cpufreq总概

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本文探讨了Linux中的CPU频率调整(CPufreq)框架，特别是Intel P-state驱动，重点介绍了stats接口如何跟踪各频率下运行时间和切换次数，以及P-state的含义和工作原理。通过实例展示了/sys/devices/system/cpu/cpu0/cpufreq/stats中的关键统计数据，如time_in_state和total_trans。

cpufreq 涉及到的模块

此图中，1）notifier此事物的影响。

stats

通过此接口可以看到每个频率运行的时间及调频的总次数。

在默认使用intel pstate的驱动时，看不到这些参数。

his gives the amount of time spent in each of the frequencies supported by
this CPU. The cat output will have "<frequency> <time>" pair in each line, which
will mean this CPU spent <time> usertime units of time at <frequency>. Output
will have one line for each of the supported frequencies. usertime units here
is 10mS (similar to other time exported in /proc).

<mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat time_in_state
3600000 2089
3400000 136
3200000 34
3000000 67
2800000 172488

- **total_trans**

This gives the total number of frequency transitions on this CPU. The cat
output will have a single count which is the total number of frequency
transitions.

<mysystem>:/sys/devices/system/cpu/cpu0/cpufreq/stats # cat total_trans
20