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Date: Thu, 18 Jan 2007 21:01:41 +1100 (EST)
From: Bruce Evans <bde@zeta.org.au>
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Cc: Maxim Sobolev <sobomax@FreeBSD.org>, Ivan Voras <ivoras@fer.hr>,
	Attilio Rao <attilio@FreeBSD.org>, freebsd-current@FreeBSD.org,
	freebsd-arch@FreeBSD.org
Subject: Re: [PATCH] Mantaining turnstile aligned to 128 bytes in i386 CPUs
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On Wed, 17 Jan 2007, Suleiman Souhlal wrote:

> Bruce Evans wrote:
>> I haven't tried this, but have seen and partly worked sensitivity to
>> linear KVA maps not being physically (non)linear enough.  Some CPUs
>> and/or memory systems are remarkably sensitive to bank interleave.
>> FreeBSD's page coloring doesn't know anything about banks, ...
>
> About page coloring: Don't amd64 CPUs have virtually indexed, physically
> tagged caches? If so, wouldn't it make sense to turn off page coloring,
> since it's useless for virtually indexed caches (and probably hurts things
> a bit)?

I think superpages will soon turn off coloring.  Not sure if this is
right.  How is copying and zeroing a whole superpage at a time avoided?

IIRC, my benchmarks (and LMbench) show some small positive benefits for
page coloring on amd64.  I don't remember exactly what they are, just
that they are smaller than on AthlonXP.

Bruce