linux-kernel - Re: [RFC PATCH 09/11] sched/rt: Fix proxy/current (push,pull)ability

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Message-ID: <xhsmho7u6wjy4.mognet@vschneid.remote.csb>
Date:   Thu, 20 Oct 2022 17:14:59 +0100
From:   Valentin Schneider <vschneid@...hat.com>
To:     Juri Lelli <juri.lelli@...hat.com>
Cc:     Connor O'Brien <connoro@...gle.com>, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com, John Stultz <jstultz@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Qais Yousef <qais.yousef@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: Re: [RFC PATCH 09/11] sched/rt: Fix proxy/current (push,pull)ability

On 20/10/22 15:30, Juri Lelli wrote:
> On 19/10/22 18:05, Valentin Schneider wrote:
>> One possible change here is to make the blocked chain migrate towards the
>> proxy rather than the owner - this makes scheduling priority considerations
>> a bit saner, but is bad towards the owner (migrating blocked tasks is
>> "cheap", migrating running tasks isn't).
>
> Plus we need to consider owner's affinity, maybe it can't really migrate
> towards proxy's CPU.
>

Right, "little" detail I forgot...

> It looks like in general we would like to perform load balancing
> decisions considering potential proxies attributes? Guess it might soon
> turn into a mess to implement, though.

I can't think of anything clever right now, but we do need something like
that to get "feature parity" with rtmutexes.