From: Peter Zijlstra <peterz@infradead.org>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: mingo@redhat.com, juri.lelli@redhat.com,
dietmar.eggemann@arm.com, rostedt@goodmis.org,
bsegall@google.com, mgorman@suse.de, vschneid@redhat.com,
kprateek.nayak@amd.com, linux-kernel@vger.kernel.org,
qyousef@layalina.io
Subject: Re: [PATCH] sched/eevdf: Delayed dequeue task can't preempt
Date: Thu, 2 Jul 2026 09:43:04 +0200 [thread overview]
Message-ID: <20260702074304.GC49951@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20260701164920.1571352-1-vincent.guittot@linaro.org>
On Wed, Jul 01, 2026 at 06:49:20PM +0200, Vincent Guittot wrote:
> Load balancing can migrate delayed dequeue tasks to even the load between
> CPUs.
>
> sched_balance_rq()
> -> detach_task()
> -> deactivate_task(DEQUEUE_NOCLOCK)
> -> set_task_cpu(dst_cpu)
>
> -> attach_task()
> -> activate_task(ENQUEUE_NOCLOCK)
> -> wakeup_preempt()
>
> A delayed task with shorter slice can be dequeued during pick_next_entity()
> but then jump to preempt because eligible.
Cute.
Perhaps we can look at enqueue()'s place entity and determine
eligibility there and complete the delayed dequeue there. But that's
definitely something for after the holidays I suppose.
I'll go stick it in tip/sched/core.
next prev parent reply other threads:[~2026-07-02 7:43 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-01 16:49 [PATCH] sched/eevdf: Delayed dequeue task can't preempt Vincent Guittot
2026-07-02 4:56 ` K Prateek Nayak
2026-07-02 7:51 ` Vincent Guittot
2026-07-02 7:43 ` Peter Zijlstra [this message]
2026-07-02 7:53 ` Vincent Guittot
2026-07-02 9:01 ` Peter Zijlstra
2026-07-02 9:07 ` Vincent Guittot
2026-07-02 7:47 ` [tip: sched/core] " tip-bot2 for Vincent Guittot
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