp 48 <mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # ls -l
49 total 0 49 total 0
50 drwxr-xr-x 2 root root 0 May 14 16:06 50 drwxr-xr-x 2 root root 0 May 14 16:06 .
51 drwxr-xr-x 3 root root 0 May 14 15:58 51 drwxr-xr-x 3 root root 0 May 14 15:58 ..
52 --w------- 1 root root 4096 May 14 16:06 52 --w------- 1 root root 4096 May 14 16:06 reset
53 -r--r--r-- 1 root root 4096 May 14 16:06 53 -r--r--r-- 1 root root 4096 May 14 16:06 time_in_state
54 -r--r--r-- 1 root root 4096 May 14 16:06 54 -r--r--r-- 1 root root 4096 May 14 16:06 total_trans
55 -r--r--r-- 1 root root 4096 May 14 16:06 55 -r--r--r-- 1 root root 4096 May 14 16:06 trans_table
56 56
57 - **reset** 57 - **reset**
58 58
59 Write-only attribute that can be used to reset 59 Write-only attribute that can be used to reset the stat counters. This can be
60 useful for evaluating system behaviour under d 60 useful for evaluating system behaviour under different governors without the
61 need for a reboot. 61 need for a reboot.
62 62
63 - **time_in_state** 63 - **time_in_state**
64 64
65 This gives the amount of time spent in each of 65 This gives the amount of time spent in each of the frequencies supported by
66 this CPU. The cat output will have "<frequency 66 this CPU. The cat output will have "<frequency> <time>" pair in each line, which
67 will mean this CPU spent <time> usertime units 67 will mean this CPU spent <time> usertime units of time at <frequency>. Output
68 will have one line for each of the supported f 68 will have one line for each of the supported frequencies. usertime units here
69 is 10mS (similar to other time exported in /pr 69 is 10mS (similar to other time exported in /proc).
70 70
71 :: 71 ::
72 72
73 <mysystem>:/sys/devices/system/cpu/cpu0/cp 73 <mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat time_in_state
74 3600000 2089 74 3600000 2089
75 3400000 136 75 3400000 136
76 3200000 34 76 3200000 34
77 3000000 67 77 3000000 67
78 2800000 172488 78 2800000 172488
79 79
80 80
81 - **total_trans** 81 - **total_trans**
82 82
83 This gives the total number of frequency trans 83 This gives the total number of frequency transitions on this CPU. The cat
84 output will have a single count which is the t 84 output will have a single count which is the total number of frequency
85 transitions. 85 transitions.
86 86
87 :: 87 ::
88 88
89 <mysystem>:/sys/devices/system/cpu/cpu0/cp 89 <mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat total_trans
90 20 90 20
91 91
92 - **trans_table** 92 - **trans_table**
93 93
94 This will give a fine grained information abou 94 This will give a fine grained information about all the CPU frequency
95 transitions. The cat output here is a two dime 95 transitions. The cat output here is a two dimensional matrix, where an entry
96 <i,j> (row i, column j) represents the count o 96 <i,j> (row i, column j) represents the count of number of transitions from
97 Freq_i to Freq_j. Freq_i rows and Freq_j colum 97 Freq_i to Freq_j. Freq_i rows and Freq_j columns follow the sorting order in
98 which the driver has provided the frequency ta 98 which the driver has provided the frequency table initially to the cpufreq core
99 and so can be sorted (ascending or descending) 99 and so can be sorted (ascending or descending) or unsorted. The output here
100 also contains the actual freq values for each 100 also contains the actual freq values for each row and column for better
101 readability. 101 readability.
102 102
103 If the transition table is bigger than PAGE_SI 103 If the transition table is bigger than PAGE_SIZE, reading this will
104 return an -EFBIG error. 104 return an -EFBIG error.
105 105
106 :: 106 ::
107 107
108 <mysystem>:/sys/devices/system/cpu/cpu0/cp 108 <mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat trans_table
109 From : To 109 From : To
110 : 3600000 3400000 3200000 110 : 3600000 3400000 3200000 3000000 2800000
111 3600000: 0 5 0 111 3600000: 0 5 0 0 0
112 3400000: 4 0 2 112 3400000: 4 0 2 0 0
113 3200000: 0 1 0 113 3200000: 0 1 0 2 0
114 3000000: 0 0 1 114 3000000: 0 0 1 0 3
115 2800000: 0 0 0 115 2800000: 0 0 0 2 0
116 116
117 3. Configuring cpufreq-stats 117 3. Configuring cpufreq-stats
118 ============================ 118 ============================
119 119
120 To configure cpufreq-stats in your kernel:: 120 To configure cpufreq-stats in your kernel::
121 121
122 Config Main Menu 122 Config Main Menu
123 Power management options (ACPI 123 Power management options (ACPI, APM) --->
124 CPU Frequency scaling 124 CPU Frequency scaling --->
125 [*] CPU Freque 125 [*] CPU Frequency scaling
126 [*] CPU freq 126 [*] CPU frequency translation statistics
127 127
128 128
129 "CPU Frequency scaling" (CONFIG_CPU_FREQ) shou 129 "CPU Frequency scaling" (CONFIG_CPU_FREQ) should be enabled to configure
130 cpufreq-stats. 130 cpufreq-stats.
131 131
132 "CPU frequency translation statistics" (CONFIG 132 "CPU frequency translation statistics" (CONFIG_CPU_FREQ_STAT) provides the
133 statistics which includes time_in_state, total 133 statistics which includes time_in_state, total_trans and trans_table.
134 134
135 Once this option is enabled and your CPU suppo 135 Once this option is enabled and your CPU supports cpufrequency, you
136 will be able to see the CPU frequency statisti 136 will be able to see the CPU frequency statistics in /sysfs.
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