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Date: Tue, 10 Sep 2002 02:06:04 +1000 (EST)
From: James Morris <jmorris@intercode.com.au>
To: Linus Torvalds <torvalds@transmeta.com>
cc: linux-kernel@vger.kernel.org
Subject: Re: Performance issue in 2.5.32+
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On Sun, 8 Sep 2002, Linus Torvalds wrote:

> I don't really see anythign very suspicious in the 31->32 changelogs. 
> Somebody else already mentioned TLS etc, but that shouldn't really be 
> noticeable...

I've now tracked the problem to the introduction of the new mtrr code, and
backing it out for 2.5.32 restores original performance.  From what I can 
tell, the new code is not handling a bios/hardware bug that the old code 
was.

The old mtrr code says this during bootup:
 mtrr: your CPUs had inconsistent fixed MTRR settings
 mtrr: your CPUs had inconsistent variable MTRR settings
 mtrr: probably your BIOS does not setup all CPUs

While the new code just says:
 mtrr: SMP support incomplete for this vendor

The peformance hit is basically the same as when the old mtrr code is 
disabled.  I'll have a poke around and see if I can find out why the new 
mtrr code isn't handling the problem.


- James
-- 
James Morris
<jmorris@intercode.com.au>


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