linux-kernel - Re: [PATCH v23 5/9] sched: Add logic to zap balance callbacks if we pick again

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Message-ID: <986aca02-af4b-4453-87f8-0d75672301b2@amd.com>
Date: Fri, 31 Oct 2025 09:20:43 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: John Stultz <jstultz@...gle.com>
CC: LKML <linux-kernel@...r.kernel.org>, Joel Fernandes
	<joelagnelf@...dia.com>, Qais Yousef <qyousef@...alina.io>, Ingo Molnar
	<mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Juri Lelli
	<juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>, Valentin Schneider
	<vschneid@...hat.com>, Steven Rostedt <rostedt@...dmis.org>, Ben Segall
	<bsegall@...gle.com>, Zimuzo Ezeozue <zezeozue@...gle.com>, Mel Gorman
	<mgorman@...e.de>, Will Deacon <will@...nel.org>, Waiman Long
	<longman@...hat.com>, Boqun Feng <boqun.feng@...il.com>, "Paul E. McKenney"
	<paulmck@...nel.org>, Metin Kaya <Metin.Kaya@....com>, Xuewen Yan
	<xuewen.yan94@...il.com>, Thomas Gleixner <tglx@...utronix.de>, "Daniel
 Lezcano" <daniel.lezcano@...aro.org>, Suleiman Souhlal <suleiman@...gle.com>,
	kuyo chang <kuyo.chang@...iatek.com>, hupu <hupu.gm@...il.com>,
	<kernel-team@...roid.com>
Subject: Re: [PATCH v23 5/9] sched: Add logic to zap balance callbacks if we
 pick again

Hello John,

On 10/31/2025 8:45 AM, John Stultz wrote:
>>> -             if (next == rq->idle)
>>> +             }
>>> +             if (next == rq->idle) {
>>> +                     zap_balance_callbacks(rq);
>>
>> Also I would have preferred to have that zap_balance_callbacks() in
>> proxy_resched_idle() but this is okay too.
> 
> So my initial hesitation here is just we call proxy_resched_idle() in
> other situations where we might return NULL from find_proxy_task() as
> well. So this avoids calling zap_balance_callbacks() twice.
> 
> But thinking some more, later in the full series we often call
> proxy_resched_idle() in those paths where we are briefly dropping the
> rq lock and we often call zap_balance_callbacks as well there. I'll
> take a closer look at the full patch series and see if that doesn't
> make sense to consolidate then.  Not 100% sure it will work out, but
> worth looking into.

I don't have any strong feelings btw. What you have currently works
well. thank you for the additional background. I should go back and
take a look at the full tree again to get a full picture.

-- 
Thanks and Regards,
Prateek