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SubjectRe: Performance issue in 2.5.32+
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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