linux-kernel - Re: [PATCH 12/12] vmscan: Do not writeback pages in direct reclaim

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Message-ID: <4C181AFD.5060503@redhat.com>
Date:	Tue, 15 Jun 2010 20:29:49 -0400
From:	Rik van Riel <riel@...hat.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
CC:	Mel Gorman <mel@....ul.ie>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
	Dave Chinner <david@...morbit.com>,
	Chris Mason <chris.mason@...cle.com>,
	Nick Piggin <npiggin@...e.de>,
	Johannes Weiner <hannes@...xchg.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 12/12] vmscan: Do not writeback pages in direct reclaim

On 06/15/2010 08:17 PM, KAMEZAWA Hiroyuki wrote:
> On Tue, 15 Jun 2010 15:16:01 +0100
> Mel Gorman<mel@....ul.ie>  wrote:

>> But in turn, where is mem_cgroup_hierarchical_reclaim called from direct
>> reclaim? It appears to be only called from the fault path or as a result
>> of the memcg changing size.
>>
> yes. It's only called from
> 	- page fault
> 	- add_to_page_cache()
>
> I think we'll see no stack problem. Now, memcg doesn't wakeup kswapd for
> reclaiming memory, it needs direct writeback.

Of course, a memcg page fault could still be triggered
from copy_to_user or copy_from_user, with a fairly
arbitrary stack frame above...

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