- cpufreq: introduce hotplug governor
- The "hotplug" governor scales CPU frequency based on load, similar to
- "ondemand". It scales up to the highest frequency when "up_threshold"
- is crossed and scales down one frequency at a time when "down_threshold"
- is crossed. Unlike those governors, target frequencies are determined
- by directly accessing the CPUfreq frequency table, instead of taking
- some percentage of maximum available frequency.
- The key difference in the "hotplug" governor is that it will disable
- auxillary CPUs when the system is very idle, and enable them again once
- the system becomes busy. This is achieved by averaging load over
- multiple sampling periods; if CPUs were online or offlined based on a
- single sampling period then thrashing will occur.
- Sysfs entries exist for "hotplug_in_sampling_periods" and for
- "hotplug_out_sampling_periods" which determine how many consecutive
- periods get averaged to determine if auxillery CPUs should be onlined or
- offlined. Defaults are 5 periods and 20 periods respectively.
- Otherwise the standard sysfs entries you might find for "ondemand" and
- "conservative" governors are there.
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