High load when running VirtualBox

[Michael Stucki]

When running VirtualBox, the system load suddenly raises without stopping. When I kill compiz (which includes Unity), the load goes down again. If I don't kill it quick enough, the system locks up completely and I need to power off the machine.

I was searching very long for a solution because I thought it's a VirtualBox problem. I'm using the Oracle 4.2.12 package provided on http://www.virtualbox.org/, but I also tried using the stock Ubuntu package and even with an older VirtualBox version (4.1), but the problem still occured.

Before I had this problem, I was using Ubuntu 12.10 without any issues. When 13.04 came out, I decided to make a fresh installation and have this problem since then.

Description of the problem:
- I'm running Ubuntu 13.04 on an Asus Zenbook UX31A with 4 GB memory and 128 GB SSD.
- Before I start VirtualBox, I have already opened several programs: Chromium, Firefox, Skype are the biggest in terms of memory usage (I think the problem occured less often when VirtualBox was running alone, so maybe it's related to memory usage)
- When I start VirtualBox, the problem occurs sometimes during boot, but sometimes only after a a few minutes of uptime. Most of the time, it happened when the machine was idle and I was working in a different window.

Workarounds:
1) I can use Unity only when I run a background job which checks for the load and kills / replaces compiz & unity if the system load is too high.
2) I decided to install ubuntu-gnome-desktop and switch to GNOME for the time being. It uses compiz as well but without Unity, and the problem is completely gone! (That's why I'm pretty sure it must be a Unity issue...)

[Michael Stucki (mstucki)]

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!