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From: Namhyung Kim <namhyung@kernel.org>
To: Alex Shi <alex.shi@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	LKML <linux-kernel@vger.kernel.org>,
	Namhyung Kim <namhyung.kim@lge.com>,
	Mike Galbraith <efault@gmx.de>,
	Preeti U Murthy <preeti@linux.vnet.ibm.com>,
	Vincent Guittot <vincent.guittot@linaro.org>
Subject: Re: [PATCH] sched: Get rid of unnecessary checks from select_idle_sibling
Date: Wed, 09 Jan 2013 16:54:09 +0900	[thread overview]
Message-ID: <876236rdum.fsf@sejong.aot.lge.com> (raw)
In-Reply-To: <50ED1D54.70208@intel.com> (Alex Shi's message of "Wed, 09 Jan 2013 15:33:40 +0800")

Hi Alex,

On Wed, 09 Jan 2013 15:33:40 +0800, Alex Shi wrote:
> On 01/09/2013 02:50 PM, Namhyung Kim wrote:
>> From: Namhyung Kim <namhyung.kim@lge.com>
>> 
>> AFAICS @target cpu of select_idle_sibling() is always either prev_cpu
>> or this_cpu.  So no need to check it again and the conditionals can be
>> consolidated.
[snip]
> Uh, we don't know if the target is this_cpu or previous cpu, If we just
> check the target idle status, we may miss another idle cpu. So this
> patch change the logical in this function.

select_idle_sibling() is called only in select_task_rq_fair() if it
found a suitable affine_sd.  The default target is the 'prev_cpu' of the
task but if wake_affine() returns true it'd be (this) 'cpu'.

I cannot see where the prev_cpu or the cpu is set to another one before
calling select_idle_sibling.

Thanks,
Namhyung

  parent reply	other threads:[~2013-01-09  7:54 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-01-09  6:50 [PATCH] sched: Get rid of unnecessary checks from select_idle_sibling Namhyung Kim
2013-01-09  7:33 ` Alex Shi
2013-01-09  7:38   ` Alex Shi
2013-01-09  8:00     ` Namhyung Kim
2013-01-09  7:54   ` Namhyung Kim [this message]
2013-01-09  8:34     ` Alex Shi
2013-01-10  5:52       ` Namhyung Kim
2013-01-11  2:36         ` Alex Shi
2013-01-09  8:21 ` Preeti U Murthy
2013-01-10  5:49   ` Namhyung Kim
2013-01-10  8:19     ` Preeti U Murthy

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