From: Peter Zijlstra <peterz@infradead.org>
To: Qais Yousef <qais.yousef@arm.com>
Cc: Xuewen Yan <xuewen.yan94@gmail.com>,
valentin.schneider@arm.com, mingo@redhat.com,
juri.lelli@redhat.com, vincent.guittot@linaro.org,
dietmar.eggemann@arm.com, rostedt@goodmis.org,
bsegall@google.com, mgorman@suse.de, bristot@redhat.com,
linux-kernel@vger.kernel.org, patrick.bellasi@matbug.net,
qperret@google.com
Subject: Re: [PATCH v2] sched/uclamp: Avoid getting unreasonable ucalmp value when rq is idle
Date: Fri, 2 Jul 2021 14:00:29 +0200 [thread overview]
Message-ID: <YN7/3RkISFqM4rt+@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20210702115421.gcju2vluhof6rp6f@e107158-lin.cambridge.arm.com>
On Fri, Jul 02, 2021 at 12:54:21PM +0100, Qais Yousef wrote:
> Yep. How about the below?
>
> --->8---
>
> sched/uclamp: Ignore max aggregation if rq is idle
>
> When a task wakes up on an idle rq, uclamp_rq_util_with() would max
> aggregate with rq value. But since there is no task enqueued yet, the
> values are stale based on the last task that was running. When the new
> task actually wakes up and enqueued, then the rq uclamp values should
> reflect that of the newly woken up task effective uclamp values.
>
> This is a problem particularly for uclamp_max because it default to
> 1024. If a task p with uclamp_max = 512 wakes up, then max aggregation
> would ignore the capping that should apply when this task is enqueued,
> which is wrong.
>
> Fix that by ignoring max aggregation if the rq is idle since in that
> case the effective uclamp value of the rq will be the ones of the task
> that will wake up.
>
> --->8---
Much better, I've updated it. Thanks!
next prev parent reply other threads:[~2021-07-02 12:00 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-30 14:12 [PATCH v2] sched/uclamp: Avoid getting unreasonable ucalmp value when rq is idle Xuewen Yan
2021-06-30 14:24 ` Valentin Schneider
2021-07-01 11:32 ` Qais Yousef
2021-07-02 11:12 ` Peter Zijlstra
2021-07-02 11:54 ` Qais Yousef
2021-07-02 12:00 ` Peter Zijlstra [this message]
2021-07-02 12:12 ` Valentin Schneider
2021-07-02 13:03 ` Xuewen Yan
2021-07-05 7:53 ` [tip: sched/urgent] sched/uclamp: Ignore max aggregation if " tip-bot2 for Xuewen Yan
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