linux-kernel - Re: [PATCH v2] sched: Consolidate cpufreq updates

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Date: Mon, 13 May 2024 10:50:21 +0200
From: Vincent Guittot <vincent.guittot@...aro.org>
To: Qais Yousef <qyousef@...alina.io>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, Viresh Kumar <viresh.kumar@...aro.org>, 
	Ingo Molnar <mingo@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Juri Lelli <juri.lelli@...hat.com>, Steven Rostedt <rostedt@...dmis.org>, 
	Dietmar Eggemann <dietmar.eggemann@....com>, Ben Segall <bsegall@...gle.com>, 
	Mel Gorman <mgorman@...e.de>, Daniel Bristot de Oliveira <bristot@...hat.com>, 
	Valentin Schneider <vschneid@...hat.com>, Christian Loehle <christian.loehle@....com>, linux-pm@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] sched: Consolidate cpufreq updates

On Sat, 11 May 2024 at 04:03, Qais Yousef <qyousef@...alina.io> wrote:
>
> On 05/07/24 14:53, Vincent Guittot wrote:
>
> > No I mean going out of idle. On an idle cpu, nothing happens at CFS
> > task wakeup and we have to wait for the next tick to apply the new
> > freq. This happens for both short task with uclamp min or long
> > running/sleeping task (i.e. with high util_est)
>
> I think I found the problem, thanks for catching it!

Ok I will test it when I will be back and have access to the board

>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index cbe79c8ac2ed..dea9383a906e 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4714,7 +4714,7 @@ static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
>         if (se->avg.last_update_time && !(flags & SKIP_AGE_LOAD))
>                 __update_load_avg_se(now, cfs_rq, se);
>
> -       cfs_rq->decayed  = update_cfs_rq_load_avg(now, cfs_rq);
> +       cfs_rq->decayed |= update_cfs_rq_load_avg(now, cfs_rq);
>         cfs_rq->decayed |= propagate_entity_load_avg(se);
>
>         if (!se->avg.last_update_time && (flags & DO_ATTACH)) {