linux-kernel - Re: [PATCH V2 1/2] sched/core: Rename and move schedutil_cpu

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Date:   Fri, 23 Oct 2020 16:24:52 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        linux-kernel@...r.kernel.org, Quentin Perret <qperret@...gle.com>,
        Lukasz Luba <lukasz.luba@....com>, linux-pm@...r.kernel.org
Subject: Re: [PATCH V2 1/2] sched/core: Rename and move schedutil_cpu_util()
 to core.c

On 23-10-20, 12:34, Peter Zijlstra wrote:
> On Fri, Oct 23, 2020 at 03:50:20PM +0530, Viresh Kumar wrote:
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index d2003a7d5ab5..369ff54d11d4 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -5117,6 +5117,119 @@ struct task_struct *idle_task(int cpu)
> >  	return cpu_rq(cpu)->idle;
> >  }
> >  
> > +/*
> > + * This function computes an effective utilization for the given CPU, to be
> > + * used for frequency selection given the linear relation: f = u * f_max.
> > + *
> > + * The scheduler tracks the following metrics:
> > + *
> > + *   cpu_util_{cfs,rt,dl,irq}()
> > + *   cpu_bw_dl()
> > + *
> > + * Where the cfs,rt and dl util numbers are tracked with the same metric and
> > + * synchronized windows and are thus directly comparable.
> > + *
> > + * The cfs,rt,dl utilization are the running times measured with rq->clock_task
> > + * which excludes things like IRQ and steal-time. These latter are then accrued
> > + * in the irq utilization.
> > + *
> > + * The DL bandwidth number otoh is not a measured metric but a value computed
> > + * based on the task model parameters and gives the minimal utilization
> > + * required to meet deadlines.
> > + */
> > +unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
> > +				 unsigned long max, enum cpu_util_type type,
> > +				 struct task_struct *p)
> > +{
> 	...
> > +}
> > +
> > +unsigned long sched_cpu_util(int cpu, enum cpu_util_type type,
> > +			     unsigned long max)
> > +{
> > +	return effective_cpu_util(cpu, cpu_util_cfs(cpu_rq(cpu)), max, type,
> > +				  NULL);
> > +}
> 
> Shouldn't all that be: #ifdef CONFIG_SMP ?

I didn't realize that these matrices are only available in case of SMP
and that's why schedutil isn't available for !SMP. I wonder what we
should be doing in cpufreq_cooling now ? Make it depend on SMP ? Or
calculate load the traditional way (the stuff I just removed) for !SMP
case ?

:)

-- 
viresh