I find starting KDE rather painfull, because it is such a slow operation. There is a thread here suggesting to not start plasma-desktop, and then do that manually, but this is 2012! It is also suggested to not run /etc/xdg/autostart/pulseaudio-kde.desktop.

But even after being done, I have some problems:
* plasma-desktop keeps using about 30-50% CPU infinitely, untill I restart it. May have to do with the eventlist plasmoid, which seems to be VERY slow at loading.
* kio_thumbnail seems to be running for a LOOOOOOOOONNNNNNGGGG time after starting is finished. Why does it do that? Is there a way to see what it does? (enabling kio_thumbnail debugging does not show anything at all.)

After starting, it is unfortunately nessecary to stop KDE at some point too - I do that rarely, but once in a while I reboot after updating the system. When doing that, KDE first just sits there doing nothing at all (appearently) for 10-20 secs, then sloooooooooooowwwwly it starts shutting down applications. I do not understand why that takes so long time - pressing ctrl + q to quit any application is usually very fast. Of course each app have an extra function to save session data, but that is so little it should not matter, most apps saves all the required data anyways. So something must be wrong somewhere!

I use "restore previous session", which probably affects both startup and shutdown, but I like that functionality, and I do not understand why it should cause so much waste of time to do that.

Any tips for improving performance, or for debugging KDE startup and shutdown would be appreciated!

You will find that e4rat will speed things up beyond recognition