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From: Quentin Perret <qperret@google.com>
To: Qais Yousef <qais.yousef@arm.com>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	linux-kernel@vger.kernel.org,
	Valentin Schneider <valentin.schneider@arm.com>,
	Morten Rasmussen <morten.rasmussen@arm.com>
Subject: Re: [PATCH] sched/eas: Don't update misfit status if the task is pinned
Date: Tue, 19 Jan 2021 16:55:16 +0000	[thread overview]
Message-ID: <YAcO9HHHVBx7oBG/@google.com> (raw)
In-Reply-To: <20210119164027.drfpmrol3xhf4ckc@e107158-lin>

On Tuesday 19 Jan 2021 at 16:40:27 (+0000), Qais Yousef wrote:
> On 01/19/21 15:35, Quentin Perret wrote:
> > Do you mean failing the sched_setaffinity syscall if e.g. the task
> > has a min clamp that is higher than the capacity of the CPUs to which it
> > will be pinned? If so, I'm not sure if we really want that.
> 
> No. In Android for instance, I'm worried a background task affined to little
> cores that has a utilization > capacity_of(little) will trigger the same
> problem. It'll be affined to more than just 1 cpu, but none of the little cpus
> will actually fit.
> 
> Makes sense?

Now yes.

I agree this may be a real problem, but capacity_of() very much is a
per-CPU thing, because of RT pressure and such, and that is not a static
thing by any mean. So, even if the task doesn't fit on any CPU _now_ we
might still want to mark it misfit, just so it can be picked up by a
potential idle balance on another CPU later on. Maybe capacity_orig_of
would be preferable?

Thanks,
Quentin

  reply	other threads:[~2021-01-19 18:28 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-19 12:07 [PATCH] sched/eas: Don't update misfit status if the task is pinned Qais Yousef
2021-01-19 12:24 ` Valentin Schneider
2021-01-19 13:34 ` Vincent Guittot
2021-01-19 13:54   ` Valentin Schneider
2021-01-19 14:19     ` Vincent Guittot
2021-01-19 16:55       ` Valentin Schneider
2021-01-19 17:06         ` Vincent Guittot
2021-01-19 15:35 ` Quentin Perret
2021-01-19 16:40   ` Qais Yousef
2021-01-19 16:55     ` Quentin Perret [this message]
2021-01-19 17:42       ` Qais Yousef
2021-01-19 17:50         ` Quentin Perret
2021-01-20 11:57           ` Qais Yousef

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