linux-kernel - Re: Switch per cpu partial page support off for debugging

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Message-ID: <alpine.LFD.2.02.1112120915030.2555@tux.localdomain>
Date:	Mon, 12 Dec 2011 09:16:19 +0200 (EET)
From:	Pekka Enberg <penberg@...nel.org>
To:	Christoph Lameter <cl@...ux.com>
cc:	Eric Dumazet <eric.dumazet@...il.com>,
	David Rientjes <rientjes@...gle.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Switch per cpu partial page support off for debugging

On Wed, 23 Nov 2011, Christoph Lameter wrote:
> Eric saw an issue with accounting of slabs during validation. Its not
> possible to determine accurately how many per cpu partial slabs exist at
> any time so this switches off per cpu partial pages during debug.
>
> Subject: Switch per cpu partial page support off for debugging
>
> Otherwise we have accounting issues.
>
> Signed-off-by: Christoph Lameter <cl@...ux.com>
>
>
> ---
> mm/slub.c |    4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> Index: linux-2.6/mm/slub.c
> ===================================================================
> --- linux-2.6.orig/mm/slub.c	2011-11-22 11:57:21.000000000 -0600
> +++ linux-2.6/mm/slub.c	2011-11-22 11:57:55.000000000 -0600
> @@ -3027,7 +3027,9 @@ static int kmem_cache_open(struct kmem_c
> 	 *    per node list when we run out of per cpu objects. We only fetch 50%
> 	 *    to keep some capacity around for frees.
> 	 */
> -	if (s->size >= PAGE_SIZE)
> +	if (kmem_cache_debug(s))
> +		s->cpu_partial = 0;
> +	else if (s->size >= PAGE_SIZE)
> 		s->cpu_partial = 2;
> 	else if (s->size >= 1024)
> 		s->cpu_partial = 6;

Looks OK to me. CC'ing Eric and David.
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