Something I've noticed in KDE, mainly when using the System Settings menu:
Sometimes (about 40% of the time), menus will be very laggy, while the rest of the time they are virtually instantaneous. And it's not totally random - it will go through periods of being consistently laggy and then consistently fast.
For example, when changing a setting in one of the System Settings menu tabs, and then changing to a different tab without saving the changes, sometimes the dialog box that asks whether you want to discard your changes or not will be extremely slow to appear i.e. take 3-4 seconds, while the rest of the time it's virtually instant.
Has anyone else noticed this / able to reproduce it / have a fix for it?