linux-kernel - Re: [RFC 00/15] x86_64: Optimize percpu accesses

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Message-ID: <48764D19.9000407@zytor.com>
Date:	Thu, 10 Jul 2008 13:55:37 -0400
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Christoph Lameter <cl@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Ingo Molnar <mingo@...e.hu>, Mike Travis <travis@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jack Steiner <steiner@....com>, linux-kernel@...r.kernel.org,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: [RFC 00/15] x86_64: Optimize percpu accesses

Jeremy Fitzhardinge wrote:
> 
>>  Its best to consistently access
>> per cpu variables using the segment registers.
> 
> It is, but initially the segment base is 0, so just using a percpu 
> variable does something sensible from the start with no special setup.
> 

That's easy enough to fix -- synthesizing a GDT entry is trivial enough 
-- but since it currently works, and since the offsets on 32 bits can 
reach the full address space anyway, there is no reason to change.

	-hpa
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