linux-kernel - Re: [RFC PATCH v3 2/3] docs: scheduler: Add scheduler overview documentation

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Message-ID: <CAJz2qXkrcobNC0Oh94p1e5chMdgzm6X1VCU9Es-1_=Zm5V0HMg@mail.gmail.com>
Date:   Wed, 13 May 2020 16:38:55 +0300
From:   John Mathew <john.mathew@...kie.com>
To:     Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     Valentin Schneider <valentin.schneider@....com>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        corbet@....net, mingo@...hat.com, peterz@...radead.org,
        juri.lelli@...hat.com,
        Vincent Guittot <vincent.guittot@...aro.org>,
        rostedt@...dmis.org, Benjamin Segall <bsegall@...gle.com>,
        mgorman@...e.de, bristot@...hat.com, tsbogend@...ha.franken.de,
        Lukas Bulwahn <lukas.bulwahn@...il.com>, x86@...nel.org,
        linux-mips@...r.kernel.org, tglx@...utronix.de,
        Mostafa Chamanara <mostafa.chamanara@...emark.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Oleg Tsymbal <oleg.tsymbal@...kie.com>
Subject: Re: [RFC PATCH v3 2/3] docs: scheduler: Add scheduler overview documentation

On Fri, May 8, 2020 at 1:58 PM Dietmar Eggemann
<dietmar.eggemann@....com> wrote:
>
> On 07/05/2020 23:15, Valentin Schneider wrote:
> >
> > On 07/05/20 19:05, John Mathew wrote:
>
> [...]
>
> > It would also be an opportunity to have one place to (at least briefly)
> > describe what the different sched classes do wrt capacity asymmetry - CFS
> > does one thing, RT now does one thing (see Qais' work), and DL will
> > hopefully soon follow (see Dietmar's work).
> >
> > I'd be happy to contribute (some of) that, if it can be deemed useful (I
> > personally think it might).
>
> I like the idea.
>
> Essentially all the code which is guarded by the 'if
> (static_branch_unlikely(&sched_asym_cpucapacity)' condition or which
> sets it during bring-up.
>
> * 'Cpu capacity < SCHED_LOAD_SCALE for non-big' CPUs setting during
>    bringup (necessary dt binding, CPUfreq influence)
>
> * CFS capacity awareness:
>
>   * wakeup - select_idle_capacity() (replaced wake_cap() & slow path to
>              cover DynamIQ and classical big.LITTLE)
>
>   * load_balance - misfit handling
>
> * RT & DL capacity awareness
>
> * ... & the relation to EAS (Documentation/scheduler/sched-energy.rst)
>
> This is what we referred to (at least internally) as CAS (Capacity-Aware
> Scheduling).

Added in pathset v4.

Thanks