linux-kernel - Re: why does the macro "ZERO

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Message-ID: <46687598.2040701@zytor.com>
Date:	Thu, 07 Jun 2007 14:16:08 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	William Lee Irwin III <wli@...omorphy.com>
CC:	"Robert P. J. Day" <rpjday@...dspring.com>,
	Satyam Sharma <satyam.sharma@...il.com>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ralf Baechle <ralf@...ux-mips.org>
Subject: Re: why does the macro "ZERO_PAGE" take an argument?

William Lee Irwin III wrote:
> Robert P. J. Day wrote:
>>> although it's not clear where in the source tree are the invocations
>>> that would actually make a difference to a MIPS system, which is why
>>> i've CC'ed ralf on this.  i'm sure he can clear this up. :-)
> 
> On Thu, Jun 07, 2007 at 10:32:29AM -0700, H. Peter Anvin wrote:
>> x86 could also benefit from coloured zeropages.  In fact, I thought it
>> already had them (K8 wants as many as 8.)
> 
> How would one demonstrate the beneficial effect of such?

Dean Gaudet at Transmeta did some benchmarking using SPEC.  If I recall
his numbers correctly (this is from memory, mind you) on Transmeta
Efficeon, which has 2-way virtual cache tagging with hardware recovery,
zeropage coloring was a 1.5% performance improvement.

	-hpa

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