linux-kernel - Re: [RFC, PATCH] SLAB : [NUMA] keep nodeid in struct page instead of struct slab

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Message-Id: <20070321165230.257c61d1.dada1@cosmosbay.com>
Date:	Wed, 21 Mar 2007 16:52:30 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	"Pekka Enberg" <penberg@...helsinki.fi>
Cc:	"Christoph Lameter" <christoph@...eter.com>,
	"Andi Kleen" <andi@...stfloor.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"linux kernel" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC, PATCH] SLAB : [NUMA] keep nodeid in struct page instead
 of struct slab

On Wed, 21 Mar 2007 17:47:13 +0200
"Pekka Enberg" <penberg@...helsinki.fi> wrote:

> On 3/21/07, Eric Dumazet <dada1@...mosbay.com> wrote:
> > Last time I checked 'struct page', they was no nodeid in it.
> 
> Hmm, page_to_nid() in include/linx/mm.h doesn't agree with you:
> 
> #ifdef NODE_NOT_IN_PAGE_FLAGS
> extern int page_to_nid(struct page *page);
> #else
> static inline int page_to_nid(struct page *page)
> {
>         return (page->flags >> NODES_PGSHIFT) & NODES_MASK;
> }
> #endif
> 

Correct, but still another ifdef NODE_NOT_IN_PAGE_FLAGS

Anyway the correct path is to check GFP_THISNODE stuff, because we can
even avoid access to 'struct page' to get the nodeid, at least on x86_64 NUMA,
where struct memnode can provide the information with less cache footprint.

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