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

Peter Zijlstra
2024-09-05T14:19:12Z

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@arm.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@arm.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!