Re: [PATCH] Revert "cpufreq: schedutil: Don't restrict kthread to related_cpus unnecessarily"

[Viresh Kumar]

On 08-05-18, 08:33, Dietmar Eggemann wrote:
> This reverts commit e2cabe48c20efb174ce0c01190f8b9c5f3ea1d13.
> 
> Lifting the restriction that the sugov kthread is bound to the
> policy->related_cpus for a system with a slow switching cpufreq driver,
> which is able to perform DVFS from any cpu (e.g. cpufreq-dt), is not
> only not beneficial it also harms Enery-Aware Scheduling (EAS) on
> systems with asymmetric cpu capacities (e.g. Arm big.LITTLE).
> 
> The sugov kthread which does the update for the little cpus could
> potentially run on a big cpu. It could prevent that the big cluster goes
> into deeper idle states although all the tasks are running on the little
> cluster.

I think the original patch did the right thing, but that doesn't suit
everybody as you explained.

I wouldn't really revert the patch but fix my platform's cpufreq
driver to set dvfs_possible_from_any_cpu = false, so that other
platforms can still benefit from the original commit.

-- 
viresh