As requested in the upstream bug report https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/6137, I hereby file the downstream issue:
I am experiencing high cpu usage of gnome-shell in situations where I would not expect it, leading to my fans running more often and wasting my battery on my Dell XPS 13 9310 2-in1.
The problem can be seen in action here: https://www.youtube.com/watch?v=Y9o7a7BGPE4
See also the upstream report for syscap recordings of such situations.
I think there might be a correlation with firefox being opened on another workspace (but no video or any other playback happening). At least everytime I notice that my an comes on for no reason and I fire up top to see gnome shell consuming too much cpu, when I kill all my firefox windows gnome shell cpu usage goes down as well, but that could be pure coincidence.
At least I can safely rule out the triple buffering downstream ubuntu mutter patch, since I recompiled mutter without the patch and it does not really change the problem much.
Thanks for the bug report. In your video I can see two causes that are not really bugs:
* Firefox using CPU at the same time as gnome-shell means it is Firefox causing the persistent CPU usage in gnome-shell. Make sure Firefox isn't displaying animations like web ads. Even if that doesn't look like the problem, it's still Firefox's fault if the problem is correlated with that app running.
* Triggering the window spread animation causes even higher gnome-shell CPU usage. This is normal and not a bug. Although we welcome patches to make it more efficient.
Suggested workaround: Make Firefox render more efficiently by adding MOZ_ENABLE_