本文介绍Linux系统中CPU频率动态调整的工作原理。包括核心代码位置、sysfs用户空间接口、频率策略结构、频率调整策略实现单元(governor)及其实现方式等内容。
Linux CPUFreq is the frequency dynamically change lib.
1. the code is at linux/driver/cpufreq/
2. the sysfs user space interface is at /sys/devices/system/cpu/ . User could switch governor and set frequency range here.
3.each CPU has frequency policy structure object. CPU could share it. Policy contains frequency range setting.
4.frequency policy object connect to governor which is the real policy implementing unit.
5.governor 'ondemand' has a work queue, which calculate the CPU loading and then decide to change the frequency.
6.governor call cpufreq_driver->target() or target_index() to change the hardware clock setting.
7.voltage change is related to frequency change.
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