Disable vertical refresh sync using glxgears

When you run glxgears sometimes by default your fps get crapped about 60fps, which is the same as your vertical refresh rate of your monitor! (60Hz -> 60fps)
  To disable it you can set the environment variable vblank_mode to zero, and run again the glxgears:

$ export vblank_mode=0 
$ glxgears

Then you'll see glxgears running at full fps possible!

My system running glxgears on vblank_mode=0