linux-kernel - Re: [RFC][PATCH 0/3] sched: User Managed Concurrency Groups

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Message-ID: <CAFTs51XRJj1pwF6q5hwdGP0jtXmY81QQmTzyuA26fHMH0zCymw@mail.gmail.com>
Date:   Tue, 14 Dec 2021 19:46:25 -0800
From:   Peter Oskolkov <posk@...k.io>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>, juri.lelli@...hat.com,
        Vincent Guittot <vincent.guittot@...aro.org>,
        dietmar.eggemann@....com, Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, mgorman@...e.de,
        bristot@...hat.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        linux-api@...r.kernel.org, x86@...nel.org,
        Paul Turner <pjt@...gle.com>, Peter Oskolkov <posk@...gle.com>,
        Andrei Vagin <avagin@...gle.com>, Jann Horn <jannh@...gle.com>,
        Thierry Delisle <tdelisle@...terloo.ca>
Subject: Re: [RFC][PATCH 0/3] sched: User Managed Concurrency Groups

On Tue, Dec 14, 2021 at 12:55 PM Peter Zijlstra <peterz@...radead.org> wrote:
>
> Hi,
>
> This is actually tested code; but still missing the SMP wake-to-idle machinery.
> I still need to think about that.

Thanks, Peter!

At a first glance, your main patch does not look much smaller than
mine, and I thought the whole point of re-doing it was to throw away
extra features and make things smaller/simpler...

Anyway, I'll test your patchset over the next week or so and let you
know if anything really needed is missing (other than waking an idle
server if there is one on a worker wakeup; this piece is definitely
needed).

>
> I'll post my test-hack as a reply, but basically it does co-operative and
> preemptive UP-like user scheduling.
>
> Patches go on top of tip/master as they rely on the .fixup removal
> recently merged in tip/x86/core.
>
> Also, I still need to audit a bunch of mm code, because I'm not sure things are
> actually as well behaved as this code supposes they are.
>