On Mon, Aug 21, 2000, David Mosberger <davidm@hpl.hp.com> wrote:
>   Mark> 2) No mechanism for the X-server to write combine memory and
>   Mark> no discussions on adding this to Linux as far as I can tell.
>   Mark> There needs to be a new flag to open() or mmap().  There
>   Mark> aren't any MTRRs.
> 
> I submitted a patch for the tdfx DRM module to map non-AGP stuff as
> write-combined (actually, I'm not 100% sure this is the right thing to
> do here; a DRM expert may want to double check this; it does seem to
> work fine on my machine).  See the latest Linux kernel patch.
> 
> Linus already agreed that it would be OK to add additional mmap()
> flags to indicate the memory attribute (normal vs. write-combine
> vs. uncached).  Walt says a patch to do this was developed as part of
> the XFree86 4.0 work at VA and promised to send me a patch.  I don't
> think I have received such a patch, but I'd be happy to merge it
> in. ;-)

Now that we have a stable platform, we were able to test the patch and
confirm the patch wasn't causing the stability problems we were seeing.

This gets a 3 times speed improvement over non write combined memory in
the tests Mark performed.

The patch is against 2.4.0-test9-ia64-001004

JE