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

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Message-ID: <alpine.LFD.2.02.1203051233440.1945@tux.localdomain>
Date:	Mon, 5 Mar 2012 12:33:49 +0200 (EET)
From:	Pekka Enberg <penberg@...nel.org>
To:	Rafael Aquini <aquini@...hat.com>
cc:	David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Randy Dunlap <rdunlap@...otime.net>,
	Christoph Lameter <cl@...ux-foundation.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 Fri, 2 Mar 2012, Rafael Aquini wrote:

> On Wed, Feb 29, 2012 at 05:26:07PM -0800, David Rientjes wrote:
> > 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.
> 
> Ok, I'll drop the sysctl part then. Pekka?

Yes, please.
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