Hi, I'm experiencing bad alt-tab performance with nvidia. It's just the switching windows performance; other desktop effects works great (minimize animation, desktop grid, etc). It seems like kwin is having trouble painting the windows, since when I put my mouse on the taskbar for "window previews," kwin CPU jumps a lot.

I'm running:
Arch Linux
Xorg 1.9.0
KDE 4.5.2
GeForce 6150
nvidia 260.19.12

Tried different Desktop Themes (Oxygen, Air etc) but didn't help. Environment variables such as LIBGL_ALWAYS_INDIRECT or QT_GRAPHICSSYSTEM didn't work either.

Sorry, never mind. Blacklisting Lanczos seems to have helped.

viewtopic.php?f=111&t=90755#p172767