linux-kernel - Re: [PATCH v4 1/2] sched/fair: Check a task has a fitting cpu when updating misfit

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Date: Wed, 24 Jan 2024 22:46:16 +0000
From: Qais Yousef <qyousef@...alina.io>
To: Vincent Guittot <vincent.guittot@...aro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@....com>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org,
	Pierre Gondois <Pierre.Gondois@....com>
Subject: Re: [PATCH v4 1/2] sched/fair: Check a task has a fitting cpu when
 updating misfit

On 01/23/24 09:32, Vincent Guittot wrote:

> > > @@ -9583,9 +9630,7 @@ check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
> > >   */
> > >  static inline int check_misfit_status(struct rq *rq, struct sched_domain *sd)
> > >  {
> > > -     return rq->misfit_task_load &&
> > > -             (arch_scale_cpu_capacity(rq->cpu) < rq->rd->max_cpu_capacity ||
> > > -              check_cpu_capacity(rq, sd));
> > > +     return rq->misfit_task_load && check_cpu_capacity(rq, sd);
> >
> > You removed 'arch_scale_cpu_capacity(rq->cpu) <
> > rq->rd->max_cpu_capacity' here. Why? I can see that with the standard
> > setup (max CPU capacity equal 1024) which is what we probably use 100%
> > of the time now. It might get useful again when Vincent will introduce
> > his 'user space system pressure' implementation?
> 
> That's interesting because I'm doing the opposite in the user space
> system pressure that I'm preparing:
> I keep something similar to (arch_scale_cpu_capacity(rq->cpu) <
> rq->rd->max_cpu_capacity but I remove check_cpu_capacity(rq, sd) which
> seems to be useless because it's already used earlier in
> nohz_balancer_kick()

Okay. I need to look at your patches anyway. I can potentially rebase on top of
your series.


Cheers

--
Qais Yousef