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

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Message-ID: <4AB18F8C.1060104@cn.fujitsu.com>
Date:	Thu, 17 Sep 2009 09:23:24 +0800
From:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	mingo@...e.hu, rusty@...tcorp.com.au, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] stop_machine: disable preempt in stop machine path



Andrew Morton wrote:
> On Wed, 16 Sep 2009 15:26:54 +0800
> Xiao Guangrong <xiaoguangrong@...fujitsu.com> 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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