From: Alex Shi <alex.shi@intel.com>
To: Namhyung Kim <namhyung@kernel.org>
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: Fri, 11 Jan 2013 10:36:15 +0800 [thread overview]
Message-ID: <50EF7A9F.8070700@intel.com> (raw)
In-Reply-To: <87k3rlpou5.fsf@sejong.aot.lge.com>
On 01/10/2013 01:52 PM, Namhyung Kim wrote:
> On Wed, 09 Jan 2013 16:34:39 +0800, Alex Shi wrote:
>> On 01/09/2013 03:54 PM, Namhyung Kim wrote:
>>> 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.
>>
>> The old logical will return directly whenever prev_cpu or this cpu idle,
>> but your new logical just has one chance.
>
> Sorry, I can't get your point. Could you elaborate on it a bit more?
Sorry. I misunderstand this.
Acked-by: Alex Shi
>
> Thanks,
> Namhyung
>
--
Thanks Alex
next prev parent reply other threads:[~2013-01-11 2:35 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
2013-01-09 8:34 ` Alex Shi
2013-01-10 5:52 ` Namhyung Kim
2013-01-11 2:36 ` Alex Shi [this message]
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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