Re: 2.0.x SMP performances compared to 2.1.x

David Wragg (dpw@doc.ic.ac.uk)
30 Aug 1998 16:56:24 +0000

Claude Gamache <cgamache@cae.ca> writes:
> In the 2.1.117 kernel, we have the mtrr (memory type range register)
> support. When we activated the mtrr for the video card at the prompt
> (by following the instructions of the mtrr documentation), things got
> even worse, performances dropped by about 50% ! According to the mtrr
> documentation we should have seen improvements. We also tried mtrr
> with a dual IBM Intellistation Z Pro equipped with 2 Pentium Pro 200
> MHz 512 kb cache running kernel 2.1.115 and, again, we got a
> performance degradation when we enabled mtrr.

Bizarre. I can't think how the MTRR stuff could affect the
non-graphical performance to any significant extent (in either
direction), unless it was configured in ways that shouldn't be
possible with the current MTRR driver.

Do you get a performance degradation between a kernel built without
CONFIG_MTRR and one with, or does it only appear after you write to
/proc/mtrr to configure it for your video card?

Could you post the output of "cat /proc/mtrr", and the output of
"scanpci" or "lspci", please.

--
Dave Wragg




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