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From: Jiang Biao <benbjiang@gmail.com>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Jiang Biao <humjb_1983@163.com>, Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Jiang Biao <benbjiang@tencent.com>
Subject: Re: [PATCH] sched/fair: consider sched-idle CPU when selecting idle core
Date: Fri, 24 Jul 2020 16:12:35 +0800	[thread overview]
Message-ID: <CAPJCdBnv4W5+u6OZ4vbAdJ2U8ubhfAU7+Zt0JUFjfxKEDuGJSw@mail.gmail.com> (raw)
In-Reply-To: <CAKfTPtCnewaivay7bftUY27+-qB=ct3eSNEoZW=-2Z6k0S4B4Q@mail.gmail.com>

On Fri, 24 Jul 2020 at 15:24, Vincent Guittot
<vincent.guittot@linaro.org> wrote:
>
> On Fri, 24 Jul 2020 at 01:39, Jiang Biao <humjb_1983@163.com> wrote:
> >
> > From: Jiang Biao <benbjiang@tencent.com>
> >
> > Sched-idle CPU has been considered in select_idle_cpu and
> > select_idle_smt, it also needs to be considered in select_idle_core to
> > be consistent and keep the same *idle* policy.
>
> In the case of select_idle_core, we are looking for a core that is
> fully idle but if one CPU of the core is running a sched_idle task,
> the core will not be idle and we might end up having  the wakeup task
> on a CPU and a sched_idle task on another CPU of the core which is not
> what we want
Got it. sched_idle task may interfere its sibling, which brings me
another question,
If there's a core with smt1 running sched_idle task and smt2 idle,
selecting smt1
rather than smt2 should be more helpful for wakee task, because wakee task
could suppress the sched_idle task without neighbour interfering.
And there seems to be no consideration about that currently.
Is it worth improving that?

Thanks a lot.

Regards,
Jiang

  reply	other threads:[~2020-07-24  8:12 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-23 23:38 [PATCH] sched/fair: consider sched-idle CPU when selecting idle core Jiang Biao
2020-07-24  7:23 ` Vincent Guittot
2020-07-24  8:12   ` Jiang Biao [this message]
2020-07-24 10:33     ` Vincent Guittot
2020-07-24 11:53       ` Jiang Biao
2020-07-24 12:36         ` Ingo Molnar
2020-07-24 12:40           ` Jiang Biao

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