Date: Thu, 19 Jan 2006 14:15:15 -0800
From: Andrew Morton <akpm@osdl.org>
To: Dave Jones <davej@redhat.com>
Cc: AChittenden@bluearc.com, linux-kernel@vger.kernel.org, lwoodman@redhat.com,
       Jens Axboe <axboe@suse.de>
Subject: Re: Out of Memory: Killed process 16498 (java).
Message-Id: <20060119141515.5f779b8d.akpm@osdl.org>
In-Reply-To: <20060119194836.GM21663@redhat.com>
References: <89E85E0168AD994693B574C80EDB9C270355601F@uk-email.terastack.bluearc.com>
	<20060119194836.GM21663@redhat.com>
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Dave Jones <davej@redhat.com> wrote:
>
> On Thu, Jan 19, 2006 at 03:11:45PM -0000, Andy Chittenden wrote:
>  > DMA free:20kB min:24kB low:28kB high:36kB active:0kB inactive:0kB
>  > present:12740kB pages_scanned:4 all_unreclaimable? yes
> 
> Note we only scanned 4 pages before we gave up.
> Larry Woodman came up with this patch below that clears all_unreclaimable
> when in two places where we've made progress at freeing up some pages
> which has helped oom situations for some of our users.

That won't help - there are exactly zero pages on ZONE_DMA's LRU.

The problem appears to be that all of the DMA zone has been gobbled up by
the BIO layer.  It seems quite inappropriate that a modern 64-bit machine
is allocating tons of disk I/O pages from the teeny ZONE_DMA.  I'm
suspecting that someone has gone and set a queue's ->bounce_gfp to the wrong
thing.

Jens, would you have time to investigate please?
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