linux-kernel - Re: [PATCH] move the kernel to 16MB for NUMA-Q

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Message-ID: <466D8E02.3070403@gmail.com>
Date:	Mon, 11 Jun 2007 20:01:38 +0200
From:	Rene Herman <rene.herman@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	Dave Jones <davej@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Whitcroft <apw@...dowen.org>,
	Steve Fox <drfickle@...ibm.com>, Mel Gorman <mel@....ul.ie>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] move the kernel to 16MB for NUMA-Q

On 06/11/2007 07:58 PM, H. Peter Anvin wrote:

> Rene Herman wrote:
>> Aligning the kernel image on 4M could gain an additional TLB entry if
>> the kernel image would fit in one (4M aligned) hugepage, but not in the
>> 3M that's left after loading the kernel at 1M physical. And that stuff
>> about the MTRRs...
>>
> 
> Yup.  Most CPUs won't actually use a largepage for the kernel if it's
> below 4 MB (2 MB with PAE, so that's what x86-64 uses.)

Oh, thanks, that's interesting. Had no idea. In those cases it would seem to 
at least potentially be a serious performance issue.

Rene.

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