CPU frequency and voltage scaling statistics in the Linux(TM) kernel 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 - Venkatesh Pallipadi 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 interface (when configured) will appear in a separate directory under cpufreq in /sysfs (/devices/system/cpu/cpuX/cpufreq/stats/) for each CPU. Various statistics will form read_only files under this directory. This driver is designed to be independent of any particular cpufreq_driver 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 All the statistics will be from the time the stats driver has been inserted to the time when a read of a particular statistic is done. Obviously, stats driver will not have any information about the frequency transitions before the stats driver insertion. -------------------------------------------------------------------------------- :/sys/devices/system/cpu/cpu0/cpufreq/stats # ls -l total 0 drwxr-xr-x 2 root root 0 May 14 16:06 . 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 -------------------------------------------------------------------------------- - time_in_state This gives the amount of time spent in each of the frequencies supported by this CPU. The cat output will have "