linux-kernel - Re: [PATCH v2] sched_ext: Trigger ops.update_idle() from pick_task

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Message-ID: <Zw377f2g1JnIYNSu@gpd3>
Date: Tue, 15 Oct 2024 07:21:49 +0200
From: Andrea Righi <andrea.righi@...ux.dev>
To: Tejun Heo <tj@...nel.org>
Cc: David Vernet <void@...ifault.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>,
	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>,
	Valentin Schneider <vschneid@...hat.com>,
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH v2] sched_ext: Trigger ops.update_idle() from
 pick_task_idle()

On Mon, Oct 14, 2024 at 03:12:16PM -1000, Tejun Heo wrote:
> Hello,
> 
> On Tue, Oct 15, 2024 at 12:06:03AM +0200, Andrea Righi wrote:
> > @@ -459,13 +459,13 @@ static void put_prev_task_idle(struct rq *rq, struct task_struct *prev, struct t
> >  static void set_next_task_idle(struct rq *rq, struct task_struct *next, bool first)
> >  {
> >  	update_idle_core(rq);
> > -	scx_update_idle(rq, true);
> >  	schedstat_inc(rq->sched_goidle);
> >  	next->se.exec_start = rq_clock_task(rq);
> >  }
> >  
> >  struct task_struct *pick_task_idle(struct rq *rq)
> >  {
> > +	scx_update_idle(rq, true);
> 
> Thanks a lot for debugging this. Both the analysis and solution make sense
> to me. However, as this puts scx_update_idle() in a different place from
> other idle handling functions, can you please add a comment explaining why
> it needs to be in pick_task_idle() instead of set_next_task_idle()?
> 
> Thanks.

Sure, I'll send a v3 with a proper comment.

Thanks,
-Andrea

> 
> -- 
> tejun