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Date:   Wed, 19 Apr 2023 07:18:51 +0200
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Subject: Re: [RFC PATCH v1] sched/uclamp: Introduce
 SCHED_FLAG_RESET_UCLAMP_ON_FORK flag
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To:     David Dai <davidai@google.com>, Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Valentin Schneider <vschneid@redhat.com>
Cc:     Qais Yousef <qyousef@google.com>,
        Quentin Perret <qperret@google.com>,
        Saravana Kannan <saravanak@google.com>,
        kernel-team@android.com, linux-kernel@vger.kernel.org
References: <20230416213406.2966521-1-davidai@google.com>
From:   Dietmar Eggemann <dietmar.eggemann@arm.com>
In-Reply-To: <20230416213406.2966521-1-davidai@google.com>
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On 16/04/2023 23:34, David Dai wrote:
> A userspace service may manage uclamp dynamically for individual tasks and
> a child task will unintentionally inherit a pesudo-random uclamp setting.
> This could result in the child task being stuck with a static uclamp value

Could you explain this with a little bit more detail? Why isn't the
child task also managed by the userspace service?

The child task will only make a difference if it's on the rq.

Does this issue happen with uclamp mainline or only with Android's
slightly different version (max- vs. sum aggregation)?

> that results in poor performance or poor power.
> 
> Using SCHED_FLAG_RESET_ON_FORK is too coarse for this usecase and will
> reset other useful scheduler attributes. Adding a
> SCHED_FLAG_RESET_UCLAMP_ON_FORK will allow userspace to have finer control
> over scheduler attributes of child processes.

[...]