linux-kernel - Re: [PATCH v6 10/14] sched/cpufreq: Refactor the utilization aggregation method

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Message-ID: <20180910100719.uan6gskxpgu25dj5@queper01-lin>
Date:   Mon, 10 Sep 2018 11:07:21 +0100
From:   Quentin Perret <quentin.perret@....com>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     peterz@...radead.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, gregkh@...uxfoundation.org,
        mingo@...hat.com, dietmar.eggemann@....com,
        morten.rasmussen@....com, chris.redpath@....com,
        patrick.bellasi@....com, valentin.schneider@....com,
        vincent.guittot@...aro.org, thara.gopinath@...aro.org,
        viresh.kumar@...aro.org, tkjos@...gle.com, joel@...lfernandes.org,
        smuckle@...gle.com, adharmap@...eaurora.org,
        skannan@...eaurora.org, pkondeti@...eaurora.org,
        juri.lelli@...hat.com, edubezval@...il.com,
        srinivas.pandruvada@...ux.intel.com, currojerez@...eup.net,
        javi.merino@...nel.org
Subject: Re: [PATCH v6 10/14] sched/cpufreq: Refactor the utilization
 aggregation method

On Monday 10 Sep 2018 at 11:53:58 (+0200), Rafael J. Wysocki wrote:
> On Monday, August 20, 2018 11:44:16 AM CEST Quentin Perret wrote:
> > Schedutil aggregates the PELT signals of CFS, RT, DL and IRQ in order
> > to decide which frequency to request. Energy Aware Scheduling (EAS)
> > needs to be able to predict those requests to assess the energy impact
> > of scheduling decisions. However, the PELT signals aggregation is only
> > done in schedutil for now, hence making it hard to synchronize it with
> > EAS.
> > 
> > To address this issue, introduce schedutil_freq_util() to perform the
> > aforementioned aggregation and make it available to other parts of the
> > scheduler. Since frequency selection and energy estimation still need
> > to deal with RT and DL signals slightly differently, schedutil_freq_util()
> > is called with a different 'type' parameter in those two contexts, and
> > returns an aggregated utilization signal accordingly.
> 
> This is complementary to patch [02/14] IMO.
> 
> schedutil_freq_util() and map_util_freq() introduced by that patch should
> always be used together as they are two parts of one algorithm in my view.

I agree.

> Would it be possible to make that clearer?

I could squash the two at the beginning of the series in a preparatory
patch that refactors schedutil for EAS all in one go, with a clear
mention of what we intend to do (make EAS depend on sugov) in the commit
message.

Would that work ?

Thanks,
Quentin