Message-ID: <4875000A.3060004@sgi.com>
Date: Wed, 09 Jul 2008 11:14:34 -0700
From: Mike Travis <travis@sgi.com>
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To: Jeremy Fitzhardinge <jeremy@goop.org>
CC: Christoph Lameter <cl@linux-foundation.org>, Ingo Molnar <mingo@elte.hu>,
       Andrew Morton <akpm@linux-foundation.org>,
       "Eric W. Biederman" <ebiederm@xmission.com>,
       "H. Peter Anvin" <hpa@zytor.com>, Jack Steiner <steiner@sgi.com>,
       linux-kernel@vger.kernel.org
Subject: Re: [RFC 00/15] x86_64: Optimize percpu accesses
References: <20080709165129.292635000@polaris-admin.engr.sgi.com> <4874F4F2.9010603@goop.org> <4874F7D9.5060607@linux-foundation.org> <4874FAB2.5080401@goop.org>
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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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