linux-kernel - Re: [PATCH V3 3/3] thermal/cpu-cooling: Update thermal pressure in case of a maximum frequency capping

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Message-ID: <20190418094833.owlobrx6x5gclvhy@queper01-lin>
Date:   Thu, 18 Apr 2019 10:48:35 +0100
From:   Quentin Perret <quentin.perret@....com>
To:     Thara Gopinath <thara.gopinath@...aro.org>
Cc:     mingo@...hat.com, peterz@...radead.org, rui.zhang@...el.com,
        linux-kernel@...r.kernel.org, amit.kachhap@...il.com,
        viresh.kumar@...aro.org, javi.merino@...nel.org,
        edubezval@...il.com, daniel.lezcano@...aro.org,
        vincent.guittot@...aro.org, nicolas.dechesne@...aro.org,
        bjorn.andersson@...aro.org, dietmar.eggemann@....com
Subject: Re: [PATCH V3 3/3] thermal/cpu-cooling: Update thermal pressure in
 case of a maximum frequency capping

On Tuesday 16 Apr 2019 at 15:38:41 (-0400), Thara Gopinath wrote:
> diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
> @@ -177,6 +178,9 @@ static int cpufreq_thermal_notifier(struct notifier_block *nb,
>  
>  		if (policy->max > clipped_freq)
>  			cpufreq_verify_within_limits(policy, 0, clipped_freq);
> +
> +		sched_update_thermal_pressure(policy->cpus,
> +				policy->max, policy->cpuinfo.max_freq);

Is this something we could do this CPUFreq ? Directly in
cpufreq_verify_within_limits() perhaps ?

That would re-define the 'thermal pressure' framework in a more abstract
way and make the scheduler look at 'frequency capping' events,
regardless of the reason for capping.

That would reflect user-defined frequency constraint into cpu_capacity,
in addition to the thermal stuff. I'm not sure if there is another use
case for frequency capping ?

Perhaps the Intel boost stuff could be factored in there ? That is,
at times when the boost freq is not reachable capacity_of() would appear
smaller ... Unless this wants to be reflected instantaneously ?

Thoughts ?
Quentin