Comment # 4 on bug 79842 from Grigori Goronzy

Probably related to this:

http://cgit.freedesktop.org/mesa/mesa/commit/?h=10.1&id=1ba2298131924daf34b4504ba748a782c5189f48

Anisotropic filtering was broken in radeonsi, and that fixed it. Anisotropic
filtering has some overhead, which explains the slightly reduced performance.

This patch was applied to 10.1 and 10.2 branches as well as master.