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

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Message-ID: <48764E8A.5010400@zytor.com>
Date:	Thu, 10 Jul 2008 14:01:46 -0400
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Mike Travis <travis@....com>
CC:	Jeremy Fitzhardinge <jeremy@...p.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	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

Mike Travis wrote:
> 
> The discussion that followed was very emphatic that the size of the space should
> not be fixed, but instead be dynamically growable.  Since the offset needs to be
> fixed for each cpu, then virtual (I think) is the only way to go.  The use of a
> 2MB page just conserves map entries.  (Of course, if we just reserved 2MB in the
> first place it might not need to be virtual...?  But the concern was for systems
> with hundreds of (say) network interfaces using even more than 2MB.)
> 

I'm much more concerned about wasting an average of 1 MB of memory per CPU.

	-hpa
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