linux-kernel - Re: [PATCH] mm: SLAB Out-of-memory diagnostics

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Message-ID: <alpine.DEB.2.00.1202291724100.17729@chino.kir.corp.google.com>
Date:	Wed, 29 Feb 2012 17:26:07 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Rafael Aquini <aquini@...hat.com>
cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Randy Dunlap <rdunlap@...otime.net>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>, Rik van Riel <riel@...hat.com>,
	Josef Bacik <josef@...hat.com>
Subject: Re: [PATCH] mm: SLAB Out-of-memory diagnostics

On Wed, 29 Feb 2012, Rafael Aquini wrote:

> Following the example at mm/slub.c, add out-of-memory diagnostics to the SLAB
> allocator to help on debugging OOM conditions. This patch also adds a new
> sysctl, 'oom_dump_slabs_forced', that overrides the effect of __GFP_NOWARN page
> allocation flag and forces the kernel to report every slab allocation failure.
> 
> An example print out looks like this:
> 
>   <snip page allocator out-of-memory message>
>   SLAB: Unable to allocate memory on node 0 (gfp=0x11200)
>      cache: bio-0, object size: 192, order: 0
>      node0: slabs: 3/3, objs: 60/60, free: 0
> 
> Signed-off-by: Rafael Aquini <aquini@...hat.com>

I like it, except for the addition of the sysctl.  __GFP_NOWARN is used 
for a reason, usually because whatever is allocating memory can gracefully 
handle a failure and should not be emitted to the kernel log under any 
circumstances.
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