Re: [PATCH] sched/uclamp: Let each sched_class handle uclamp

[Hongyan Xia]

On 05/03/2025 18:22, Dietmar Eggemann wrote:
> On 27/02/2025 14:54, Hongyan Xia wrote:
>
> [...]
>
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 857808da23d8..7e5a653811ad 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -6941,8 +6941,10 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
> >   	 * Let's add the task's estimated utilization to the cfs_rq's
> >   	 * estimated utilization, before we update schedutil.
> >   	 */
> > -	if (!(p->se.sched_delayed && (task_on_rq_migrating(p) || (flags & ENQUEUE_RESTORE))))
> > +	if (!(p->se.sched_delayed && (task_on_rq_migrating(p) || (flags & ENQUEUE_RESTORE)))) {
> > +		uclamp_rq_inc(rq, p);
> >   		util_est_enqueue(&rq->cfs, p);
> > +	}
>
> So you want to have p uclamp-enqueued so that its uclamp_min value
> counts for the cpufreq_update_util()/cfs_rq_util_change() calls later in
> enqueue_task_fair?
>
>    if (p->in_iowait)
>      cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT);
>
>    enqueue_entity() -> update_load_avg() -> cfs_rq_util_change() ->
>    cpufreq_update_util()
>
> But if you do this before requeue_delayed_entity() (1) you will not
> uclamp-enqueue p which got his ->sched_delayed just cleared in (1)?

Sorry I'm not sure I'm following. The only condition of the 
uclamp_rq_inc() here should be

    if (!(p->se.sched_delayed && (task_on_rq_migrating(p) || (flags & 
ENQUEUE_RESTORE))))

Could you elaborate why it doesn't get enqueued?