linux-kernel - Re: [PATCH v6 09/16] sched/cpufreq: uclamp: Add utilization clamping for RT tasks

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Date:   Tue, 22 Jan 2019 12:37:04 +0000
From:   Patrick Bellasi <patrick.bellasi@....com>
To:     Quentin Perret <quentin.perret@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-api@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tejun Heo <tj@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Paul Turner <pjt@...gle.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Todd Kjos <tkjos@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Steve Muckle <smuckle@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>
Subject: Re: [PATCH v6 09/16] sched/cpufreq: uclamp: Add utilization clamping
 for RT tasks

On 22-Jan 12:30, Quentin Perret wrote:
> On Tuesday 15 Jan 2019 at 10:15:06 (+0000), Patrick Bellasi wrote:
> > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> > index 520ee2b785e7..38a05a4f78cc 100644
> > --- a/kernel/sched/cpufreq_schedutil.c
> > +++ b/kernel/sched/cpufreq_schedutil.c
> > @@ -201,9 +201,6 @@ unsigned long schedutil_freq_util(int cpu, unsigned long util_cfs,
> >  	unsigned long dl_util, util, irq;
> >  	struct rq *rq = cpu_rq(cpu);
> >  
> > -	if (type == FREQUENCY_UTIL && rt_rq_is_runnable(&rq->rt))
> > -		return max;
> > -
> >  	/*
> >  	 * Early check to see if IRQ/steal time saturates the CPU, can be
> >  	 * because of inaccuracies in how we track these -- see
> > @@ -219,15 +216,19 @@ unsigned long schedutil_freq_util(int cpu, unsigned long util_cfs,
> >  	 * utilization (PELT windows are synchronized) we can directly add them
> >  	 * to obtain the CPU's actual utilization.
> >  	 *
> > -	 * CFS utilization can be boosted or capped, depending on utilization
> > -	 * clamp constraints requested by currently RUNNABLE tasks.
> > +	 * CFS and RT utilization can be boosted or capped, depending on
> > +	 * utilization clamp constraints requested by currently RUNNABLE
> > +	 * tasks.
> >  	 * When there are no CFS RUNNABLE tasks, clamps are released and
> >  	 * frequency will be gracefully reduced with the utilization decay.
> >  	 */
> > -	util = (type == ENERGY_UTIL)
> > -		? util_cfs
> > -		: uclamp_util(rq, util_cfs);
> > -	util += cpu_util_rt(rq);
> > +	util = cpu_util_rt(rq);
> > +	if (type == FREQUENCY_UTIL) {
> > +		util += cpu_util_cfs(rq);
> > +		util  = uclamp_util(rq, util);
> 
> So with this we don't go to max to anymore for CONFIG_UCLAMP_TASK=n no ?

Mmm... good point!

I need to guard this chagen for the !CONFIG_UCLAMP_TASK case!

> 
> Thanks,
> Quentin

Cheers Patrick

-- 
#include <best/regards.h>

Patrick Bellasi