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

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Message-ID: <48752AC2.7080700@zytor.com>
Date:	Wed, 09 Jul 2008 17:16:50 -0400
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Mike Travis <travis@....com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jack Steiner <steiner@....com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC 00/15] x86_64: Optimize percpu accesses

Eric W. Biederman wrote:
> Jeremy Fitzhardinge <jeremy@...p.org> writes:
> 
>>> Or we could do something completely evil.  And use the other segment
>>> register for the stack canary.
>>>
>> That would still require gcc changes, so it doesn't help much.
> 
> We could use %fs for the per cpu variables.  Then we could set %gs to whatever
> we wanted to sync up with gcc

No swapfs instruction, and extra performance penalty because %fs is used 
  in userspace.

	-hpa
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