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

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Message-ID: <48765006.4020505@zytor.com>
Date:	Thu, 10 Jul 2008 14:08:06 -0400
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Ingo Molnar <mingo@...e.hu>, Mike Travis <travis@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	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

Eric W. Biederman wrote:
> 
> Another alternative that almost fares better then a segment with
> a base of zero is a base of -32K or so.  Only trouble that would get us
> manually managing the per cpu area size again.
> 

Yes, an extra link pass would be better than that.  I have tried, and 
none of the clever things I tried actually works, since GNU ld has 
pretty much no way to get it to reveal its information ahead of time.

However, I want to explore the details of the supposed toolchain issue; 
it might be just a simple tweak to the way things are done now to fix it.

Clearly, given the stack protector ABI, we want %gs:40 to be usable and 
free.

	-hpa
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