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

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Message-ID: <4875000A.3060004@sgi.com>
Date:	Wed, 09 Jul 2008 11:14:34 -0700
From:	Mike Travis <travis@....com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Christoph Lameter <cl@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	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

Jeremy Fitzhardinge wrote:
...
> 
> Once the pda has shrunk as much as it can (which remove everything
> except stack_canary, I think), then remove all the X_pda macros, since
> there won't be any users anyway.
> 
>    J

You bring up a good point here.  Since the stack_canary has to be 20
(or is that 0x20?) bytes from %gs, then it sounds like we'll still
need a pda struct of some sort.  And zero padding before that seems
counter-productive, so perhaps taking a poll of the most used pda
(or percpu) variables and keeping them in the same cache line would
be more useful?

Thanks,
Mike
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