Re: [PATCH 2/3] sched/fair: util_est: update before schedutil

From: Peter Zijlstra <peterz@infradead.org>
To: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
	Ingo Molnar <mingo@redhat.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Morten Rasmussen <morten.rasmussen@arm.com>,
	Juri Lelli <juri.lelli@redhat.com>,
	Joel Fernandes <joelaf@google.com>,
	Steve Muckle <smuckle@google.com>
Subject: Re: [PATCH 2/3] sched/fair: util_est: update before schedutil
Date: Thu, 10 May 2018 17:34:20 +0200	[thread overview]
Message-ID: <20180510153420.GG12217@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20180510150553.28122-3-patrick.bellasi@arm.com>

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