Sign up ×
Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

I have been running my Ubuntu Linux Machine recently on powerful hardware (much more powerful than my last machine at any rate) and I have noticed that after some time all of a sudden X11 starts to behave terribly and eats a (fluxuating) average of 50% CPU usage of one of my cores. I have four cores and my computer still runs but when that begins everything from keyboard input to playing movies begins to lag and there is not way that I can get the terrible performance to stop without rebooting my computer.

The exact specifications of my computer are:

Linux ShhnapDesk 2.6.38-10-generic #46-Ubuntu SMP Tue Jun 28 15:07:17 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux

I am running XMonad and XMobar through my .XSession file. I like them as window managers.

I have searched around and I do not seem to be alone in this problem. Many people seem to have encountered it over the years as is listed here:

I also looked into the Ubuntu X Troubleshooting guide and found this:

X CPU or memory load is high, making system laggy or freeze up. This usually indicates a client application has lost its marbles.

So if an X application has lost its Marbles then which X application is it? Well I reasoned that if the problem started and I shut down every X application then when I shut down the problem application then the problem should go away. I tried that and shut down every X application (or atleast I thought I did) and the problem still remained. Though I did not shut down XMonad because it is my window manager. I guess that it could be the problem but I would not expect it to be. Especially since it did not cause these issues on my last machine.

So my question is: what is happening and how do I fix it so that X11 stops going haywire and eating all of my CPU and behaving like a slug? Thankyou for any and all responses, I suspect that I am going to need alot of help though if I have missed out on any information then I can give you any more that you need to help me debug the problem.

share|improve this question
I have the same problem: about ones in an hour X11 is working hard for about a minute (Kubuntu 11.04). – Adobe Aug 27 '11 at 13:22
Adobe: You make it sound like after an hour it goes back to normal. I would not consider that a huge problem, just an annoyance. With mine, once it starts lagging it never stops till I reboot the computer or completely restart X11 and gdm. Yuck. – Robert Massaioli Oct 18 '11 at 2:08
Robert Massaioli: sounds like a serious problem. Seems to me to be a hardware one. Mine goes back to normal in a minute. But this is repeated in an hour. – Adobe Oct 18 '11 at 7:05
Can you post: OS version, driver version, graphics card? – Not a Name Nov 21 '11 at 22:17

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.