Ubuntu 20.04 gnome-shell continual 20% CPU usage

Just in case anybody has a similar issue, I had CPU usage of 80% consistently from GNOME Shell and I switched the various extensions off for testing, on version 20.04.

It turned out I had the performance monitor in the top right hand side bar (system load monitor) - once that was quit, everything was back to normal. If anybody has any suggestions how to diagnose why I'm happy to test.

This seems to be a big issue, I don't have any extensions loaded and it takes 40% CPU on idle.

However I disabled Wayland and it went to less than 1%.

I disabled it using this: https://askubuntu.com/a/968265/78252

If you wish to do it permanently, edit

/etc/gdm3/custom.conf and uncomment the line

#WaylandEnable=false by removing the # in front.

Save the file and then on reboot you will never see the cog asking for which session to use.