linux-kernel - Re: [RFC PATCH v4 08/12] sched: Add over-utilization/tipping point indicator

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Message-ID: <20180706113208.GS2458@hirez.programming.kicks-ass.net>
Date:   Fri, 6 Jul 2018 13:32:08 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Quentin Perret <quentin.perret@....com>
Cc:     rjw@...ysocki.net, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, gregkh@...uxfoundation.org,
        mingo@...hat.com, dietmar.eggemann@....com,
        morten.rasmussen@....com, chris.redpath@....com,
        patrick.bellasi@....com, valentin.schneider@....com,
        vincent.guittot@...aro.org, thara.gopinath@...aro.org,
        viresh.kumar@...aro.org, tkjos@...gle.com, joel@...lfernandes.org,
        smuckle@...gle.com, adharmap@...cinc.com, skannan@...cinc.com,
        pkondeti@...eaurora.org, juri.lelli@...hat.com,
        edubezval@...il.com, srinivas.pandruvada@...ux.intel.com,
        currojerez@...eup.net, javi.merino@...nel.org
Subject: Re: [RFC PATCH v4 08/12] sched: Add over-utilization/tipping point
 indicator

On Thu, Jun 28, 2018 at 12:40:39PM +0100, Quentin Perret wrote:
> @@ -5384,6 +5402,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
>  {
>  	struct cfs_rq *cfs_rq;
>  	struct sched_entity *se = &p->se;
> +	int task_new = !(flags & ENQUEUE_WAKEUP);
>  
>  	/*
>  	 * The code below (indirectly) updates schedutil which looks at
> @@ -5431,8 +5450,12 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
>  		update_cfs_group(se);
>  	}
>  
> -	if (!se)
> +	if (!se) {
>  		add_nr_running(rq, 1);
> +		if (!task_new)
> +			update_overutilized_status(rq);

I'm confused... why only for !ENQUEUE_WAKEUP and why use a local
variable for something that's used only once?

> +	}
>  
>  	hrtick_update(rq);
>  }