Marek Takes To RadeonSI Tweaking For Unigine Superposition
Written by Michael Larabel in Radeon on 22 June 2017 at 02:43 PM EDT. 40 Comments
It looks like one of the latest test targets for well known AMD open-source developer Marek Olšák is Unigine Superposition.

Unigine Superposition, released earlier this year for Windows and Linux, is a beast on OpenGL drivers and all current generation graphics cards. Superposition is one of the workloads that hasn't been well optimized yet for RadeonSI and is where the open-source AMD stack struggles compared to the competition.

Fortunately, it looks like Marek is now eyeing Superposition for RadeonSI improvements.

Today he posted a new patch to enable sisched for Superposition. Sisched is the LLVM SI machine instruction scheduler that has been around for a while but isn't enabled by default, but requires setting R600_DEBUG=sisched.

Marek's patch would enable sisched by default where the process name is superposition. This application-specific switch would be hard-coded into the RadeonSI code rather than being a drirc tunable.

Marek noted in the patch, "+2.3% better score on Fiji. It might be better without HBM." Curious about the impact of sisched for Unigine Superposition, I ran some benchmarks:

A Radeon RX 470 with Mesa 17.2-dev Git on Linux 4.12:

Indeed, some minor gains, though in some scenarios the sisched results were flat. All of the Superposition benchmarks I ran today via this result file.
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Michael Larabel is the principal author of and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and automated benchmarking software. He can be followed via Twitter or contacted via

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