linux-ext4 - Re: [BUG] fatal hang untarring 90GB file, possibly writeback related.

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Date:	Thu, 28 Apr 2011 15:07:25 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Jan Kara <jack@...e.cz>
Cc:	colin.king@...onical.com,
	James Bottomley <James.Bottomley@...e.de>,
	Chris Mason <chris.mason@...cle.com>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-ext4 <linux-ext4@...r.kernel.org>, mgorman@...ell.com
Subject: Re: [BUG] fatal hang untarring 90GB file, possibly writeback related.

On Thu, Apr 28, 2011 at 03:52:28PM +0200, Jan Kara wrote:
> On Thu 28-04-11 12:36:30, Colin Ian King wrote:
> > One more data point to add, I've been looking at an identical issue when
> > copying large amounts of data.  I bisected this - and the lockups occur
> > with commit 
> > 3e7d344970673c5334cf7b5bb27c8c0942b06126 - before that I don't see the
> > issue. With this commit, my file copy test locks up after ~8-10
> > iterations, before this commit I can copy > 100 times and don't see the
> > lockup.
>   Adding Mel to CC, I guess he'll be interested. Mel, it seems this commit
> of yours causes kswapd on non-preempt kernels spin for a *long* time...
> 

I'm still thinking about the traces which do not point the finger
directly at compaction per-se but it's possible that the change means
kswapd is not reclaiming like it should be.

To test this theory, does applying
[d527caf2: mm: compaction: prevent kswapd compacting memory to reduce
CPU usage] help?

-- 
Mel Gorman
SUSE Labs
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