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

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Date:	Thu, 10 Jul 2008 10:20:39 -0700
From:	Mike Travis <travis@....com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Jack Steiner <steiner@....com>, linux-kernel@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [RFC 00/15] x86_64: Optimize percpu accesses

H. Peter Anvin wrote:
> Mike Travis wrote:
>> 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.
>>
>> One thing to remember is the eventual goal is implementing the cpu_alloc
>> functions which I think we've agreed has to be "growable".  This means
>> that
>> the addresses will need to be virtual to allow the same offsets for
>> all cpus.
>> The patchset I have uses 2Mb pages.  This "little" twist might figure
>> into the
>> implementation issues that are being discussed.
>>
> 
> No, since the *addresses* can be arbitrary.  The current issue is about
> *offsets.*
> 
>     -hpa

Ok, thanks for clearing that up.  I just didn't want us to drop the ball
trying to make that double play... ;-)

Cheers,
Mike
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