Comment 65 for bug 342923

As Tom pointed out, fixing the MTRR range does not require installation of the experimental kernel.

Also, the MTRR fix is (AFAIK) to improve EXA performance (by allowing DRI1 to correctly do write-combining), and you were clearly running UXA as per the log you posted. Also you need to remember that restarting X resets the MTRR ranges.

I'm working on a script to automate the process so that it can be easily included in xinit. (it extracts the base address and memory size and then does the appropriate echo)

As for glxgears, the only thing it indicates is how quickly the framebuffer can be refreshed (as there is no real drawing going on), it doesn't say anything about real-world performance, unless DRI is simply not working and glxgears runs with a framerate below your screen refresh rate. Running OpenGL games or looking at the framerate indicator in KWin are much more accurate measures of real-world performance.