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From: Peter Zijlstra <peterz@infradead.org>
To: Yun Hsiang <hsiang023167@gmail.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Ingo Molnar <mingo@kernel.org>,
	linux-kernel@vger.kernel.org,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Patrick Bellasi <patrick.bellasi@matbug.net>,
	Qais Yousef <qais.yousef@arm.com>,
	Suren Baghdasaryan <surenb@google.com>
Subject: Re: [PATCH v2] sched/uclamp: Allow to reset a task uclamp constraint value
Date: Tue, 17 Nov 2020 11:23:46 +0100	[thread overview]
Message-ID: <20201117102346.GF3121406@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20201115050521.GA1390370@ubuntu>

On Sun, Nov 15, 2020 at 01:05:21PM +0800, Yun Hsiang wrote:
> Hi Dietmar,
> On Fri, Nov 13, 2020 at 12:34:54PM +0100, Dietmar Eggemann wrote:
> > In case the user wants to stop controlling a uclamp constraint value
> > for a task, use the magic value -1 in sched_util_{min,max} with the
> > appropriate sched_flags (SCHED_FLAG_UTIL_CLAMP_{MIN,MAX}) to indicate
> > the reset.
> > 
> > The advantage over the 'additional flag' approach (i.e. introducing
> > SCHED_FLAG_UTIL_CLAMP_RESET) is that no additional flag has to be
> > exported via uapi. This avoids the need to document how this new flag
> > has be used in conjunction with the existing uclamp related flags.
> > 
> > The following subtle issue is fixed as well. When a uclamp constraint
> > value is set on a !user_defined uclamp_se it is currently first reset
> > and then set.
> > Fix this by AND'ing !user_defined with !SCHED_FLAG_UTIL_CLAMP which
> > stands for the 'sched class change' case.
> > The related condition 'if (uc_se->user_defined)' moved from
> > __setscheduler_uclamp() into uclamp_reset().
> 
> I think this is great, thanks!
> Reviewed-by: Yun Hsiang <hsiang023167@gmail.com>

Thanks!

  reply	other threads:[~2020-11-17 10:24 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-13 11:34 [PATCH v2] sched/uclamp: Allow to reset a task uclamp constraint value Dietmar Eggemann
2020-11-15  5:05 ` Yun Hsiang
2020-11-17 10:23   ` Peter Zijlstra [this message]
2020-11-20 12:34 ` [tip: sched/core] " tip-bot2 for Dietmar Eggemann

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