Re: [PATCH 4/6 v2] sched/eevdf: Cancel slice protection if short slice task is eligible

[K Prateek Nayak]

Hello Vincent,

On 6/15/2026 9:54 PM, Vincent Guittot wrote:
> @@ -9897,16 +9892,23 @@ static void wakeup_preempt_fair(struct rq *rq, struct task_struct *p, int wake_f
>  	if (!nse && cfs_rq->nr_queued)
>  		goto pick;
>  
> +	/*
> +	 * If @p is eligible but not the next task to run then cancel protection
> +	 * to prevent large scheduling latency
> +	 */
> +	if (preempt_action == PREEMPT_WAKEUP_SHORT && entity_eligible(cfs_rq, pse))
> +		goto preempt;

Can't we do this independent of the "pick" path if we are going to
resched anyways?

I suppose it is for set_next_buddy() bits but, if nse == pse, we cancel
the slice protection and resched anyways and the pick will naturally
go to pse so does set_next_buddy() even matter?

Instead, can PREEMPT_WAKEUP_SHORT path just do a set_preempt_buddy()
beforehand to ensure the task with the smallest deadline is already
the ->next and pick_next_entity() readily returns that?

> +
>  	if (sched_feat(RUN_TO_PARITY))
>  		update_protect_slice(cfs_rq, se);
>  
>  	return;
>  
>  preempt:
> -	if (preempt_action == PREEMPT_WAKEUP_SHORT) {
> -		cancel_protect_slice(se);
> +	cancel_protect_slice(se);
> +
> +	if (preempt_action == PREEMPT_WAKEUP_SHORT && nse == pse)
>  		set_next_buddy(&p->se);
> -	}
>  
>  	resched_curr_lazy(rq);
>  }

-- 
Thanks and Regards,
Prateek