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

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Date:	Wed, 09 Jul 2008 17:24:05 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, Mike Travis <travis@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jack Steiner <steiner@....com>, linux-kernel@...r.kernel.org,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: [RFC 00/15] x86_64: Optimize percpu accesses

H. Peter Anvin wrote:
> Eric W. Biederman wrote:
>> Jeremy Fitzhardinge <jeremy@...p.org> writes:
>>
>>>> Which means that my idea of using the technique we use on x86_32 
>>>> will not
>>> work.
>>>
>>> No, the compiler memory model we use guarantees that everything will 
>>> be within
>>> 2G of each other.  The linker will spew loudly if that's not the case.
>>
>> The per cpu area is at least theoretically dynamically allocated.  
>> And we
>> really want to put it in cpu local memory.    Which means on any 
>> reasonable
>> NUMA machine the per cpu areas should be all over the box.
>>
>> So there is no guarantee that with an arbitrary 64bit address in %gs 
>> of anything.
>>
>
> That doesn't matter in the slightest.

Creepy, get out of my brain.

    J
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