Not OP, but plasmashell, activitymanagerd, recently krunner. The first two because I have a sshfs mount, the latter only recently for no good reason.

>Not OP, but plasmashell, activitymanagerd, recently krunner. The first two because I have a sshfs mount, the latter only recently for no good reason.

I don't doubt you, I never had performance issue with my KDE though I always run LTS Kubuntu. I am wondering why plasma or activity monitor would have issues with your filesystem.

My guess is that they query a service that does file operations for no good reason, and then busy wait for it.