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

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Date:	Wed, 09 Jul 2008 14:37:26 -0400
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Mike Travis <travis@....com>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Jack Steiner <steiner@....com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC 00/15] x86_64: Optimize percpu accesses

Christoph Lameter wrote:
> Jeremy Fitzhardinge wrote:
> 
>> Eh?  Yes they will.  That's the whole point of making the pda a percpu
>> variable itself.  You can use %gs:<small> to get to the pda, and
>> %gs:<larger> to get to percpu variables.  Converting pda->percpu will
>> just have the effect of increasing the %gs offset into the percpu space.
> 
> Right that is what this patchset does.
> 
>> This project isn't interesting to me unless per-cpu variables are
>> directly accessible off %gs.
> 
> Maybe I misunderstood but it seems that you proposed to convert individual members of the pda structure (which uses GS) to per cpu variables (which without this patchset cannot use GS).
> 

I don't understand the "individual members" requirement here.

	-hpa
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