linux-kernel - Re: [RFC][PATCH 4/6] sched: Fold sched_class::switch{ing,ed}

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Message-ID: <20241030211506.GR14555@noisy.programming.kicks-ass.net>
Date: Wed, 30 Oct 2024 22:15:06 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Tejun Heo <tj@...nel.org>
Cc: mingo@...nel.org, juri.lelli@...hat.com, vincent.guittot@...aro.org,
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
	mgorman@...e.de, vschneid@...hat.com, void@...ifault.com,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 4/6] sched: Fold
 sched_class::switch{ing,ed}_{to,from}() into the change pattern

On Wed, Oct 30, 2024 at 11:12:32AM -1000, Tejun Heo wrote:
> On Wed, Oct 30, 2024 at 04:12:59PM +0100, Peter Zijlstra wrote:
> > --- a/kernel/sched/ext.c
> > +++ b/kernel/sched/ext.c
> > @@ -5199,20 +5204,24 @@ static int scx_ops_enable(struct sched_e
> >  	percpu_down_write(&scx_fork_rwsem);
> >  	scx_task_iter_start(&sti);
> >  	while ((p = scx_task_iter_next_locked(&sti))) {
> > +		unsigned int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE;
> >  		const struct sched_class *old_class = p->sched_class;
> >  		const struct sched_class *new_class =
> >  			__setscheduler_class(p->policy, p->prio);
> >  
> > +		if (old_class != new_class)
> > +			queue_flags |= DEQUEUE_CLASS;
> > +
> >  		if (old_class != new_class && p->se.sched_delayed)
> >  			dequeue_task(task_rq(p), p, DEQUEUE_SLEEP | DEQUEUE_DELAYED);
> >  
> >  		scoped_guard (sched_change, p, DEQUEUE_SAVE | DEQUEUE_MOVE) {
>                                                ^
> 					       queue_flags
> 					       
> >  			p->scx.slice = SCX_SLICE_DFL;
> >  			p->sched_class = new_class;
> > -			check_class_changing(task_rq(p), p, old_class);
> >  		}
> >  
> > -		check_class_changed(task_rq(p), p, old_class, p->prio);
> > +		if (!(queue_flags & DEQUEUE_CLASS))
> > +			check_prio_changed(task_rq(p), p, p->prio);
> 
> Maybe prio_changed can be moved into scoped_guard?

It wasn't before -- do you have need for it to be inside?