linux-kernel - Re: [PATCH v4 2/3] sched/fair: Take thermal pressure into account while estimating energy

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Message-ID: <79dbb2ad-88c1-ff08-59c8-7728d37ee78a@arm.com>
Date:   Wed, 16 Jun 2021 21:22:40 +0100
From:   Lukasz Luba <lukasz.luba@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Dietmar Eggemann <dietmar.eggemann@....com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "open list:THERMAL" <linux-pm@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Quentin Perret <qperret@...gle.com>,
        Vincent Donnefort <vincent.donnefort@....com>,
        Beata Michalska <Beata.Michalska@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>, segall@...gle.com,
        Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Thara Gopinath <thara.gopinath@...aro.org>,
        Amit Kachhap <amit.kachhap@...il.com>,
        Amit Kucheria <amitk@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH v4 2/3] sched/fair: Take thermal pressure into account
 while estimating energy



On 6/16/21 8:25 PM, Vincent Guittot wrote:
> On Wed, 16 Jun 2021 at 19:24, Dietmar Eggemann <dietmar.eggemann@....com> wrote:
>>
>> On 15/06/2021 18:09, Lukasz Luba wrote:
>>>
>>> On 6/15/21 4:31 PM, Dietmar Eggemann wrote:
>>>> On 14/06/2021 21:11, Lukasz Luba wrote:
>>
>> [...]
>>
>>>> It's important to highlight that this will only fix this issue between
>>>> schedutil and EAS when it's due to `thermal pressure` (today only via
>>>> CPU cooling). There are other places which could restrict policy->max
>>>> via freq_qos_update_request() and EAS will be unaware of it.
>>>
>>> True, but for this I have some other plans.
>>
>> As long as people are aware of the fact that this was developed to be
>> beneficial for `EAS - IPA` integration, I'm fine with this.
> 
> I don't think it's only for EAS - IPA. Thermal_pressure can be used by
> HW throttling like here:
> https://lkml.org/lkml/2021/6/8/1791
> 
> EAS is involved but not IPA

Thank you Vincent for pointing to Thara's patches. Indeed, this is a
good example. We will have to provide similar for our SCMI perf
notifications - these are the plans that I've mentioned. In both
new examples, the IPA (or other governors) won't be even involved.