linux-kernel - Re: [PATCH v2 04/10] slab: defer slab_destroy in free

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Message-ID: <alpine.DEB.2.02.1405071801040.1128@chino.kir.corp.google.com>
Date:	Wed, 7 May 2014 18:01:50 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
cc:	Pekka Enberg <penberg@...nel.org>,
	Christoph Lameter <cl@...ux.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Joonsoo Kim <js1304@...il.com>
Subject: Re: [PATCH v2 04/10] slab: defer slab_destroy in free_block()

On Wed, 7 May 2014, Joonsoo Kim wrote:

> In free_block(), if freeing object makes new free slab and number of
> free_objects exceeds free_limit, we start to destroy this new free slab
> with holding the kmem_cache node lock. Holding the lock is useless and,
> generally, holding a lock as least as possible is good thing. I never
> measure performance effect of this, but we'd be better not to hold the lock
> as much as possible.
> 
> Commented by Christoph:
>   This is also good because kmem_cache_free is no longer called while
>   holding the node lock. So we avoid one case of recursion.
> 
> Acked-by: Christoph Lameter <cl@...ux.com>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>

Acked-by: David Rientjes <rientjes@...gle.com>

Nice optimization.  I think it could have benefited from a comment 
describing what the free_block() list formal is, though.
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