Ubuntu 10.04: Fixing mtrr errors

Ah, so many things, so little time to write about them. I'm going to handle my Ubuntu 10.04 programs piecemeal, and in the order that I have time to write about them. So this one isn't the biggest problem, but I've got all the data available here, and it's a quick fix, so here goes:

I was looking at /var/log/messages to try to figure out why my wife's account logged itself off last night (never did find out), when I saw the message

MTRR allocation failed. Graphics performance may suffer.

Googled it, found this fix, which is to add the kernel boot options:

enable_mtrr_cleanup mtrr_spare_reg_nr=1

to the grub command line.

Uh, OK, how do I do that?

In the Good Old Days there was a file, /boot/grub/menu.lst, which had all the information you needed to get your computer started, including booting up and loading the kernel with the desired options. The problem was that this got rewritten every time you did a kernel update. There were some sections of the file that were supposed to be saved, but that required the update program to remember to save them.

Just to make sure the programmer didn't forget those kind of things, all of the user-specified options were moved to the file /etc/default/grub, and menu.lst has become grub.cfg, which is generated from /etc/default/grub by running update-grub.

Got that? Uh, so you just ... Oh, never mind.

Here's the fix for the mtrr problem:

1. Run
   $ sudo vi /etc/default/grub
   to edit the grub configuration file.
2. Look for the line
   GRUB_CMDLINE_LINUX=""
   and change it to
   GRUB_CMDLINE_LINUX="enable_mtrr_cleanup mtrr_spare_reg_nr=1"
3. Save and exit
4. Run
   $ sudo update-grub
5. Check /boot/grub/grub.cfg to be sure the changes are in there
6. Reboot
7. Check /var/log/messages to be sure that the mtrr message has disappeared.

And, of course, I noticed a fantastic improvement in graphic performance — which means none, actually. But hey! I got rid of the error message.