问题的原因是 Compiz/Unity 的 bug造成的。
可以按如下方法更新Compiz/Unity：
sudo add-apt-repository ppa:townsend/compiz-nvidia-refresh-test
PPA description
This PPA adds the patch to Compiz to (hopefully) fix the screen refresh issue often seen on Nvidia based graphics.
Adding this PPA to your system
You can update your system with unsupported packages from this untrusted PPA by adding ppa:townsend/compiz-nvidia-refresh-test to your system's Software Sources.
This PPA can be added to your system manually by copying the lines below and adding them to your system's software sources.
deb http://ppa.launchpad.net/townsend/compiz-nvidia-refresh-test/ubuntu trusty main
deb-src http://ppa.launchpad.net/townsend/compiz-nvidia-refresh-test/ubuntu trusty main
Signing key:
1024R/D380BEEB (What is this?)
Fingerprint:
968308DEDD6F8004F99C355A7F8BD479D380BEEB
Compiz Nvidia refresh test : Christopher Townsend：https://launchpad.net/~townsend/+archive/ubuntu/compiz-nvidia-refresh-test