Comment 32 for bug 270377

This problem has been much discussed in the nvidia user support forums. It appears to only/mostly arise when Compiz is in use. The problem is caused by an Nvidia feature called "powermizer" that pushes the video card into low performance mode. Some people say some changes in xorg.conf help, but I tried them all and none mattered. On my Lenovo T61, I found that an option for the nvidia kernel module does help. You can force powermizer into a higher rate with a kernel module option. Here is the content of the option that fixes it for me.

$ cat /etc/modprobe.d/nvidia
options nvidia NVreg_RegistryDwords="PerfLevelSrc=0x2222"
options nvidia NVreg_Mobile=1

The Nvidia techs are aware of this and they have a beta driver that helps, but at the moment it randomly crashes the system. You win some, you lose some.

pj