Given this weekend's release of Darktable 2.2 as a big upgrade to this open-source RAW photo workflow software, here are some fresh benchmarks of NVIDIA GeForce and AMD Radeon graphics cards under Linux when making use of the program's OpenCL support, which did see some improvements during this v2.2 cycle.
For those pondering about what GPUs offer the best OpenCL performance for Darktable 2.2 or the impact the different GPUs can make with this GPGPU acceleration, hopefully you find these reference numbers useful that I just finished up. All of the NVIDIA GPUs were tested with the latest NVIDIA 375.26 driver. The NVIDIA GPUs benchmarked were the GTX 650, GTX 680, GTX 750, GTX 760, GTX 780 Ti, GTX 950, GTX 960, GTX 970, GTX 980, GTX 980 Ti, GTX 1050, GTX 1050 Ti, GTX 1060, GTX 1070, and GTX 1080.
On the AMD side was the latest AMDGPU-PRO 16.50 release that's public. The open-source stack wasn't tested since AMD admits the Clover-based implementation being rather poor and not recommended for testing. Once the ROCm stack with its new OpenCL stack is fully open, that will be used for future tests, but for today we just have the OpenCL binary driver provided by AMDGPU-PRO. With AMDGPU-PRO 16.50 there is GCN 1.0 experimental support, but it still runs into some issues during my OpenGL tests but the tested GCN 1.0 graphics cards did end up working fine for this Darktable OpenCL benchmarking. The AMD GPUs for testing were the Radeon HD 7950, R7 260X, R9 285, R9 290, R7 370, RX 460, RX 480, and R9 Fury.
All of these Darktable OpenCL Linux benchmarks were carried out in a fully-automated manner using the open-source Phoronix Test Suite benchmarking software.