Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 18 Apr 2019 10:48:35 +0100
From:   Quentin Perret <quentin.perret@arm.com>
To:     Thara Gopinath <thara.gopinath@linaro.org>
Cc:     mingo@redhat.com, peterz@infradead.org, rui.zhang@intel.com,
        linux-kernel@vger.kernel.org, amit.kachhap@gmail.com,
        viresh.kumar@linaro.org, javi.merino@kernel.org,
        edubezval@gmail.com, daniel.lezcano@linaro.org,
        vincent.guittot@linaro.org, nicolas.dechesne@linaro.org,
        bjorn.andersson@linaro.org, dietmar.eggemann@arm.com
Subject: Re: [PATCH V3 3/3] thermal/cpu-cooling: Update thermal pressure in
 case of a maximum frequency capping
Message-ID: <20190418094833.owlobrx6x5gclvhy@queper01-lin>
References: <1555443521-579-1-git-send-email-thara.gopinath@linaro.org>
 <1555443521-579-4-git-send-email-thara.gopinath@linaro.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1555443521-579-4-git-send-email-thara.gopinath@linaro.org>
User-Agent: NeoMutt/20171215
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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