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

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Date:	Thu, 10 Jul 2008 17:58:43 -0700
From:	Mike Travis <travis@....com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Christoph Lameter <cl@...ux-foundation.org>,
	Jeremy Fitzhardinge <jeremy@...p.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:
> Mike Travis wrote:
>>
>> Hmm, that might be the way to go.... At boot up time determine the
>> size of the system in terms of cpu count and memory available and
>> attempt to do the right thing, with startup options to override the
>> internal choices... ?
>>
>> (Surely a system that has a "gazillion ip tunnels" could modify it's
>> kernel start options... ;-)
>>
>> Unfortunately, we can't use a MODULE to support different options unless
>> we change how the kernel starts up (would need to mount the root fs
>> before starting secondary cpus.)
>>
> 
> Using a module doesn't make any sense anyway.  This is more what the
> kernel command line is for.
> 
>     -hpa


I was thinking that supporting virtual percpu addresses would take a fair
amount of code that, if living in a MODULE, wouldn't impact small systems.
But it seems to be not worth the effort... ;-)

Thanks,
Mike
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