  The Gemini Planet Imager instrument's adaptive optics (AO) subsystem was
designed specifically to facilitate high-contrast imaging. It features several
new technologies, including computationally efficient wavefront reconstruction
with the Fourier transform, modal gain optimization every 8 seconds, and the
spatially filtered wavefront sensor. It also uses a Linear-Quadratic-Gaussian
(LQG) controller (aka Kalman filter) for both pointing and focus. We present
on-sky performance results from verification and commissioning runs from
December 2013 through May 2014. The efficient reconstruction and modal gain
optimization are working as designed. The LQG controllers effectively notch out
vibrations. The spatial filter can remove aliases, but we typically use it
oversized by about 60% due to stability problems.
