linux-kernel - Re: [PATCH -mm] throttle direct reclaim when too many pages are isolated already (v3)

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Date:	Wed, 29 Jul 2009 12:19:34 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Pavel Machek <pavel@....cz>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	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 (v3)

Pavel Machek wrote:
> On Wed 2009-07-15 23:53:18, Rik van Riel wrote:
>> When way too many processes go into direct reclaim, it is possible
>> for all of the pages to be taken off the LRU.  One result of this
>> is that the next process in the page reclaim code thinks there are
>> no reclaimable pages left and triggers an out of memory kill.
>>
>> One solution to this problem is to never let so many processes into
>> the page reclaim path that the entire LRU is emptied.  Limiting the
>> system to only having half of each inactive list isolated for
>> reclaim should be safe.
> 
> Is this still racy? Like on 100cpu machine, with LRU size of 50...?

If a 100 CPU system gets down to just 100 reclaimable pages,
getting the OOM killer to trigger sounds desirable.

The goal of this patch is to avoid _false_ OOM kills, when
the system still has enough reclaimable memory available.

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