From: David Vernet <void@manifault.com>
To: Tejun Heo <tj@kernel.org>
Cc: peterz@infradead.org, mingo@redhat.com, kernel-team@meta.com,
linux-kernel@vger.kernel.org, sched-ext@meta.com
Subject: Re: [PATCH 2/3] sched/core: Add ENQUEUE_RQ_SELECTED to indicate whether ->select_task_rq() was called
Date: Fri, 27 Sep 2024 19:38:55 -0500 [thread overview]
Message-ID: <20240928003855.GB2717@maniforge> (raw)
In-Reply-To: <20240927234838.152112-3-tj@kernel.org>
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On Fri, Sep 27, 2024 at 01:46:12PM -1000, Tejun Heo wrote:
> During ttwu, ->select_task_rq() can be skipped if only one CPU is allowed or
> migration is disabled. sched_ext schedulers may perform operations such as
> direct dispatch from ->select_task_rq() path and it is useful for them to
> know whether ->select_task_rq() was skipped in the ->enqueue_task() path.
>
> Currently, sched_ext schedulers are using ENQUEUE_WAKEUP for this purpose
> and end up assuming incorrectly that ->select_task_rq() was called for tasks
> that are bound to a single CPU or migration disabled.
>
> Make select_task_rq() indicate whether ->select_task_rq() was called by
> setting WF_RQ_SELECTED in *wake_flags and make ttwu_do_activate() map that
> to ENQUEUE_RQ_SELECTED for ->enqueue_task().
>
> This will be used by sched_ext to fix ->select_task_rq() skip detection.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: David Vernet <void@manifault.com>
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next prev parent reply other threads:[~2024-09-28 0:38 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-27 23:46 [PATCHSET sched/urgent, sched_ext/for-6.12-fixes] sched/core, sched_ext: Add ENQUEUE_RQ_SELECTED to fix ->select_task_rq() skip detection in sched_ext schedulers Tejun Heo
2024-09-27 23:46 ` [PATCH 1/3] sched/core: Make select_task_rq() take the pointer to wake_flags instead of value Tejun Heo
2024-09-28 0:38 ` David Vernet
2024-09-27 23:46 ` [PATCH 2/3] sched/core: Add ENQUEUE_RQ_SELECTED to indicate whether ->select_task_rq() was called Tejun Heo
2024-09-28 0:38 ` David Vernet [this message]
2024-10-01 20:12 ` Tejun Heo
2024-10-04 20:14 ` Tejun Heo
2024-10-05 9:38 ` Peter Zijlstra
2024-10-07 16:44 ` Tejun Heo
2024-09-27 23:46 ` [PATCH 3/3] sched_ext, scx_qmap: Add and use SCX_ENQ_CPU_SELECTED Tejun Heo
2024-09-28 0:39 ` David Vernet
2024-09-28 13:21 ` Andrea Righi
2024-09-28 16:52 ` Tejun Heo
2024-10-07 20:20 ` [PATCHSET sched/urgent, sched_ext/for-6.12-fixes] sched/core, sched_ext: Add ENQUEUE_RQ_SELECTED to fix ->select_task_rq() skip detection in sched_ext schedulers Tejun Heo
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