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

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Message-ID: <20080709192822.GB4804@elte.hu>
Date:	Wed, 9 Jul 2008 21:28:22 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Mike Travis <travis@....com>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Jack Steiner <steiner@....com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC 00/15] x86_64: Optimize percpu accesses


* Mike Travis <travis@....com> wrote:

>   * x86_64: Rebase per cpu variables to zero
> 
>     Take advantage of the zero-based per cpu area provided above. Then 
>     we can directly use the x86_32 percpu operations. x86_32 offsets 
>     %fs by __per_cpu_start. x86_64 has %gs pointing directly to the 
>     pda and the per cpu area thereby allowing access to the pda with 
>     the x86_64 pda operations and access to the per cpu variables 
>     using x86_32 percpu operations.

hm, have the binutils (or gcc) problems with this been resolved?

If common binutils versions miscompile the kernel with this feature then 
i guess we cannot just unconditionally enable it. (My hope is that it's 
not necessarily a binutils bug but some broken assumption of the kernel 
somewhere.)

	Ingo
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