linux-kernel - Re: [PATCH 04/16] slab: remove nodeid in struct slab

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Message-ID: <20130823064938.GF22605@lge.com>
Date:	Fri, 23 Aug 2013 15:49:39 +0900
From:	Joonsoo Kim <iamjoonsoo.kim@....com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Pekka Enberg <penberg@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/16] slab: remove nodeid in struct slab

On Thu, Aug 22, 2013 at 05:51:58PM +0000, Christoph Lameter wrote:
> On Thu, 22 Aug 2013, Joonsoo Kim wrote:
> 
> > @@ -1099,8 +1098,7 @@ static void drain_alien_cache(struct kmem_cache *cachep,
> >
> >  static inline int cache_free_alien(struct kmem_cache *cachep, void *objp)
> >  {
> > -	struct slab *slabp = virt_to_slab(objp);
> > -	int nodeid = slabp->nodeid;
> > +	int nodeid = page_to_nid(virt_to_page(objp));
> >  	struct kmem_cache_node *n;
> >  	struct array_cache *alien = NULL;
> >  	int node;
> 
> virt_to_page is a relatively expensive operation. How does this affect
> performance?

Previous code, that is virt_to_slab(), already do virt_to_page().
So this doesn't matter at all.

Thanks.

> 
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