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Message-ID: <4B1E195D.50802@kernel.org>
Date: Tue, 08 Dec 2009 18:16:13 +0900
From: Tejun Heo <tj@...nel.org>
To: Peter Zijlstra <peterz@...radead.org>
CC: tglx@...utronix.de, mingo@...e.hu, avi@...hat.com, efault@....de,
rusty@...tcorp.com.au, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/7] sched: implement try_to_wake_up_local()
Hello,
On 12/08/2009 05:53 PM, Peter Zijlstra wrote:
> On Mon, 2009-12-07 at 19:27 +0900, Tejun Heo wrote:
>>
>>> What happens when you run out of memory and the workqueue progress is
>>> needed to get free memory?
>>
>> That's when the "rescuer" workers kick in. All workqueues which might
>> be used during allocation paths are required to have one. When
>> manager fails to fork a new worker, it summons the rescuers. They
>> migrate to the distressed cpu and processes only the works from their
>> specific workqueues thus guaranteeing forward progress.
>
> What happens if the rescue worker is tied up on another cpu in a
> deadlock avoidance game, which requires progress on this cpu in order to
> resolve it?
Hmmm.... I think one rescuer thread per a workqueue is enough to
guarantee forward-progress. If there are workqueues which have
inter-cpu dependency, we'll probably need per-cpu rescuers but is
there any?
Thanks.
--
tejun
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