Re: [RFC] Hacky MTRR support

[Colin D Bennett <colin@gibibit.com>]

On Fri, 25 Jun 2010 09:58:34 +0100
Colin Watson <cjwatson@ubuntu.com> wrote:

> I recently posted ("Subject: [PATCH] Optimise memset on i386" -
> sorry, I don't seem to have a route to lists.gnu.org at the moment so
> I can't post an archive link) about optimising GRUB's video
> initialisation, and hinted that it might be possible to do better by
> implementing MTRRs as well in order to allow the system to combine
> writes to video memory rather than taking a cache stall for every
> single write.  I can report that, at least on the hardware I was
> using, it does make a significant difference: filling the screen with
> solid colour now takes 10 milliseconds rather than 160!  This ended
> up shaving about a second off the boot time of the project I'm
> working on.

In addition to the improved startup speed, I see the potential for a
huge increase in graphical menu responsiveness if caching is enabled.
Would framebuffer draw and image blitting performance be improved by
using write-combining with MTRRs?

Regards,
Colin