linux-kernel - Re: [RFC 1/1] sched: Skip redundant operations for proxy tasks needing return migration

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Message-ID: <CANDhNCoLYSFfry3bKhdC+YC1JYhtcgDpGLHTt-5v_4yDtR9QQw@mail.gmail.com>
Date: Tue, 10 Jun 2025 22:05:02 -0700
From: John Stultz <jstultz@...gle.com>
To: hupu <hupu.gm@...il.com>
Cc: peterz@...radead.org, linux-kernel@...r.kernel.org, juri.lelli@...hat.com, 
	vschneid@...hat.com, mingo@...hat.com, vincent.guittot@...aro.org, 
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com, 
	mgorman@...e.de, hupu@...nssion.com, Suleiman Souhlal <suleiman@...gle.com>
Subject: Re: [RFC 1/1] sched: Skip redundant operations for proxy tasks
 needing return migration

On Tue, Jun 10, 2025 at 7:32 PM hupu <hupu.gm@...il.com> wrote:
>
> Hi John,
> It has been a few days without any response to this email. I'm
> resending it for further discussion.

Apologies, I'm swamped at the moment with some other items and haven't
had time to give your suggestions enough serious thought to reply. :(

I have made some slow progress on a few items. Suggested by Suleiman,
I've reworked the migration logic to be considered after the owner
on_rq check, so we avoid migrating tasks to only realize they are
waiting on a sleeping owner and pulling them off the rq. This should
help reduce the number of migrations we make.

Unfortunately I've also been tripping over a crash with the full
series (not the portion I'm currently submitting upstream) that often
takes 30+ hours to reproduce and extra debugging logic seems to make
it even harder to hit. With all the other tasks, keeping enough
context in my head to make progress on this has been frustratingly
slow.

I'll hopefully have something to share soon and I can

thanks
-john