Re: [PATCH] stop_machine: disable preempt in stop machine path

From: Xiao Guangrong
Date: Wed Sep 16 2009 - 21:24:32 EST




Andrew Morton wrote:
> On Wed, 16 Sep 2009 15:26:54 +0800
> Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxx> wrote:
>
>> We can disable preempt in stop_cpu(), It can reduce the cpu's waiting time
>> and make stop_machine path faster.
>>
>
> "it can"? But does it? Are there any measurements or observations to
> back this up?
>
> The kstop threads are already created with create_rt_workqueue() (which
> has super-secret undocumented semantics which I have cleverly
> discovered mean "use SCHED_FIFO").
>

Ah, indeed, please ignore this mail, sorry for bother you all.

Thanks,
Xiao

> So we won't be getting preempted here anyway?
>
>
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