$ DRI_PRIME=1 glxinfo | grep "OpenGL renderer"
OpenGL renderer string: Gallium 0.4 on AMD PITCAIRN (DRM 2.49.0 / 4.10.0-34-lowlatency, LLVM 4.0.0)

$ glxinfo | grep "OpenGL renderer"
OpenGL renderer string: Mesa DRI Intel(R) Ivybridge Mobile