Okay, so Im currently using Mandriva 2009 Beta, which ships with KDE 4.1 final. I have an Nvidia 8800GTS video card, and was having some issues with it. After a *lot* of googling (neat how thats a verb now, isnt it?) I think I have finally gotten my issues straightened out. After doing what Im about to explain here, windows render fairly quickly and smoothly, and I've noticed other performance increases related to video and plasma. This should work for any distro, for anyone using an Nvidia card newer than the 7000 series.
Step 1: Install the latest Nvidia driver, even if its beta. Im using 177.67. I suppose it depends on your distro, but I like the binary installer from Nvidia over Mandriva's RPMs. I recommend you uninstall any packaged driver from your distro and do the same.
Link to Nvidia beta driver 177.67
Step 2: Put the following command in your ~/.kderc or ~/.xinitrc/ ~/.gnomerc, etc.
nvidia-settings -a InitialPixmapPlacement=2 -a GlyphCache=1
My /etc/X11/xinit/xinitrc file looks like:
exec /etc/X11/Xsession $*
exec nvidia-settings -a GlyphCache=1
exec nvidia-settings -a InitialPixmapPlacement=2
Setting InitialPixmapPlacement to a value of 1 or 3 may improve performance on some cards.
Step 3: Add the following options to your xorg.conf file.
Option "PixmapCacheSize" "1000000"
Option "AllowSHMPixmaps" "0"
Option "RenderAccel" "true"
Option "UseEvents" "false"
Option "TripleBuffer" "1"
Option "DamageEvents" "1"
Option "BackingStore" "1"
Option "OnDemandVBlankInterrupts" "true"
Regarding PixmapCacheSize, this option reserves a chunk of your GPU's video memory for fast pixmap allocation and greatly improves performance of any X application heavily relying on pixmap allocation. The PixmapCache size is measured in pixels; a pixel of PixmapCache uses a little more than 5 bytes of video memory, meaning a PixmapCacheSize of 1,000,000 will reserve a little under 5MB of video memory for pixmap allocation. Feel free to increase this size to get better performance, taking into account the amount of memory on your graphics card and the fact that this memory will be unavailable for OpenGL texture allocation. Since I have 640Mb of Vram, I used a value of 2000000.
Step 4: Log out and then restart X.
Step 5: Pray
Step 6: Log back in
Hopefully once this is all done, you notice a performance increase with window resizing and such. If you don't, try changing some of those values with pixmapcachesize and initialpixmapplacement.
Most of this info is available if you google around, but I didn't see any posts regarding this issue on LQ. I Hope it helps some others out there.