linux-kernel - Re: [PATCH 1/2] SLUB: Out-of-memory diagnostics

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Date:	Thu, 11 Jun 2009 12:51:44 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Mel Gorman <mel@....ul.ie>
Cc:	linux-kernel@...r.kernel.org, cl@...ux-foundation.org,
	Larry.Finger@...inger.net
Subject: Re: [PATCH 1/2] SLUB: Out-of-memory diagnostics

Hi Mel,

On Thu, 2009-06-11 at 10:47 +0100, Mel Gorman wrote:
> On Thu, Jun 11, 2009 at 11:43:46AM +0300, Pekka J Enberg wrote:
> > From: Pekka Enberg <penberg@...helsinki.fi>
> > 
> > As suggested by Mel Gorman, add out-of-memory diagnostics to the SLUB allocator
> > to make debugging OOM conditions easier.
> 
> Picky - make debugging page allocation failures easier. OOM in this
> context might be conflated with the OOM-killer.
> 
> > This patch helped hunt down a nasty
> > OOM issue that popped up every now that was caused by SLUB debugging code which
> > forced 4096 byte allocations to use order 1 pages even in the fallback case.
> > 
> > An example print out looks like this:
> > 
> >   <snip page allocator out-of-memory message>
> >   SLUB: Unable to allocate memory on node -1 (gfp=20)
> 
> node -1 is an implementation detail. Can it print "current" instead? No
> biggie, I know what it means and I suppose anyone debugging an allocation
> failure will know too.

I'd rather keep it as-is because as you say anyone debugging an
allocation failure will know what it means.

On Thu, 2009-06-11 at 10:47 +0100, Mel Gorman wrote:
> gfp is in hex right so gfp=0x20? gfp=20 might have someone thinking it's
> the decimal value.

Fixed. Thanks!

			Pekka

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