1 .. SPDX-License-Identifier: GPL-2.0
2
3 ==========================================
4 General Description of sysfs CPUFreq Stats
5 ==========================================
6
7 information for users
8
9
10 Author: Venkatesh Pallipadi <venkatesh.pallipad
11
12 .. Contents
13
14 1. Introduction
15 2. Statistics Provided (with example)
16 3. Configuring cpufreq-stats
17
18
19 1. Introduction
20 ===============
21
22 cpufreq-stats is a driver that provides CPU fr
23 These statistics are provided in /sysfs as a b
24 interface (when configured) will appear in a s
25 in /sysfs (<sysfs root>/devices/system/cpu/cpu
26 Various statistics will form read_only files u
27
28 This driver is designed to be independent of a
29 that may be running on your CPU. So, it will w
30
31
32 2. Statistics Provided (with example)
33 =====================================
34
35 cpufreq stats provides following statistics (e
36
37 - time_in_state
38 - total_trans
39 - trans_table
40
41 All the statistics will be from the time the s
42 (or the time the stats were reset) to the time
43 statistic is done. Obviously, stats driver wil
44 about the frequency transitions before the sta
45
46 ::
47
48 <mysystem>:/sys/devices/system/cpu/cpu0/cp
49 total 0
50 drwxr-xr-x 2 root root 0 May 14 16:06
51 drwxr-xr-x 3 root root 0 May 14 15:58
52 --w------- 1 root root 4096 May 14 16:06
53 -r--r--r-- 1 root root 4096 May 14 16:06
54 -r--r--r-- 1 root root 4096 May 14 16:06
55 -r--r--r-- 1 root root 4096 May 14 16:06
56
57 - **reset**
58
59 Write-only attribute that can be used to reset
60 useful for evaluating system behaviour under d
61 need for a reboot.
62
63 - **time_in_state**
64
65 This gives the amount of time spent in each of
66 this CPU. The cat output will have "<frequency
67 will mean this CPU spent <time> usertime units
68 will have one line for each of the supported f
69 is 10mS (similar to other time exported in /pr
70
71 ::
72
73 <mysystem>:/sys/devices/system/cpu/cpu0/cp
74 3600000 2089
75 3400000 136
76 3200000 34
77 3000000 67
78 2800000 172488
79
80
81 - **total_trans**
82
83 This gives the total number of frequency trans
84 output will have a single count which is the t
85 transitions.
86
87 ::
88
89 <mysystem>:/sys/devices/system/cpu/cpu0/cp
90 20
91
92 - **trans_table**
93
94 This will give a fine grained information abou
95 transitions. The cat output here is a two dime
96 <i,j> (row i, column j) represents the count o
97 Freq_i to Freq_j. Freq_i rows and Freq_j colum
98 which the driver has provided the frequency ta
99 and so can be sorted (ascending or descending)
100 also contains the actual freq values for each
101 readability.
102
103 If the transition table is bigger than PAGE_SI
104 return an -EFBIG error.
105
106 ::
107
108 <mysystem>:/sys/devices/system/cpu/cpu0/cp
109 From : To
110 : 3600000 3400000 3200000
111 3600000: 0 5 0
112 3400000: 4 0 2
113 3200000: 0 1 0
114 3000000: 0 0 1
115 2800000: 0 0 0
116
117 3. Configuring cpufreq-stats
118 ============================
119
120 To configure cpufreq-stats in your kernel::
121
122 Config Main Menu
123 Power management options (ACPI
124 CPU Frequency scaling
125 [*] CPU Freque
126 [*] CPU freq
127
128
129 "CPU Frequency scaling" (CONFIG_CPU_FREQ) shou
130 cpufreq-stats.
131
132 "CPU frequency translation statistics" (CONFIG
133 statistics which includes time_in_state, total
134
135 Once this option is enabled and your CPU suppo
136 will be able to see the CPU frequency statisti
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