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

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Date:	Tue, 03 May 2011 10:54:00 +0100
From:	Colin Ian King <colin.king@...onical.com>
To:	Mel Gorman <mgorman@...e.de>
Cc:	James Bottomley <James.Bottomley@...e.de>, Jan Kara <jack@...e.cz>,
	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, 2011-04-28 at 18:18 +0100, Mel Gorman wrote:
> On Thu, Apr 28, 2011 at 11:56:17AM -0500, James Bottomley wrote:
> > On Thu, 2011-04-28 at 11:50 -0500, James Bottomley wrote:
> > > This is the output of perf record -g -a -f sleep 5
> > > 
> > > (hopefully the list won't choke)
> > 
> > Um, this one actually shows kswapd
> > 
> > James
> > 
> > ---
> > 
> > # Events: 6K cycles
> > #
> > # Overhead      Command        Shared Object                                   Symbol
> > # ........  ...........  ...................  .......................................
> > #
> >     20.41%      kswapd0  [kernel.kallsyms]    [k] shrink_slab
> >                 |
> >                 --- shrink_slab
> >                    |          
> >                    |--99.91%-- kswapd
> >                    |          kthread
> >                    |          kernel_thread_helper
> >                     --0.09%-- [...]
> > 
> 
> Ok. I can't see how the patch "mm: vmscan: reclaim order-0 and use
> compaction instead of lumpy reclaim" is related unless we are seeing
> two problems that happen to manifest in a similar manner.

That is a distinct possibility.
> 
> However, there were a number of changes made to dcache in particular
> for 2.6.38. Specifically thinks like dentry_kill use trylock and is
> happy to loop around if it fails to acquire anything. See things like
> this for example;
> 
[ text deleted ]

> Way hey, cgroups are also in the mix. How jolly.
> 
> Is systemd a common element of the machines hitting this bug by any
> chance?

Not in my case, using upstart on my machine.
> 
Colin


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