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aadfa206 | 1 | .. SPDX-License-Identifier: GPL-2.0 |
21e3024c | 2 | |
aadfa206 MCC |
3 | ========================================== |
4 | General Description of sysfs CPUFreq Stats | |
5 | ========================================== | |
21e3024c | 6 | |
aadfa206 | 7 | information for users |
21e3024c | 8 | |
21e3024c | 9 | |
aadfa206 | 10 | Author: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> |
21e3024c | 11 | |
aadfa206 | 12 | .. Contents |
21e3024c | 13 | |
aadfa206 MCC |
14 | 1. Introduction |
15 | 2. Statistics Provided (with example) | |
16 | 3. Configuring cpufreq-stats | |
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17 | |
18 | ||
19 | 1. Introduction | |
aadfa206 | 20 | =============== |
21e3024c | 21 | |
a982ac06 | 22 | cpufreq-stats is a driver that provides CPU frequency statistics for each CPU. |
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23 | These statistics are provided in /sysfs as a bunch of read_only interfaces. This |
24 | interface (when configured) will appear in a separate directory under cpufreq | |
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25 | in /sysfs (<sysfs root>/devices/system/cpu/cpuX/cpufreq/stats/) for each CPU. |
26 | Various statistics will form read_only files under this directory. | |
27 | ||
28 | This driver is designed to be independent of any particular cpufreq_driver | |
29 | that may be running on your CPU. So, it will work with any cpufreq_driver. | |
30 | ||
31 | ||
32 | 2. Statistics Provided (with example) | |
aadfa206 | 33 | ===================================== |
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34 | |
35 | cpufreq stats provides following statistics (explained in detail below). | |
aadfa206 | 36 | |
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37 | - time_in_state |
38 | - total_trans | |
39 | - trans_table | |
40 | ||
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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 when a read of a particular | |
43 | statistic is done. Obviously, stats driver will not have any information | |
44 | about the frequency transitions before the stats driver insertion. | |
21e3024c | 45 | |
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46 | :: |
47 | ||
48 | <mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # ls -l | |
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 reset | |
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 total_trans | |
55 | -r--r--r-- 1 root root 4096 May 14 16:06 trans_table | |
56 | ||
57 | - **reset** | |
58 | ||
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59 | Write-only attribute that can be used to reset the stat counters. This can be |
60 | useful for evaluating system behaviour under different governors without the | |
61 | need for a reboot. | |
62 | ||
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63 | - **time_in_state** |
64 | ||
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65 | This gives the amount of time spent in each of the frequencies supported by |
66 | this CPU. The cat output will have "<frequency> <time>" pair in each line, which | |
67 | will mean this CPU spent <time> usertime units of time at <frequency>. Output | |
aadfa206 | 68 | will have one line for each of the supported frequencies. usertime units here |
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69 | is 10mS (similar to other time exported in /proc). |
70 | ||
aadfa206 | 71 | :: |
21e3024c | 72 | |
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73 | <mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat time_in_state |
74 | 3600000 2089 | |
75 | 3400000 136 | |
76 | 3200000 34 | |
77 | 3000000 67 | |
78 | 2800000 172488 | |
21e3024c | 79 | |
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80 | |
81 | - **total_trans** | |
82 | ||
83 | This gives the total number of frequency transitions on this CPU. The cat | |
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84 | output will have a single count which is the total number of frequency |
85 | transitions. | |
86 | ||
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87 | :: |
88 | ||
89 | <mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat total_trans | |
90 | 20 | |
91 | ||
92 | - **trans_table** | |
21e3024c | 93 | |
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94 | This will give a fine grained information about all the CPU frequency |
95 | transitions. The cat output here is a two dimensional matrix, where an entry | |
aadfa206 | 96 | <i,j> (row i, column j) represents the count of number of transitions from |
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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 table initially to the cpufreq core | |
99 | and so can be sorted (ascending or descending) or unsorted. The output here | |
100 | also contains the actual freq values for each row and column for better | |
101 | readability. | |
21e3024c | 102 | |
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103 | If the transition table is bigger than PAGE_SIZE, reading this will |
104 | return an -EFBIG error. | |
105 | ||
aadfa206 | 106 | :: |
21e3024c | 107 | |
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108 | <mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat trans_table |
109 | From : To | |
110 | : 3600000 3400000 3200000 3000000 2800000 | |
111 | 3600000: 0 5 0 0 0 | |
112 | 3400000: 4 0 2 0 0 | |
113 | 3200000: 0 1 0 2 0 | |
114 | 3000000: 0 0 1 0 3 | |
115 | 2800000: 0 0 0 2 0 | |
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116 | |
117 | 3. Configuring cpufreq-stats | |
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118 | ============================ |
119 | ||
120 | To configure cpufreq-stats in your kernel:: | |
21e3024c | 121 | |
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122 | Config Main Menu |
123 | Power management options (ACPI, APM) ---> | |
124 | CPU Frequency scaling ---> | |
125 | [*] CPU Frequency scaling | |
126 | [*] CPU frequency translation statistics | |
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127 | |
128 | ||
129 | "CPU Frequency scaling" (CONFIG_CPU_FREQ) should be enabled to configure | |
130 | cpufreq-stats. | |
131 | ||
132 | "CPU frequency translation statistics" (CONFIG_CPU_FREQ_STAT) provides the | |
7de962c0 | 133 | statistics which includes time_in_state, total_trans and trans_table. |
21e3024c | 134 | |
7de962c0 | 135 | Once this option is enabled and your CPU supports cpufrequency, you |
21e3024c | 136 | will be able to see the CPU frequency statistics in /sysfs. |