By default, Desktop Effects or Desktop Compositing is enabled by default.
I have a VM in VirtualBox running KDE. When these desktop effects are enabled, everything is horribly slow.
This is how you disable them:
- Open System Settings -> Display and Monitor -> Compositor
- Uncheck “Enable compositor on startup”
- Open System Settings -> Shortcuts -> Global Shortcuts -> KWin
- remotve the SUspend Compositing shortcut
Restart KDE or the VM.