From: Mel Gorman <mgorman@suse.de>
Subject: Re: [BUG] fatal hang untarring 90GB file, possibly writeback related.
Date: Fri, 6 May 2011 16:44:44 +0100
Message-ID: <20110506154444.GG6591@suse.de>
References: <20110428171826.GZ4658@suse.de>
 <1304015436.2598.19.camel@mulgrave.site>
 <20110428192104.GA4658@suse.de>
 <1304020767.2598.21.camel@mulgrave.site>
 <1304025145.2598.24.camel@mulgrave.site>
 <1304030629.2598.42.camel@mulgrave.site>
 <20110503091320.GA4542@novell.com>
 <1304431982.2576.5.camel@mulgrave.site>
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 <20110506074224.GB6591@suse.de>
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Cc: Mel Gorman <mgorman@novell.com>, Jan Kara <jack@suse.cz>,
	colin.king@canonical.com, Chris Mason <chris.mason@oracle.com>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	linux-ext4 <linux-ext4@vger.kernel.org>
To: James Bottomley <James.Bottomley@suse.de>
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On Fri, May 06, 2011 at 08:42:24AM +0100, Mel Gorman wrote:
> 
> 1. High-order allocations? You machine is using i915 and RPC, something
>    neither of my test machine uses. i915 is potentially a source for
>    high-order allocations. I'm attaching a perl script. Please run it as
>    ./watch-highorder.pl --output /tmp/highorders.txt
>    while you are running tar. When kswapd is running for about 30
>    seconds, interrupt it with ctrl+c twice in quick succession and
>    post /tmp/highorders.txt
> 

Colin send me this information for his test case at least and I see

11932 instances order=1 normal gfp_flags=GFP_NOWARN|GFP_NORETRY|GFP_COMP|GFP_NOMEMALLOC
 => alloc_pages_current+0xa5/0x110 <ffffffff81149ef5>
 => new_slab+0x1f5/0x290 <ffffffff81153645>
 => __slab_alloc+0x262/0x390 <ffffffff81155192>
 => kmem_cache_alloc+0x115/0x120 <ffffffff81155ab5>
 => mempool_alloc_slab+0x15/0x20 <ffffffff8110e705>
 => mempool_alloc+0x59/0x140 <ffffffff8110ea49>
 => bio_alloc_bioset+0x3e/0xf0 <ffffffff811976ae>
 => bio_alloc+0x15/0x30 <ffffffff81197805>

Colin and James: Did you happen to switch from SLAB to SLUB between
2.6.37 and 2.6.38? My own tests were against SLAB which might be why I
didn't see the problem. Am restarting the tests with SLUB.

-- 
Mel Gorman
SUSE Labs

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