after logoff/login the plasmashell now use a normal CPU %age (0.3%-0.9% when no activity up to 25% when starting the browser but return to low %age after load). I don’t see why the preceding session ended which such high CPU usage by plasmashell.
I have the feeling that sometime plasmashell is unable to stop some child processes and then the CPU usage grows and remains high.
Journalctl shows only one strange error
hpprol2 systemd-coredump: Resource limits disable core dumping for process 3668 (kactivitymanage).
hpprol2 systemd-coredump: Process 3668 (kactivitymanage) of user 1000 dumped core.
As far as I see this occurs when terminating a session (logoff)