Re: [PATCH] cpuidle: Add "cpuidle.use_deepest" to bypass governor and allow HW to go deep

[Thomas Ilsche]

On 2017-11-09 08:38, Len Brown wrote:
> From: Len Brown <len.brown@xxxxxxxxx>
>
> While there are several mechanisms (cmdline, sysfs, PM_QOS) to limit
> cpuidle to shallow idle states, there is no simple mechanism
> to give the hardware permission to enter the deeptest state permitted by PM_QOS.
>
> Here we create the "cpuidle.use_deepest" modparam to provide this capability.
>
> "cpuidle.use_deepest=Y" can be set at boot-time, and
> /sys/module/cpuidle/use_deepest can be modified (with Y/N) at run-time.

This is a good option to have and can conveniently prevent idle power consumption
issues. But that wouldn't be a reasonable default, would it?
I still think there is an inherent need for a heuristic and a corresponding
mitigation to avoid staying in a sleep state too long.

Best,
Thomas