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

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Date:	Tue, 10 May 2011 15:35:09 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
Cc:	Mel Gorman <mgorman@...ell.com>, Jan Kara <jack@...e.cz>,
	colin.king@...onical.com, 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>
Subject: Re: [BUG] fatal hang untarring 90GB file, possibly writeback related.

On Tue, May 10, 2011 at 09:01:04AM -0500, James Bottomley wrote:
> On Tue, 2011-05-10 at 11:21 +0100, Mel Gorman wrote:
> > I really would like to hear if the fix makes a big difference or
> > if we need to consider forcing SLUB high-order allocations bailing
> > at the first sign of trouble (e.g. by masking out __GFP_WAIT in
> > allocate_slab). Even with the fix applied, kswapd might be waking up
> > less but processes will still be getting stalled in direct compaction
> > and direct reclaim so it would still be jittery.
> 
> "the fix" being this
> 
> https://lkml.org/lkml/2011/3/5/121
> 

Drop this for the moment. It was a long shot at best and there is little
evidence the problem is in this area.

I'm attaching two patches. The first is the NO_KSWAPD one to stop
kswapd being woken up by SLUB using speculative high-orders. The second
one is more drastic and prevents slub entering direct reclaim or
compaction. It applies on top of patch 1. These are both untested and
afraid are a bit rushed as well :(

-- 
Mel Gorman
SUSE Labs

View attachment "mm-slub-do-not-wake-kswapd-for-slub-high-orders.patch" of type "text/x-patch" (1395 bytes)

View attachment "mm-slub-do-not-take-expensive-steps-for-slub-high-orders.patch" of type "text/x-patch" (2401 bytes)