linux-kernel - Re: [PATCH v5 08/10] cpufreq/schedutil: take into account interrupt

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Date:   Mon, 28 May 2018 12:41:27 +0200
From:   Juri Lelli <juri.lelli@...hat.com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     peterz@...radead.org, mingo@...nel.org,
        linux-kernel@...r.kernel.org, rjw@...ysocki.net,
        dietmar.eggemann@....com, Morten.Rasmussen@....com,
        viresh.kumar@...aro.org, valentin.schneider@....com,
        quentin.perret@....com
Subject: Re: [PATCH v5 08/10] cpufreq/schedutil: take into account interrupt

Hi Vincent,

On 25/05/18 15:12, Vincent Guittot wrote:
> The time spent under interrupt can be significant but it is not reflected
> in the utilization of CPU when deciding to choose an OPP. Now that we have
> access to this metric, schedutil can take it into account when selecting
> the OPP for a CPU.
> The CPU utilization is :
>   irq util_avg + (1 - irq util_avg / max capacity ) * /Sum rq util_avg

IIUC the code below you actually propose that

 util = [(max_cap - util_irq) * util_rq] / max_cap + util_irq

where

 util_rq  = /Sum rq util_avg
 util_irq = irq util_avg

So, which one is what you have in mind? Or am I wrong? :)

[...]

>  static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu)
> @@ -190,9 +192,17 @@ static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu)
>  	if (rq->rt.rt_nr_running) {
>  		util = sg_cpu->max;
>  	} else {
> +		/* Sum rq utilization*/
>  		util = sg_cpu->util_dl;
>  		util += sg_cpu->util_cfs;
>  		util += sg_cpu->util_rt;
> +
> +		/* Weight rq's utilization to the normal context */
> +		util *= (sg_cpu->max - sg_cpu->util_irq);
> +		util /= sg_cpu->max;
> +
> +		/* Add interrupt utilization */
> +		util += sg_cpu->util_irq;

Thanks,

- Juri