linux-kernel - Re: [PATCH 04/10] mm: slub: add knowledge of reserve pages

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Message-Id: <1187601455.6114.189.camel@twins>
Date:	Mon, 20 Aug 2007 11:17:35 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Pekka J Enberg <penberg@...helsinki.fi>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	David Miller <davem@...emloft.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Daniel Phillips <phillips@...gle.com>,
	Christoph Lameter <clameter@....com>,
	Matt Mackall <mpm@...enic.com>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Steve Dickson <SteveD@...hat.com>
Subject: Re: [PATCH 04/10] mm: slub: add knowledge of reserve pages

On Mon, 2007-08-20 at 12:12 +0300, Pekka J Enberg wrote:
> Hi Peter,
> 
> On Mon, 20 Aug 2007, Peter Zijlstra wrote:
> > -static struct page *new_slab(struct kmem_cache *s, gfp_t flags, int node)
> > +static struct page *new_slab(struct kmem_cache *s, gfp_t flags, int node, int *reserve)
> >  {
> 
> [snip]
> 
> > +	*reserve = page->reserve;
> 
> Any reason why the callers that are actually interested in this don't do 
> page->reserve on their own?

because new_slab() destroys the content?

struct page {
	...
	union {
		pgoff_t index;		/* Our offset within mapping. */
		void *freelist;		/* SLUB: freelist req. slab lock */
		int reserve;		/* page_alloc: page is a reserve page */
		atomic_t frag_count;	/* skb fragment use count */
	};
	...
};

static struct page *new_slab(struct kmem_cache *s, gfp_t flags, int node, int *reserve)
{
	...
	*reserve = page->reserve;
	...
	page->freelist = start;
	...
}


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