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Date: Fri, 16 Mar 2007 13:15:38 -0700 (PDT)
From: Christoph Lameter <clameter@sgi.com>
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To: Andi Kleen <andi@firstfloor.org>
cc: Steven Rostedt <rostedt@goodmis.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Martin Bligh <mbligh@mbligh.org>, Ingo Molnar <mingo@elte.hu>,
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       Chris Wright <chrisw@sous-sol.org>,
       Rusty Russell <rusty@rustcorp.com.au>,
       Glauber de Oliveira Costa <glommer@gmail.com>
Subject: Re: [PATCH 00/18] Make common x86 arch area for i386 and x86_64 -
 Take 2
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On Fri, 16 Mar 2007, Andi Kleen wrote:

> 
> > x86_64 is going to acquire more functionality that will not be available 
> > for i386. We plan f.e. to add virtual memmap support for x86_64. Virtual 
> 
> What advantage would that have over the current setup?
> We already should handle holes between nodes reasonably efficiently
> and with nonlinear memory even holes inside nodes shouldn't be a problem.

It is primarily a performance improvement since the sparsemem table 
lookups would no longer be necessary and it also streamlines other 
frequent cacheline uses. These page -> page_struct and vice versa 
operations are key to the performance of various subsystem among them 
the slab allocator.