For those curious whether the Linux 4.6 kernel is bringing any noticeable performance improvements to the AMDGPU and Radeon DRM drivers over Linux 4.5, here are some benchmarks in conjunction with using Mesa 11.3-devel built against LLVM 3.8.
If you aren't yet familiar with the changes of this upcoming kernel release, see our Linux 4.6 feature overview. Within the Radeon/AMDGPU scope, there is now AMDGPU reset support along with ACP support for i2s audio with Carrizo APUs and various optimizations for command submission (CS), GPU VM, and the GPU scheduler. There isn't any explicit performance improvements made known with the DRM Radeon/AMDGPU changes for Linux 4.6, but given the various low-level optimizations and reader curiosity, I decided to run an onslaught of Linux 4.5 vs. 4.6 benchmarks on different AMD Radeon graphics cards.
The graphics cards used for this round of testing included a Radeon R9 285 (Tonga) and Radeon R9 Fury (Fiji) on the AMDGPU kernel driver. On the Radeon DRM driver was the Radeon R9 290 and R7 370 graphics cards. These are just some of the newer graphics cards I had available for testing. The Linux 4.5.0 stable kernel was compared to a Linux 4.6 Git snapshot after the DRM-Next merge. Mesa 11.3-devel via the Oibaf PPA on Ubuntu 16.04 x86_64 was used for the duration of the benchmarking. All of the OpenGL benchmarks conducted for this article were automated via the Phoronix Test Suite. DRI3 was manually enabled for all of the tests.