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

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Message-ID: <48779411.1080909@zytor.com>
Date:	Fri, 11 Jul 2008 13:10:41 -0400
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Christoph Lameter <cl@...ux-foundation.org>,
	Mike Travis <travis@....com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...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

Eric W. Biederman wrote:
>> x86_64 are small systems? For 64 bit use one would expect 4GB of memory.
> 
> Anything over 1G where 32bit runs out of lowmem starts to be a win.
> Plus sometimes it just doesn't make sense to use a 32bit kernel.
> 
> Expecting 4GB of real memory seems silly.

Especially since people set up VM instances small and then grow them. 
They can have *weird* CPU-to-RAM ratios; I have heard of 8 VCPUs and
24 MB of RAM in production.

	-hpa

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