linux-kernel - Re: [PATCH] sched/fair: Rearrange select_task_rq

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Date:   Wed, 25 Apr 2018 09:12:04 +0100
From:   Quentin Perret <quentin.perret@....com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Valentin Schneider <valentin.schneider@....com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Ingo Molnar <mingo@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        linux-kernel@...r.kernel.org, c@...ez.programming.kicks-ass.net
Subject: Re: [PATCH] sched/fair: Rearrange select_task_rq_fair() to optimize
 it

On Tuesday 24 Apr 2018 at 14:35:23 (+0200), Peter Zijlstra wrote:
> On Tue, Apr 24, 2018 at 12:19:07PM +0100, Valentin Schneider wrote:
> > On 24/04/18 11:43, Peter Zijlstra wrote:
> > > On Tue, Apr 24, 2018 at 11:02:26AM +0100, Valentin Schneider wrote:
> > >> I'd argue making things easier to read is a non-negligible part as well.
> > > 
> > > Right, so I don't object to either of these (I think); but it would be
> > > good to see this in combination with that proposed EAS change.
> > > 
> > 
> > True, I would've said the call to find_energy_efficient_cpu() ([1]) could
> > simply be added to the if (sd) {} case, but...
> 
> I think the proposal was to put it before the for_each_domain() loop
> entirely, however...
> 
> > > I think you (valentin) wanted to side-step the entire domain loop in
> > > that case or something.
> > > 
> > 
> > ...this would change more things. Admittedly I've been sort of out of the loop
> > (no pun intended) lately, but this doesn't ring a bell. That might have been
> > the other frenchie (Quentin) :)
> 
> It does indeed appear I confused the two of you, it was Quentin playing
> with that.
> 
> In any case, if there not going to be conflicts here, this all looks
> good.

So, the proposal was to re-use the loop to find a non-overutilized sched
domain in which we can use EAS. But yes, I don't see why this would
conflict with this patch so I don't have objections against it.

Thanks,
Quentin