linux-kernel - Re: [PATCH v3 2/3] sched/fair: Take thermal pressure into account while estimating energy

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Message-ID: <2fa70564-e02a-06d5-2742-24dedccddea2@arm.com>
Date:   Mon, 14 Jun 2021 19:22:01 +0100
From:   Lukasz Luba <lukasz.luba@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     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>,
        Dietmar Eggemann <dietmar.eggemann@....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>, amitk@...nel.org,
        Zhang Rui <rui.zhang@...el.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH v3 2/3] sched/fair: Take thermal pressure into account
 while estimating energy



On 6/14/21 5:03 PM, Vincent Guittot wrote:
> On Thu, 10 Jun 2021 at 17:03, Lukasz Luba <lukasz.luba@....com> wrote:

[snip]

>> In the existing code the raw value of arch_scale_cpu_capacity() is used
>> for clamping the returned CPU utilization from effective_cpu_util().
>> This patch fixes issue with too big single CPU utilization, by introducing
>> clamping to the allowed CPU capacity. The allowed CPU capacity is a CPU
>> capacity reduced by thermal pressure signal. We rely on this load avg
> 
> you don't rely on load avg value but on raw thermal pressure value now

Good catch, I'll change that description.

> 
>> geometric series in similar way as other mechanisms in the scheduler.
>>

[snip]

>>
>> +       thermal_pressure = arch_scale_thermal_pressure(cpumask_first(pd_mask));
> 
> Do you really need to use this intermediate variable thermal_pressure
> ? Seems to be used only below

True, it's used only here. I'll remove this variable in the v4.

> 
> With these 2 comments above fixed,
> 
> Reviewed-by: Vincent Guittot <vincent.guittot@...aro.org>

Thank you for the review!

Regards,
Lukasz