Re: why does the macro "ZERO_PAGE" take an argument?

From: Nick Piggin
Date: Mon Jun 11 2007 - 22:18:20 EST

H. Peter Anvin wrote:
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.

I'm surprised that the benchmark made such use of zero pages so as to
be worthwhile. I'm sitting on a patch which removes the zero page from
the page fault fastpath completely which I'd like to try out in -mm...

SUSE Labs, Novell Inc.
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