linux-kernel - Re: [PATCH 7/7 v2] sched/fair: Update overutilized detection

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Message-ID: <CAKfTPtDpWYy=QUdBqc8UCWOmjGt224BVC=L+fJpLe8Qcz9LYzQ@mail.gmail.com>
Date: Mon, 20 Jan 2025 16:50:38 +0100
From: Vincent Guittot <vincent.guittot@...aro.org>
To: Pierre Gondois <pierre.gondois@....com>
Cc: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com, 
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com, 
	mgorman@...e.de, vschneid@...hat.com, lukasz.luba@....com, 
	rafael.j.wysocki@...el.com, linux-kernel@...r.kernel.org, qyousef@...alina.io, 
	hongyan.xia2@....com, christian.loehle@....com, qperret@...gle.com
Subject: Re: [PATCH 7/7 v2] sched/fair: Update overutilized detection

On Fri, 17 Jan 2025 at 11:27, Pierre Gondois <pierre.gondois@....com> wrote:
>
> Hello Vincent,
>
> On 12/17/24 17:07, Vincent Guittot wrote:
> > Checking uclamp_min is useless and counterproductive for overutilized state
> > as misfit can now happen without being in overutilized state
>
> Before this patch a task was misfit if:
>    !task_fits_cpu(p, cpu)
> This is, if either:
> - task_util > 80% * CPU_capacity
> - task_UCLAMP_MIN > get_actual_cpu_capacity(cpu)
>
> A CPU was OU if:
>    !util_fits_cpu(cpu_util_cfs(cpu), rq_util_min, rq_util_max, cpu)
> This is:
> - CPU_util > 80% * CPU_capacity
>
> This should be the same after this patch. Just to be sure I understand correctly,
> this patch has no functional change and is independent from this serie right ?

yeah, I find it while running some functional tests on the patchset



>
> >
> > Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> > ---
> >   kernel/sched/fair.c | 5 ++---
> >   1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 9bddb094ee21..9eb4c4946ddc 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -6870,16 +6870,15 @@ static inline void hrtick_update(struct rq *rq)
> >   #ifdef CONFIG_SMP
> >   static inline bool cpu_overutilized(int cpu)
> >   {
> > -     unsigned long  rq_util_min, rq_util_max;
> > +     unsigned long rq_util_max;
> >
> >       if (!sched_energy_enabled())
> >               return false;
> >
> > -     rq_util_min = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MIN);
> >       rq_util_max = uclamp_rq_get(cpu_rq(cpu), UCLAMP_MAX);
> >
> >       /* Return true only if the utilization doesn't fit CPU's capacity */
> > -     return !util_fits_cpu(cpu_util_cfs(cpu), rq_util_min, rq_util_max, cpu);
> > +     return !util_fits_cpu(cpu_util_cfs(cpu), 0, rq_util_max, cpu);
> >   }
> >
> >   /*