linux-kernel - Re: [PATCH v3 0/6] cpufreq: schedutil: fixes for flags updates

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Date:   Fri, 22 Dec 2017 12:25:30 +0000
From:   Patrick Bellasi <patrick.bellasi@....com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Juri Lelli <juri.lelli@...hat.com>, 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>,
        Todd Kjos <tkjos@...roid.com>,
        Joel Fernandes <joelaf@...gle.com>
Subject: Re: [PATCH v3 0/6] cpufreq: schedutil: fixes for flags updates

On 22-Dec 13:10, Peter Zijlstra wrote:
> On Fri, Dec 22, 2017 at 12:46:18PM +0100, Peter Zijlstra wrote:
> > Blergh that'd make a mess of things again.
> 
> Something like so then..
> 
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -187,11 +187,16 @@ static void sugov_get_util(struct sugov_
>  
>  static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu)
>  {
> -	unsigned long util = sg_cpu->util_cfs + sg_cpu->util_dl;
>  	struct rq *rq = cpu_rq(sg_cpu->cpu);
> +	unsigned long util;
>  
> -	if (rq->rt.rt_nr_running)
> +	if (rq->rt.rt_nr_running) {
>  		util = sg_cpu->max;
> +	} else {
> +		util = sg_cpu->util_dl;
> +		if (rq->cfs.h_nr_running)
> +			util += sg_cpu->util_cfs;

Since sugov_aggregate_util always follow sugov_get_util, maybe we
can move these checks into the latter and remove the first one?

That way, sg_cpu->util_{dl,rt,cfs} will always report exactly the
requests of each class considering also which tasks are RUNNABLE at
sugov_get_util time.

Still the observation of Juri is valid: do we wanna really disregard
all the CFS blocked load as soon as there are not CFS tasks?

> +	}
>  
>  	/*
>  	 * Ideally we would like to set util_dl as min/guaranteed freq and

-- 
#include <best/regards.h>

Patrick Bellasi