Re: [PATCH] sched/fair: Speed-up energy-aware wake-ups

[Quentin Perret]

Hi Pavan,

On Friday 20 Sep 2019 at 08:32:15 (+0530), Pavan Kondeti wrote:
> Earlier, we are not checking the spare capacity for the prev_cpu. Now that the
> continue statement is removed, prev_cpu could also be the max_spare_cap_cpu.
> Actually that makes sense. Because there is no reason why we want to select
> another CPU which has less spare capacity than previous CPU.
> 
> Is this behavior intentional?

The intent was indeed to not compute the energy for another CPU in
prev_cpu's perf domain if prev_cpu is the one with max spare cap -- it
is useless to do so since this other CPU cannot 'beat' prev_cpu and
will never be chosen in the end.

But I did miss that we'd end up computing the energy for prev_cpu
twice ... Harmless but useless. So yeah, let's optimize that case too :)

> When prev_cpu == max_spare_cap_cpu, we are evaluating the energy again for the
> same CPU below. That could have been skipped by returning prev_cpu when
> prev_cpu == max_spare_cap_cpu.

Right, something like the patch below ? My test results are still
looking good with it applied.

Thanks for the careful review,
Quentin
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