CPU pegs at 100% with 3D apps

Question

I have a GeForce 8800 GTS, and running the proprietary drivers. When I run Urban Terror (FPS game), I get a lot of lag. I did some tests with glxgears, and saw that my both CPU cores are pegging at 100%, and the 3D app I use is the one that is pegging according to top. I am not using an xorg.conf, just letting X set itself. Here is my xorg.log: http://pastie.org/2957867
Any suggestions on what to look for or try?

Answer 1

Good to hear that something changed although I am unsure what was caused the CPU load.
If VSync isn't enabled, then any OpenGL apps (unless explicitly configured to do otherwise) will try to push out as many frames as they can at a time.  This causes both high GPU load (because it has to render all the extra frames that you'll never see, since the display can only refresh so fast), and high CPU load (since it has to push out all those extra GL commands to the GPU).  Forcing VSync system-wide will force all OpenGL apps to only update their display when the monitor has finished refreshing and is about to start on a new image (the VBlank interval), effectively capping the frame rate to the refresh rate of your monitor, though unless you're using triple buffering, this can also have some nasty side-effects as well; see here and here for more details if you're interested.