linux-kernel - Re: [PATCH 2/3] sched/fair: util

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Message-ID: <20180510153420.GG12217@hirez.programming.kicks-ass.net>
Date:   Thu, 10 May 2018 17:34:20 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Patrick Bellasi <patrick.bellasi@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Steve Muckle <smuckle@...gle.com>
Subject: Re: [PATCH 2/3] sched/fair: util_est: update before schedutil

On Thu, May 10, 2018 at 04:05:52PM +0100, Patrick Bellasi wrote:
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 1f6a23a5b451..01dfc47541e6 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5356,6 +5356,9 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
>  	struct cfs_rq *cfs_rq;
>  	struct sched_entity *se = &p->se;
>  
> +	/* Estimated utilization must be updated before schedutil */
> +	util_est_enqueue(&rq->cfs, p);

Please clarify the comment with a reason; because I'm sure that the next
time I see that comment, I'll go 'but why again!?'.

>  	/*
>  	 * If in_iowait is set, the code below may not trigger any cpufreq
>  	 * utilization updates, so do it here explicitly with the IOWAIT flag