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

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Date:	Fri, 23 Mar 2007 10:19:32 -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:

> Sorry ? page structs are not in cpu cache at all.

They are if they are in any way handled by the VM.
 
> You carefully commented your alloc() function saying it is touching two cache lines.
> But you omited to say that free() function needs 3 cache lines if CONFIG_NUMA

Yes it needs the third cacheline to check the node of the page in the NUMA 
case.

> For SLAB use, page struct is needed because we use lru.{next|prev} to 
> store slab/cachep pointers, but for a pure page allocator, unless I 
> misread your patch, we dont need it, if virt_to_nid() can do its job 
> without it.

The page allocator is only handling page_structs.
 
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