linux-kernel - Re: [RFC PATCH v1 5/8] sched/cpufreq_schedutil: always consider all CPUs when deciding next freq

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Message-ID: <20170711171834.7kldjsjg7utsc2jl@e106622-lin>
Date:   Tue, 11 Jul 2017 18:18:34 +0100
From:   Juri Lelli <juri.lelli@....com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     mingo@...hat.com, rjw@...ysocki.net, viresh.kumar@...aro.org,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        tglx@...utronix.de, vincent.guittot@...aro.org,
        rostedt@...dmis.org, luca.abeni@...tannapisa.it,
        claudio@...dence.eu.com, tommaso.cucinotta@...tannapisa.it,
        bristot@...hat.com, mathieu.poirier@...aro.org, tkjos@...roid.com,
        joelaf@...gle.com, andresoportus@...gle.com,
        morten.rasmussen@....com, dietmar.eggemann@....com,
        patrick.bellasi@....com, Ingo Molnar <mingo@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [RFC PATCH v1 5/8] sched/cpufreq_schedutil: always consider all
 CPUs when deciding next freq

On 11/07/17 18:17, Peter Zijlstra wrote:
> On Wed, Jul 05, 2017 at 09:59:02AM +0100, Juri Lelli wrote:
> >  		delta_ns = time - j_sg_cpu->last_update;
> >  		if (delta_ns > TICK_NSEC) {
> >  			j_sg_cpu->iowait_boost = 0;
> > -			continue;
> > +			j_sg_cpu->util_cfs = 0;
> 
> this is slighly confusing. Is this because we might not 'continue' with
> the new code?
> 

This is because, after TICK_NSEC, we only want to discard CFS
contribution and (yes) continue (so don't take into account
j_sg_cpu contribution) if DEADLINE contribution is zero as well.

> > +			if (j_sg_cpu->util_dl == 0)
> > +				continue;
> >  		}
> > +

With this change we might not continue if some DEADLINE utilization is
present for j_sg_cpu.

> >  		if (j_sg_cpu->flags & SCHED_CPUFREQ_RT)
> >  			return policy->cpuinfo.max_freq;
> >  
> > -- 
> > 2.11.0
> >