From: "Hillf Danton" <hillf.zj@alibaba-inc.com>
To: "'Vincent Guittot'" <vincent.guittot@linaro.org>
Cc: "'Wanpeng Li'" <kernellwp@gmail.com>,
"'Peter Zijlstra'" <peterz@infradead.org>,
"'Ingo Molnar'" <mingo@kernel.org>,
"'linux-kernel'" <linux-kernel@vger.kernel.org>,
"'Preeti U Murthy'" <preeti@linux.vnet.ibm.com>,
"'Morten Rasmussen'" <Morten.Rasmussen@arm.com>,
"'Kamalesh Babulal'" <kamalesh@linux.vnet.ibm.com>
Subject: RE: [PATCH v8 03/10] sched: move cfs task on a CPU with higher capacity
Date: Tue, 04 Nov 2014 20:54:29 +0800 [thread overview]
Message-ID: <011801cff82e$78cd2c90$6a6785b0$@alibaba-inc.com> (raw)
In-Reply-To: <CAKfTPtD6TZ4iHv9wtg-KCkGZriU79ySSxEV3nao2qQacveKAxA@mail.gmail.com>
>
> On 4 November 2014 13:07, Hillf Danton <hillf.zj@alibaba-inc.com> wrote:
> >> >> + /*
> >> >> + * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
> >> >
> >> >
> >> > Why specify one task instead of not less than one?
> >>
> >> if cfs.h_nr_running = 0 (which should not occurs at that point), we
> >> don't need to do more test to check if it's worth moving the task
> >> because there is no task to move.
> >>
> > I wonder if you can please shed light on the case that
> > the dst_cpu is newly idle.
>
> The main problem if we do the test only for newly idle case, is that
> we are not sure to move the task because we must rely on the
> wakeup/sleep sequence of other tasks on an idle CPU in order to trig
> the migration (periodic background task as an example). So we might
> never move the task whereas idle CPUs are available
>
So no task is migrated in the newly idle case, if I understand the
above correctly.
Hillf
next prev parent reply other threads:[~2014-11-04 12:55 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-04 12:07 [PATCH v8 03/10] sched: move cfs task on a CPU with higher capacity Hillf Danton
2014-11-04 12:48 ` Vincent Guittot
2014-11-04 12:54 ` Hillf Danton [this message]
2014-11-04 13:10 ` Vincent Guittot
2014-11-04 13:31 ` Hillf Danton
2014-11-04 16:45 ` Vincent Guittot
-- strict thread matches above, loose matches on Subject: below --
2014-10-31 8:47 [PATCH v8 00/10] sched: consolidation of CPU capacity and usage Vincent Guittot
2014-10-31 8:47 ` [PATCH v8 03/10] sched: move cfs task on a CPU with higher capacity Vincent Guittot
2014-11-04 8:30 ` Wanpeng Li
2014-11-04 9:41 ` Vincent Guittot
2014-11-04 10:42 ` Wanpeng Li
2014-11-04 11:10 ` Vincent Guittot
2014-11-18 10:47 ` Wanpeng Li
2014-11-18 11:00 ` Vincent Guittot
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