Here's an update. After a few days of running GNOME, the same problem occured again. Apparently the problem is not caused by Unity!
Meanwhile, I found some lines in the logfile: May 17 11:47:48 zenbook rtkit-daemon[1691]: The canary thread is apparently starving. Taking action. May 17 11:47:54 zenbook rtkit-daemon[1691]: Demoting known real-time threads. May 17 11:47:59 zenbook rtkit-daemon[1691]: Successfully demoted thread 2257 of process 2250 (n/a). May 17 11:48:16 zenbook rtkit-daemon[1691]: Successfully demoted thread 2256 of process 2250 (n/a). May 17 11:48:37 zenbook rtkit-daemon[1691]: Successfully demoted thread 2255 of process 2250 (n/a). May 17 11:48:45 zenbook rtkit-daemon[1691]: Successfully demoted thread 2254 of process 2250 (n/a). May 17 11:48:55 zenbook rtkit-daemon[1691]: Successfully demoted thread 2250 of process 2250 (n/a). May 17 11:49:02 zenbook rtkit-daemon[1691]: Demoted 5 threads. May 17 11:49:12 zenbook rtkit-daemon[1691]: The canary thread is apparently starving. Taking action. May 17 11:49:16 zenbook rtkit-daemon[1691]: Demoting known real-time threads. May 17 11:49:20 zenbook rtkit-daemon[1691]: Successfully demoted thread 2257 of process 2250 (n/a). May 17 11:49:29 zenbook rtkit-daemon[1691]: Successfully demoted thread 2256 of process 2250 (n/a). May 17 11:49:52 zenbook rtkit-daemon[1691]: Successfully demoted thread 2255 of process 2250 (n/a). May 17 11:50:22 zenbook rtkit-daemon[1691]: Successfully demoted thread 2254 of process 2250 (n/a). May 17 11:50:28 zenbook rtkit-daemon[1691]: Successfully demoted thread 2250 of process 2250 (n/a). May 17 11:50:39 zenbook rtkit-daemon[1691]: Demoted 5 threads. May 17 11:50:47 zenbook rtkit-daemon[1691]: The canary thread is apparently starving. Taking action. May 17 11:50:55 zenbook rtkit-daemon[1691]: Demoting known real-time threads. May 17 11:51:02 zenbook rtkit-daemon[1691]: Successfully demoted thread 2257 of process 2250 (n/a). May 17 11:51:07 zenbook rtkit-daemon[1691]: Successfully demoted thread 2256 of process 2250 (n/a). May 17 11:51:13 zenbook rtkit-daemon[1691]: Successfully demoted thread 2255 of process 2250 (n/a). May 17 11:51:32 zenbook rtkit-daemon[1691]: Successfully demoted thread 2254 of process 2250 (n/a). May 17 11:52:05 zenbook rtkit-daemon[1691]: Successfully demoted thread 2250 of process 2250 (n/a). Therefore I tried to disable rtkit-daemon (sudo rtkitctl --exit) and since then the system runs fine. Not sure yet, but I believe the problem is caused by rtkit, not unity! -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1180548 Title: High load when running VirtualBox To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/unity/+bug/1180548/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs