From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [15/17] SLUB: Support virtual fallback via SLAB_VFALLBACK
Date: Sat, 29 Sep 2007 02:01:41 -0700
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Cc: Christoph Lameter <clameter@sgi.com>,
	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: Peter Zijlstra <a.p.zijlstra@chello.nl>
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On Sat, 29 Sep 2007 10:53:41 +0200 Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:

> 
> On Sat, 2007-09-29 at 10:47 +0200, Peter Zijlstra wrote:
> 
> > Ah, right, that was the detail... all this lumpy reclaim is useless for
> > atomic allocations. And with SLUB using higher order pages, atomic !0
> > order allocations will be very very common.
> > 
> > One I can remember was:
> > 
> >   add_to_page_cache()
> >     radix_tree_insert()
> >       radix_tree_node_alloc()
> >         kmem_cache_alloc()
> > 
> > which is an atomic callsite.
> > 
> > Which leaves us in a situation where we can load pages, because there is
> > free memory, but can't manage to allocate memory to track them.. 
> 
> Ah, I found a boot log of one of these sessions, its also full of
> order-2 OOMs.. :-/

oom-killings, or page allocation failures?  The latter, one hopes.