Early Benchmarks Of The Linux 4.9 DRM-Next Radeon/AMDGPU Drivers
Not much of a difference with Counter-Strike: Global Offensive or Dota 2 (OpenGL) with the new kernel code being queued for Linux 4.9. It does look like the performance may be a tiny bit slower, but the margins are too close to call at this time.
The Metro Last Light Redux performance was the same except for the Radeon R9 285 that regressed with the DRM-Next run.