linux-kernel - Re: [Patch v5 4/6] sched/fair: update cpu

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Date:   Tue, 19 Nov 2019 16:21:49 +0530
From:   Amit Kucheria <amit.kucheria@...durent.com>
To:     Thara Gopinath <thara.gopinath@...aro.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>, ionela.voinescu@....com,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Eduardo Valentin <edubezval@...il.com>, qperret@...gle.com,
        LKML <linux-kernel@...r.kernel.org>,
        Amit Daniel Kachhap <amit.kachhap@...il.com>,
        Javi Merino <javi.merino@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [Patch v5 4/6] sched/fair: update cpu_capcity to reflect thermal pressure

On Wed, Nov 6, 2019 at 12:20 AM Thara Gopinath
<thara.gopinath@...aro.org> wrote:
>
> cpu_capacity relflects the maximum available capacity of a cpu. Thermal

s/relflects/reflects

> 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.
>
> Other signals that are deducted from cpu_capacity to reflect the actual
> capacity available are rt and dl util_avg. util_avg tracks a binary signal
> and uses the weights 1024 and 0. Whereas thermal pressure is tracked
> using load_avg. load_avg uses the actual "delta" capacity as the weight.

Consider rephrasing as,

Currently, effective cpu capacity is calculated by deducting RT and DL
average utilization (util_avg) from cpu_capacity. For thermal
pressure, we use load_avg instead of util_avg which is a binary signal
(0 or 1024) because <put why here>


> 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 9fb0494..5f6c371 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -7738,6 +7738,7 @@ 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);
>
>         if (unlikely(used >= max))
>                 return 1;
> --
> 2.1.4
>