linux-kernel - Re: page_migration question

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Message-Id: <20090924112838.33414fc6.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Thu, 24 Sep 2009 11:28:38 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Max Laier <max@...e2party.net>, linux-kernel@...r.kernel.org
Subject: Re: page_migration question

On Sun, 20 Sep 2009 08:30:15 -0400 (EDT)
Christoph Lameter <cl@...ux-foundation.org> wrote:

> On Sun, 20 Sep 2009, Max Laier wrote:
> 
> > I read Documentation/vm/page_migration but couldn't find the information I'm
> > looking for.  Specifically, what locks am I supposed to hold/not hold while
> > calling migrate_prep() and migrate_pages()?  Currently migrate_prep() seems to
> > deadlock for reasons beyond me.  Any help appreciated.
> 
> No locks need to be held while calling migrate prep. The pages to be
> migrated must have been isolated from the LRU and a refcount be taken for
> migrate_pages to work. Look at the implementation of sys_migratepages and
> sys_mbind and sys_movepages.
> 

If you find migrate_prep() hangs, please check your other cpus are available to
run workqueue. It calls lru_add_drain_all()=>schedule_on_each_cpu().

Thanks,
-Kame

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