linux-kernel - Re: [RFC] NUMA : could we introduce virt_to

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Message-ID: <Pine.LNX.4.64.0703230749130.29603@graphe.net>
Date:	Fri, 23 Mar 2007 07:50:28 -0700 (PDT)
From:	Christoph Lameter <christoph@...eter.com>
To:	Eric Dumazet <dada1@...mosbay.com>
cc:	Andi Kleen <andi@...stfloor.org>,
	Pekka J Enberg <penberg@...helsinki.fi>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] NUMA : could we introduce virt_to_nid() ?

On Fri, 23 Mar 2007, Eric Dumazet wrote:

> Checking Christoph quicklist implementation, I found the same cache miss in free() than SLAB has.
> 
> /* common implementation *
> int virt_to_nid(const void *addr)
> {
> 	struct page *page = virt_to_page(addr); 
> 	return page_to_nid(page);
> }
> 
> On some platforms (x86_64 for example), could we have a better 
> implementation, not accessing struct page, but using phys_to_nid() ?

This is going to pollute the caches since we then use multiple ways to 
determine the node of a page. Its better to stay with the same approach 
for all pages. The page struct is used for many other purposes as well. 
Its likely to be in the cpu cache.


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