The above numbers where using the modesetting driver since I was trying to keep
as much the same between radeon and amdgpu.  I get similar behavior from amdgpu
though.

Both radeon and amdgpu built from commit:
   https://cgit.freedesktop.org/~agd5f/linux/
   drm-next-4.9-wip

   commit 25114c509cc39b387aa358a86fa48c855266a6fe
   Author: Alex Deucher <alexander.deucher@amd.com>
   Date:   Wed Sep 14 14:15:34 2016 -0400

       drm/radeon/atif: Send a hotplug event when we get dgpu display request

Mesa:
   commit 6b0ba02cae1526d6e6671a9ff620fd3bd7d4d032

llvm:
   commit 338f974b6e4f5d5d004d36d0d446289280d0c372

drm:
   commit 2d00869599a1c853238401a38a334c3bc8673343