linux-kernel - Re: [Patch v4 4/6] sched/fair: update cpu

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Message-ID: <20191028153010.GE4097@hirez.programming.kicks-ass.net>
Date:   Mon, 28 Oct 2019 16:30:10 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Qais Yousef <qais.yousef@....com>
Cc:     Thara Gopinath <thara.gopinath@...aro.org>, mingo@...hat.com,
        ionela.voinescu@....com, vincent.guittot@...aro.org,
        rui.zhang@...el.com, edubezval@...il.com, qperret@...gle.com,
        linux-kernel@...r.kernel.org, amit.kachhap@...il.com,
        javi.merino@...nel.org, daniel.lezcano@...aro.org
Subject: Re: [Patch v4 4/6] sched/fair: update cpu_capcity to reflect thermal
 pressure

On Wed, Oct 23, 2019 at 01:28:40PM +0100, Qais Yousef wrote:
> On 10/22/19 16:34, Thara Gopinath wrote:
> > cpu_capacity relflects the maximum available capacity of a cpu. Thermal
> > pressure on a cpu means this maximum available capacity is reduced. This
> > patch reduces the average thermal pressure for a cpu from its maximum
> > available capacity so that cpu_capacity reflects the actual
> > available capacity.
> > 
> > Signed-off-by: Thara Gopinath <thara.gopinath@...aro.org>
> > ---
> >  kernel/sched/fair.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 4f9c2cb..be3e802 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -7727,6 +7727,7 @@ static unsigned long scale_rt_capacity(struct sched_domain *sd, int cpu)
> >  
> >  	used = READ_ONCE(rq->avg_rt.util_avg);
> >  	used += READ_ONCE(rq->avg_dl.util_avg);
> > +	used += READ_ONCE(rq->avg_thermal.load_avg);
> 
> Maybe a naive question - but can we add util_avg with load_avg without
> a conversion? I thought the 2 signals have different properties.

Changelog of patch #1 explains, it's in that dense blob of text.

But yes, you're quite right that that wants a comment here.