linux-kernel - Re: [PATCH 10/24] sched/uclamg: Handle delayed dequeue

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Message-ID: <20240905141857.GO4723@noisy.programming.kicks-ass.net>
Date: Thu, 5 Sep 2024 16:18:57 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Dietmar Eggemann <dietmar.eggemann@....com>
Cc: Hongyan Xia <hongyan.xia2@....com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Luis Machado <luis.machado@....com>, mingo@...hat.com,
	juri.lelli@...hat.com, rostedt@...dmis.org, bsegall@...gle.com,
	mgorman@...e.de, vschneid@...hat.com, linux-kernel@...r.kernel.org,
	kprateek.nayak@....com, wuyun.abel@...edance.com,
	youssefesmat@...omium.org, tglx@...utronix.de, efault@....de
Subject: Re: [PATCH 10/24] sched/uclamg: Handle delayed dequeue

On Thu, Sep 05, 2024 at 03:02:44PM +0200, Dietmar Eggemann wrote:

> From 0d7e8d057f49a47e0f3f484ac7d41e047dccec38 Mon Sep 17 00:00:00 2001
> From: Dietmar Eggemann <dietmar.eggemann@....com>
> Date: Thu, 5 Sep 2024 00:05:23 +0200
> Subject: [PATCH] kernel/sched: Fix util_est accounting for DELAY_DEQUEUE
> 
> Remove delayed tasks from util_est even they are runnable.
> 
> Exclude delayed task which are (a) migrating between rq's or (b) in a
> SAVE/RESTORE dequeue/enqueue.
> 
> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@....com>
> ---
>  kernel/sched/fair.c | 16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 1e693ca8ebd6..5c32cc26d6c2 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6948,18 +6948,19 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
>  	int rq_h_nr_running = rq->cfs.h_nr_running;
>  	u64 slice = 0;
>  
> -	if (flags & ENQUEUE_DELAYED) {
> -		requeue_delayed_entity(se);
> -		return;
> -	}
> -
>  	/*
>  	 * The code below (indirectly) updates schedutil which looks at
>  	 * the cfs_rq utilization to select a frequency.
>  	 * Let's add the task's estimated utilization to the cfs_rq's
>  	 * estimated utilization, before we update schedutil.
>  	 */
> -	util_est_enqueue(&rq->cfs, p);
> +	if (!(p->se.sched_delayed && (task_on_rq_migrating(p) || (flags & ENQUEUE_RESTORE))))
> +		util_est_enqueue(&rq->cfs, p);
> +
> +	if (flags & ENQUEUE_DELAYED) {
> +		requeue_delayed_entity(se);
> +		return;
> +	}
>  
>  	/*
>  	 * If in_iowait is set, the code below may not trigger any cpufreq
> @@ -7177,7 +7178,8 @@ static int dequeue_entities(struct rq *rq, struct sched_entity *se, int flags)
>   */
>  static bool dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
>  {
> -	util_est_dequeue(&rq->cfs, p);
> +	if (!(p->se.sched_delayed && (task_on_rq_migrating(p) || (flags & DEQUEUE_SAVE))))
> +		util_est_dequeue(&rq->cfs, p);
>  
>  	if (dequeue_entities(rq, &p->se, flags) < 0) {
>  		if (!rq->cfs.h_nr_running)

Thanks!