linux-kernel - Re: [PATCH 2/4] sched: implement __set_cpus

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Message-ID: <4C03A1C0.4020104@kernel.org>
Date:	Mon, 31 May 2010 13:47:12 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	mingo@...e.hu, linux-kernel@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	Mike Galbraith <efault@....de>
Subject: Re: [PATCH 2/4] sched: implement __set_cpus_allowed()

Hello,

On 05/31/2010 12:46 PM, Peter Zijlstra wrote:
> So workers _are_ thread bound and don't migrate, so for those I don't
> see the problem, that is of course until we have to break affinity when
> their CPU goes down, at which point we should clear PF_THREAD_BOUND I
> think.
> 
> For the rescue thread, why not set PF_THREAD_BOUND when its running
> worklets and clear it when done? That way we get extra checking that
> people won't migrate it when its not allowed.
> 
> Does that work, or did I miss something?

The rescuers migrate themselves so should be okay.  I still think it
would be better to migrate back detached workers.  It's a slow path
for sure but there's a big gaping hole between machine-slow and
human-slow and works can be human-slow (ie. hotplug operation not
finished in several minutes).  I'll see if that's implementable w/o
adding an additional interface.

Thanks.

-- 
tejun
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