linux-kernel - Re: [PATCH -mm] throttle direct reclaim when too many pages are isolated already

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Message-ID: <4A5EA1A4.1080502@redhat.com>
Date:	Wed, 15 Jul 2009 23:42:28 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Wu Fengguang <fengguang.wu@...el.com>
Subject: Re: [PATCH -mm] throttle direct reclaim when too many pages are isolated
 already

Andrew Morton wrote:
> On Wed, 15 Jul 2009 23:28:14 -0400 Rik van Riel <riel@...hat.com> wrote:

>> If we are stuck at this point in the page reclaim code,
>> it is because too many other tasks are reclaiming pages.
>>
>> That makes it fairly safe to just return SWAP_CLUSTER_MAX
>> here and hope that __alloc_pages() can get a page.
>>
>> After all, if __alloc_pages() thinks it made progress,
>> but still cannot make the allocation, it will call the
>> pageout code again.
> 
> Which will immediately return because the caller still has
> fatal_signal_pending()?

Other processes are in the middle of freeing pages at
this point, so we should succeed in __alloc_pages()
fairly quickly (and then die and free all our memory).

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