From: Daniel Bristot de Oliveira <bristot@redhat.com>
To: Dietmar Eggemann <dietmar.eggemann@arm.com>,
Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>
Cc: linux-kernel@vger.kernel.org,
Vincent Guittot <vincent.guittot@linaro.org>,
Steven Rostedt <rostedt@goodmis.org>,
Quentin Perret <qperret@google.com>,
Valentin Schneider <valentin.schneider@arm.com>
Subject: Re: [PATCH] sched/deadline: Reduce rq lock contention in dl_add_task_root_domain()
Date: Wed, 20 Jan 2021 08:52:25 +0100 [thread overview]
Message-ID: <eae452b8-ea5c-8787-8292-e3d7d5f7a1f4@redhat.com> (raw)
In-Reply-To: <20210119083542.19856-1-dietmar.eggemann@arm.com>
On 1/19/21 9:35 AM, Dietmar Eggemann wrote:
> dl_add_task_root_domain() is called during sched domain rebuild:
>
> rebuild_sched_domains_locked()
> partition_and_rebuild_sched_domains()
> rebuild_root_domains()
> for all top_cpuset descendants:
> update_tasks_root_domain()
> for all tasks of cpuset:
> dl_add_task_root_domain()
>
> Change it so that only the task pi lock is taken to check if the task
> has a SCHED_DEADLINE (DL) policy. In case that p is a DL task take the
> rq lock as well to be able to safely de-reference root domain's DL
> bandwidth structure.
>
> Most of the tasks will have another policy (namely SCHED_NORMAL) and
> can now bail without taking the rq lock.
>
> One thing to note here: Even in case that there aren't any DL user
> tasks, a slow frequency switching system with cpufreq gov schedutil has
> a DL task (sugov) per frequency domain running which participates in DL
> bandwidth management.
>
> Reviewed-by: Quentin Perret <qperret@google.com>
> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Thanks!
-- Daniel
next prev parent reply other threads:[~2021-01-20 7:54 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-19 8:35 [PATCH] sched/deadline: Reduce rq lock contention in dl_add_task_root_domain() Dietmar Eggemann
2021-01-19 20:51 ` Valentin Schneider
2021-01-20 7:52 ` Daniel Bristot de Oliveira [this message]
2021-01-21 6:28 ` Juri Lelli
2021-02-08 13:43 ` Peter Zijlstra
2021-02-10 13:53 ` [tip: sched/core] " tip-bot2 for Dietmar Eggemann
2021-02-17 13:17 ` tip-bot2 for Dietmar Eggemann
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