|Before making any changes to your system, please read everything carefully and try to understand what you are doing. If you're modifying any files on your system, keep copies of the unmodified version and be sure you can revert to those old version - even if your Xserver is not starting any longer.|
|Some of the changes mentioned below are said to increase the temperature of your GPU. In any case, monitor your graphic card to make sure it isn't getting too hot!|
Several popular graphics cards out there - especiall NVIDIA ones - exhibit performance problems with KDE4. These performance hits mostly concern Plasma - the KDE4 desktop - and KWin - the KDE window-manager. Generally speaking this isn't due to KDE4 being unoptimized but a problem with the cards' graphics drivers. This page encompasses certain problems that might arise and how to get rid of them.
Attributes set using the nvidia-settings utility aren't permanently saved. Thus you have to set them every time you restart your Xserver. This can be done conveniently by adding the lines to set the features to your ~/.xinitrc.
KDE4's systemsettings allows you to tweak some kwin settings as well. You can find the settings in Desktop -> Desktop Effects -> Advanced Options. Depending on your card either OpenGL or XRender might work better. For OpenGL changing the OpenGL mode might change performance as well. Please bear in mind that changing some of the tweaks mentioned below might force you to change your settings.
If for some reason your Xserver hangs after hitting the Apply button on the dialog and your settings get reverted because you can't confirm your changes in time, try again. Usually it will be faster on one of the subsequent tries. If it doesn't you can still change your settings in ~/.kde4/share/config/kwinrc.
This section summarizes several symptoms you might encounter and tries to explain possible causes.
$ XLIB_SKIP_ARGB_VISUALS=1 konsoleon the command-line and try to resize the new konsole window (setting the environment variable XLIB_SKIP_ARGB_VISUALS turns off ARGB visuals). If it resizes without problems, then this is certainly one of the problems you're facing.
Section "Device" ... Option "BackingStore" "true" ... EndSection "Device"This works for some (eg. konsole) but unfortunately not all windows.
$ nvidia-settings -a InitialPixmapPlacement=2This works for some (but unfortunately not all) NVIDIA cards.
$ nvidia-settings -a InitialPixmapPlacement=2 -a GlyphCache=1This works for some (but unfortunately not all) NVIDIA cards. Some cards reportedly work better using InitialPixmapPlacement=1 (or maybe even 3)