Test Driving AMDGPU's Performance With DRM-Next For Linux 4.13
Written by Michael Larabel in Display Drivers on 27 June 2017. Page 1 of 4. 2 Comments

With the Linux 4.13 merge window likely to open next week and the DRM-Next cutoff already having passed for new material that in turn wants to target 4.13, here are some initial benchmarks with a Polaris and Fiji graphics cards for this new AMDGPU DRM code.

The AMDGPU DRM driver updates queued for Linux 4.13 include Vega bug fixes, initial support for Raven Ridge APUs (Zen cores + Vega graphics), KIQ support for compute rings, MEC queue management rework, SR-IOV improvements, a variety of bug fixes, some new module parameters for controlling GCN 1.0/1.1 AMDGPU/Radeon DRM driver selection behavior, and more. A secondary set of work includes semaphores support using sync objects, optimizing the buffer object list ioctl, and other changes. There are lots of internal code changes, Vega fixes, and other technical work, but not too much for end-users to get excited about on AMDGPU for the Linux 4.13 front.

Notably still absent from AMDGPU is the long-awaited DC (DAL) display support... Thus with Linux 4.13 you still don't have HDMI 2.0, FreeSync, and notably HDMI/DP audio for newer AMD graphics cards among other display features not being present like atomic mode-setting. Also, another notable hindrance without DC/DAL is no display support for Vega. So if you plan to pick up a Radeon RX Vega graphics card next month, you'll either need to be using the AMDGPU-PRO hybrid driver with its DKMS module, building your own kernel from the DC testing tree, or using an Intel+Vega combination or the like to use DRI PRIME to drive the display from a non-Vega GPU. It's less than ideal, but that appears to be the only -- albeit very significant -- limitation for Vega Linux support at launch. Hopefully we will see DC for Linux 4.14, but that still isn't clear and AMD developers aren't willing to publicly say when they hope it will be merged to mainline.

For seeing if there's any performance impact from the AMDGPU changes queued in DRM-Next, I ran some benchmarks of it compared to the Linux 4.12 mainline Git code. This was while using Mesa 17.2-dev via the Padoka PPA on Ubuntu 17.04. A Radeon RX 580 (Polaris Evolved) and R9 Fury (Fiji) graphics cards were used for this initial comparison. More Linux 4.13 kernel benchmarks will come once this next kernel cycle is officially underway.

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