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

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Message-ID: <20191106165646.vc7j4hbhj2hcrku4@e107158-lin.cambridge.arm.com>
Date:   Wed, 6 Nov 2019 16:56:48 +0000
From:   Qais Yousef <qais.yousef@....com>
To:     Thara Gopinath <thara.gopinath@...aro.org>
Cc:     mingo@...hat.com, peterz@...radead.org, 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 v5 4/6] sched/fair: update cpu_capcity to reflect thermal
 pressure

On 11/05/19 13:49, 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.
> 
> 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.

I think you intended to put this as comment...

> 
> 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);

... here?

I find the explanation hard to parse too. Do you think you can rephrase it?
Something based on what you wrote here would be more understandable IMHO:
https://lore.kernel.org/lkml/5DBB05BC.40502@linaro.org/


Thanks!

--
Qais Yousef

>  
>  	if (unlikely(used >= max))
>  		return 1;
> -- 
> 2.1.4
>