From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [15/17] SLUB: Support virtual fallback via SLAB_VFALLBACK
Date: Fri, 28 Sep 2007 19:55:19 +0200
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Cc: Nick Piggin <nickpiggin@yahoo.com.au>,
	Christoph Hellwig <hch@lst.de>, Mel Gorman <mel@skynet.ie>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	David Chinner <dgc@sgi.com>, Jens Axboe <jens.axboe@oracle.com>
To: Christoph Lameter <clameter@sgi.com>
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On Fri, 2007-09-28 at 10:33 -0700, Christoph Lameter wrote:

> Again I have not seen any fallbacks to vmalloc in my testing. What we are 
> doing here is mainly to address your theoretical cases that we so far have 
> never seen to be a problem and increase the reliability of allocations of
> page orders larger than 3 to a usable level. So far I have so far not 
> dared to enable orders larger than 3 by default.

take a recent -mm kernel, boot with mem=128M.

start 2 processes that each mmap a separate 64M file, and which does
sequential writes on them. start a 3th process that does the same with
64M anonymous.

wait for a while, and you'll see order=1 failures.