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

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Date:	Thu, 10 Jul 2008 17:55:35 -0700
From:	Mike Travis <travis@....com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Ingo Molnar <mingo@...e.hu>,
	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:
> Jeremy Fitzhardinge wrote:
>>
>> Percpu on i386 hasn't been a point of discussion.  It works fine, and
>> has been working fine for a long time.  The same mechanism would work
>> fine on x86-64.  Its only "issue" is that it doesn't support the
>> broken gcc abi for stack-protector.
>>
>> The problem is all zero-based percpu on x86-64.
>>
> 
> Well, x86-64 has *two* issues: limited range of offsets (regardless of
> if we do RIP-relative or not), and the stack-protector ABI.
> 
> I'm still trying to reproduce Mike's setup, but I suspect it can be
> switched to RIP-relative for the fixed-offset (static) stuff; for the
> dynamic stuff it's all via pointers anyway so the offsets don't matter.
> 
>     -hpa

I'm rebuilding my tip tree now, that should bring it up to date.  I'll
repost patches #1 to (currently) #4  shortly.

I'm looking at some code that does not have patches I sent in like 4 to 5
months ago (acpi/NR_CPUS related changes).

Thanks,
Mike
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