linux-kernel - Re: [RFC][PATCH 2/3] sched: Add support to pick functions to take rf

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Message-ID: <20251008135830.GW4067720@noisy.programming.kicks-ass.net>
Date: Wed, 8 Oct 2025 15:58:30 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Vincent Guittot <vincent.guittot@...aro.org>
Cc: tj@...nel.org, linux-kernel@...r.kernel.org, mingo@...nel.org,
	juri.lelli@...hat.com, dietmar.eggemann@....com,
	rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
	vschneid@...hat.com, longman@...hat.com, hannes@...xchg.org,
	mkoutny@...e.com, void@...ifault.com, arighi@...dia.com,
	changwoo@...lia.com, cgroups@...r.kernel.org,
	sched-ext@...ts.linux.dev, liuwenfang@...or.com, tglx@...utronix.de,
	Joel Fernandes <joelagnelf@...dia.com>
Subject: Re: [RFC][PATCH 2/3] sched: Add support to pick functions to take rf

On Wed, Oct 08, 2025 at 03:16:58PM +0200, Vincent Guittot wrote:

> > +static struct task_struct *
> > +fair_server_pick_task(struct sched_dl_entity *dl_se, struct rq_flags *rf)
> >  {
> > -       return pick_next_task_fair(rq, prev, NULL);
> 
> The special case of a NULL rf pointer is used to skip
> sched_balance_newidle() at the end of pick_next_task_fair() in the
> pick_next_task() slo path when prev_balance has already it. This means
> that it will be called twice if prev is not a fair task.

Oh right. I suppose we can simply remove balance_fair.

> While reviewing this series, I also noticed an older issue that we
> have with check pelt lost idle time [1]
> [1] https://lore.kernel.org/all/20251008131214.3759798-1-vincent.guittot@linaro.org/

Let me go have a look.