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 S1752959AbdK3NMc (ORCPT <rfc822;w@1wt.eu>);
        Thu, 30 Nov 2017 08:12:32 -0500
Received: from mail-wm0-f66.google.com ([74.125.82.66]:42256 "EHLO
        mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1752904AbdK3NM2 (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 30 Nov 2017 08:12:28 -0500
X-Google-Smtp-Source: AGs4zMb/Vj/791XMy0O2RREAzWIcQHmyUoVq06Cjx4MykELRtqThulmB2Foj66QrL0BlGnlZ6lFNGg==
Date: Thu, 30 Nov 2017 14:12:22 +0100
From: Juri Lelli <juri.lelli@redhat.com>
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>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Morten Rasmussen <morten.rasmussen@arm.com>,
        Todd Kjos <tkjos@android.com>, Joel Fernandes <joelaf@google.com>
Subject: Re: [PATCH v3 1/6] cpufreq: schedutil: reset sg_cpus's flags at IDLE
 enter
Message-ID: <20171130131222.GA9903@localhost.localdomain>
References: <20171130114723.29210-1-patrick.bellasi@arm.com>
 <20171130114723.29210-2-patrick.bellasi@arm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20171130114723.29210-2-patrick.bellasi@arm.com>
User-Agent: Mutt/1.9.1 (2017-09-22)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi,

On 30/11/17 11:47, Patrick Bellasi wrote:

[...]

> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index 2f52ec0f1539..67339ccb5595 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -347,6 +347,12 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
>  
>  	sg_cpu->util = util;
>  	sg_cpu->max = max;
> +
> +	/* CPU is entering IDLE, reset flags without triggering an update */
> +	if (unlikely(flags & SCHED_CPUFREQ_IDLE)) {
> +		sg_cpu->flags = 0;
> +		goto done;
> +	}

Looks good for now. I'm just thinking that we will happen for DL, as a
CPU that still "has" a sleeping task is not going to be really idle
until the 0-lag time. I guess we could move this at that point in time?

>  	sg_cpu->flags = flags;
>  
>  	sugov_set_iowait_boost(sg_cpu, time, flags);
> @@ -361,6 +367,7 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
>  		sugov_update_commit(sg_policy, time, next_f);
>  	}
>  
> +done:
>  	raw_spin_unlock(&sg_policy->update_lock);
>  }
>  
> diff --git a/kernel/sched/idle_task.c b/kernel/sched/idle_task.c
> index d518664cce4f..6e8ae2aa7a13 100644
> --- a/kernel/sched/idle_task.c
> +++ b/kernel/sched/idle_task.c
> @@ -30,6 +30,10 @@ pick_next_task_idle(struct rq *rq, struct task_struct *prev, struct rq_flags *rf
>  	put_prev_task(rq, prev);
>  	update_idle_core(rq);
>  	schedstat_inc(rq->sched_goidle);
> +
> +	/* kick cpufreq (see the comment in kernel/sched/sched.h). */
> +	cpufreq_update_util(rq, SCHED_CPUFREQ_IDLE);

Don't know if it make things any cleaner, but you could add to the
comment that we don't actually trigger a frequency update with this
call.

Best,

Juri