Re: Mmap device performance

Alan Cox (alan@lxorguk.ukuu.org.uk)
Thu, 11 Dec 1997 11:20:33 +0000 (GMT)

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> On the PPro and PII boxes the performance is roughly half what it is
> under Windows. Since the application is identical, and the interface to
> the card is simply writing to a memory mapped region so it seems that
> the degradation must be happening somewhere in the kernel layers. I'm
> currently mapping the region shared with read/write access.

You need to reconfigure the MTRR's on the processors as well. The Windows
driver will be setting the card to be write gathering. See the Intel
Pentium Pro programming manuals

Alan

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