Re: [S+Q2 00/19] SLUB with queueing (V2) beats SLAB netperf TCP_RR

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: David Rientjes <rientjes@google.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>,
	Christoph Lameter <cl@linux-foundation.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Nick Piggin <npiggin@suse.de>
Subject: Re: [S+Q2 00/19] SLUB with queueing (V2) beats SLAB netperf TCP_RR
Date: Mon, 19 Jul 2010 10:16:44 +1000	[thread overview]
Message-ID: <1279498604.10390.1775.camel@pasglop> (raw)
In-Reply-To: <alpine.DEB.2.00.1007160158540.18388@chino.kir.corp.google.com>

On Fri, 2010-07-16 at 02:02 -0700, David Rientjes wrote:
> On Fri, 16 Jul 2010, Pekka Enberg wrote:
> 
> > > I'd also consider patch 7 for 2.6.35-rc6 (and -stable).
> > 
> > It's an obvious bug fix but is it triggered in practice? Is there a bugzilla
> > report for that?
> > 
> 
> Let's ask Benjamin who initially reported the problem with arch_initcall 
> whether or not this is rc (and stable) material.
> 
> For reference, we're talking about the sysfs_slab_remove() check on 
> slab_state to prevent the WARN in the kobject code you hit with its fix 
> below:

The only case where I reproduce that is an in-house kernel port that we
haven't published yet so it doesn't have to be -stable material as far
as I'm concerned.

Cheers,
Ben.

> 
> From: Christoph Lameter <cl@linux-foundation.org>
> 
> slub: Allow removal of slab caches during boot
> 
> If a slab cache is removed before we have setup sysfs then simply skip over
> the sysfs handling.
> 
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Roland Dreier <rdreier@cisco.com>
> Signed-off-by: Christoph Lameter <cl@linux-foundation.org>
> 
> ---
>  mm/slub.c |    7 +++++++
>  1 file changed, 7 insertions(+)
> 
> Index: linux-2.6/mm/slub.c
> ===================================================================
> --- linux-2.6.orig/mm/slub.c	2010-07-06 15:13:48.000000000 -0500
> +++ linux-2.6/mm/slub.c	2010-07-06 15:15:27.000000000 -0500
> @@ -4507,6 +4507,13 @@ static int sysfs_slab_add(struct kmem_ca
>  
>  static void sysfs_slab_remove(struct kmem_cache *s)
>  {
> +	if (slab_state < SYSFS)
> +		/*
> +		 * Sysfs has not been setup yet so no need to remove the
> +		 * cache from sysfs.
> +		 */
> +		return;
> +
>  	kobject_uevent(&s->kobj, KOBJ_REMOVE);
>  	kobject_del(&s->kobj);
>  	kobject_put(&s->kobj);
> 
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