High CPU when on another user's desktop

[mannheim]

Binary package hint: cairo-clock

Steps to reproduce:

1. Log in as "User A" with gnome and compiz.
2. Launch cairo-clock.
3. Do a "Switch User" and start a session as "User B".
4. As "User B", run the "top" command in a terminal.

Actual Results: The compiz process belonging to "User A" is using 67% of one core on my machine.
Expected Results: The compiz process belonging to "User A" is using very little CPU.

This is 100% reproducible on my setup, with Ubuntu 8.04 and cairo-clock 0.3.3-2 from the repositories. It also occured with Ubuntu 7.10. If you kill the cairo-clock process belonging to "User A" then the CPU usage of the compiz process drops to negligible size. I don't know if I should call this is a bug with cairo-clock, or compiz, or what. Certainly, the end result is that cairo-clock cannot really be used in an environment where user-switching is common.

[mannheim (kronheim)]

I changed the affected package from cairo-clock to compiz, because I think that I get the same sort of behavior in other settings. For example, run Firefox and open a flash movie; then switch users.

Instead of switching users, you can also get the same behavior by doing Ctl-Alt-F1 to get to a new tty. Running top in the new tty then shows compiz using a large share of CPU, if there is an application running such as cairo-clock or a flash video in compiz.

[Mackenzie Morgan (maco.m)]

What version of Compiz are you using?

[mannheim (kronheim)]

I am using the version that ships in the Ubuntu hardy repostories: at present, compiz-core is version 0.7.4-0ubuntu7.

[Hannes Ovrén (kigurai)]

I also experience that compiz.real is using the CPU intensly when using the gnome-fast-user-switching-applet.
I login as user A (which uses compiz) and then switch to user B. User B has no problems. Then I switch back to user A again and after unlocking the screen the desktop is almost unusable.
Doing ALT-F2 and "metacity --replace" is the only way I've found to bring back my desktop without logging out and back in again.

[Robert Ancell (robert-ancell)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. The issue that you reported is one that should be reproducible with the live environment of the Desktop CD of the development release - Jaunty Jackalope. It would help us greatly if you could test with it so we can work on getting it fixed in the next release of Ubuntu. You can find out more about the development release at http://www.ubuntu.com/testing/. Thanks again and we appreciate your help.

[Travis Watkins (amaranth)]

We're closing this bug since it is has been some time with no response from the original reporter. However, if the issue still exists please feel free to reopen with the requested information. Also, if you could, please test against the latest development version of Ubuntu, since this confirms the bug is one we may be able to pass upstream for help.