linux-kernel - Re: [PATCH 09/16] slab: use __GFP_COMP flag for allocating slab pages

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Date:	Fri, 23 Aug 2013 15:55:43 +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 09/16] slab: use __GFP_COMP flag for allocating slab pages

On Thu, Aug 22, 2013 at 06:00:56PM +0000, Christoph Lameter wrote:
> On Thu, 22 Aug 2013, Joonsoo Kim wrote:
> 
> > If we use 'struct page' of first page as 'struct slab', there is no
> > advantage not to use __GFP_COMP. So use __GFP_COMP flag for all the cases.
> 
> Ok that brings it in line with SLUB and SLOB.

Yes!

> 
> > @@ -2717,17 +2701,8 @@ static void slab_put_obj(struct kmem_cache *cachep, struct slab *slabp,
> >  static void slab_map_pages(struct kmem_cache *cache, struct slab *slab,
> >  			   struct page *page)
> >  {
> > -	int nr_pages;
> > -
> > -	nr_pages = 1;
> > -	if (likely(!PageCompound(page)))
> > -		nr_pages <<= cache->gfporder;
> > -
> > -	do {
> > -		page->slab_cache = cache;
> > -		page->slab_page = slab;
> > -		page++;
> > -	} while (--nr_pages);
> > +	page->slab_cache = cache;
> > +	page->slab_page = slab;
> >  }
> 
> And saves some processing.

Yes!

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