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

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Message-ID: <4875281C.4060806@sgi.com>
Date:	Wed, 09 Jul 2008 14:05:32 -0700
From:	Mike Travis <travis@....com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"H. Peter Anvin" <hpa@...or.com>, Jack Steiner <steiner@....com>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC 00/15] x86_64: Optimize percpu accesses

Ingo Molnar wrote:
> * Jeremy Fitzhardinge <jeremy@...p.org> wrote:
> 
>>> What is remaining is the task to rename
>>>
>>> 	pda.Y -> Z
>>>
>>> in order to make variable references the same under both arches. 
>>> Presumably the Z is the corresponding 32 bit variable. There are 
>>> likely a number of cases where the transformation is trivial if we 
>>> just identify the corresponding 32 bit equivalent.
>> Yes, I understand that, but it's still pointless churn.  The 
>> intermediate step is no improvement over what was there before, and 
>> isn't any closer to the desired final result.
>>
>> Once you've made the pda a percpu variable, and redefined all the 
>> X_pda macros in terms of x86_X_percpu, then there's no need to touch 
>> all the usage sites until you're *actually* going to unify something.  
>> Touching them all just because you find "X_pda" unsightly doesn't help 
>> anyone.  Ideally every site you touch will remove a #ifdef 
>> CONFIG_X86_64, or make two as-yet unified pieces of code closer to 
>> unification.
> 
> that makes sense. Does everyone agree on #1-#2-#3 and then gradual 
> elimination of most pda members (without going through an intermediate 
> renaming of pda members) being the way to go?
> 
> 	Ingo


This is fine with me... not much more work required to go "all the way"... ;-)
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