While Linux 4.9 will not officially open for development until next week, the DRM-Next code is ready to roll with all major feature work having been committed by the different open-source Direct Rendering Manager drivers. In this article is some preliminary testing of this DRM-Next code as of 29 September when testing various AMD GPUs with the Radeon and AMDGPU DRM drivers.
Linux 4.9 does bring compile-time-offered experimental support for the AMD Southern Islands GCN 1.0 hardware on AMDGPU, but that isn't the focus of this article. A follow-up comparison is being done with GCN 1.0/1.1 experimental support enabled to see the Radeon vs. AMDGPU performance difference on that hardware. For today's testing was a Radeon R7 370 to look at the Radeon DRM performance and for AMDGPU testing was the Radeon R9 285, R9 Fury, and RX 480. Benchmarks were done from the Linux 4.8 Git and Linux DRM-Next kernels as of 29 September.
Throughout testing the same Mesa 12.1-dev + LLVM SVN snapshot from the Padoka PPA was used for testing. The latest Radeon/AMDGPU from Linux-Firmware Git was also used. Aside from swapping out the GPUs and kernel version, no other changes were made while running several different OpenGL benchmarks on these four AMD Radeon graphics cards. All of the benchmarks were facilitated in a fully-automated and standardized manner using the open-source Phoronix Test Suite benchmarking software. But before getting to the numbers, a few problems encountered when testing out this early Linux 4.9 code...
The Radeon R7 370 on the DRM-Next code wouldn't display when using a DisplayPort connection to the 4K display, a feature that previously worked for this card. When using a DVI connection to the same display, it worked. The dmesg showed errors about the DPM set power state code and the DP link training.
During the benchmarking process with the R7 370, there was a heck of a lot of call traces being spewed dealing with the DRM page-flipping ioctl.
The Radeon R9 Fury during AMDGPU testing of the Linux 4.9 kernel also ran into a very big dmesg log. With the R9 Fury these traces were also about the DRM page flipping ioctl.
Keep in mind this DRM-Next code is still very early and Linux 4.9 won't be officially released for at least two months.