Re: [PATCH] sched: Get rid of unnecessary checks from select_idle_sibling

[Namhyung Kim]

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@xxxxxxx>
>> 
>> 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
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