linux-kernel - Re: [PATCH tip:x86/mm] x86-64, NUMA: Remove custom phys_to

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Date:	Thu, 31 Mar 2011 09:31:01 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Tejun Heo <tj@...nel.org>
cc:	Ingo Molnar <mingo@...hat.com>, Yinghai Lu <yinghai@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH tip:x86/mm] x86-64, NUMA: Remove custom phys_to_nid()
 implementation

On Thu, 31 Mar 2011, Tejun Heo wrote:

> However, with SPARSE memory model, the nid is encoded in page flags.
> The perfect hash implementation was for DISCONTIG memory model which
> got removed years ago by b263295dbf (x86: 64-bit, make sparsemem
> vmemmap the only memory model).

Most memory models have the nid either in page flags or you can get it
from the zone that a page belongs to. So after boot its easy to
determine the node. However, at early boot the page flags may be
initialized relatively late. early_pfn_to_nid does use the early node map
to determine the node and not the page flags. You are switching to
the generic implementation of __pfn_to_nid and dropping the duplicate arch
logic.

Reviewed-by: Christoph Lameter <cl@...ux.com>

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