From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1752491AbeEKFoo (ORCPT <rfc822;w@1wt.eu>);
        Fri, 11 May 2018 01:44:44 -0400
Received: from mail-pf0-f195.google.com ([209.85.192.195]:33386 "EHLO
        mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751947AbeEKFom (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 11 May 2018 01:44:42 -0400
X-Google-Smtp-Source: AB8JxZq7GhOpoZmywOj+Tc9bof16i6gbsYQylh/VQM/WPrtDZpmzNZTdiCGxvRl/9Xm6kpWNv4G8Fg==
Date: Fri, 11 May 2018 11:14:39 +0530
From: Viresh Kumar <viresh.kumar@linaro.org>
To: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
        Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        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
Message-ID: <20180511054439.slrpscgm6ivho5qy@vireshk-i7>
References: <20180510150553.28122-1-patrick.bellasi@arm.com>
 <20180510150553.28122-3-patrick.bellasi@arm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20180510150553.28122-3-patrick.bellasi@arm.com>
User-Agent: NeoMutt/20180323-120-3dd1ac
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 10-05-18, 16:05, Patrick Bellasi wrote:
> When a task is enqueue the estimated utilization of a CPU is updated
> to better support the selection of the required frequency.
> However, schedutil is (implicitly) updated by update_load_avg() which
> always happens before util_est_{en,de}queue(), thus potentially
> introducing a latency between estimated utilization updates and
> frequency selections.
> 
> Let's update util_est at the beginning of enqueue_task_fair(),
> which will ensure that all schedutil updates will see the most
> updated estimated utilization value for a CPU.
> 
> Reported-by: Vincent Guittot <vincent.guittot@linaro.org>
> Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Vincent Guittot <vincent.guittot@linaro.org>
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-pm@vger.kernel.org
> ---
>  kernel/sched/fair.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)

Fixes and Stable ?

> 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);
> +
>  	/*
>  	 * If in_iowait is set, the code below may not trigger any cpufreq
>  	 * utilization updates, so do it here explicitly with the IOWAIT flag
> @@ -5397,7 +5400,6 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
>  	if (!se)
>  		add_nr_running(rq, 1);
>  
> -	util_est_enqueue(&rq->cfs, p);
>  	hrtick_update(rq);
>  }

Acked-by: Viresh Kumar <viresh.kumar@linaro.org>

-- 
viresh