Trying Out RadeonSI NIR With Some OpenGL Linux Games On Mesa 18.1-dev
Written by Michael Larabel in Mesa on 30 January 2018 at 07:07 PM EST. 26 Comments
MESA --
With the RadeonSI NIR back-end continuing to mature with more OpenGL coverage and now supporting GLSL 4.50, I decided to run some tests of Mesa 18.1-dev Git to see the impact when enabling NIR support.

The RadeonSI NIR support remains disabled by default at this time. Those using recent versions of Mesa can enable this experimental intermediate representation code path by enabling R600_DEBUG=nir. Tests were done from an Ubuntu 17.10 x86_64 box with the Linux 4.15 Git kernel and Mesa 18.1-dev obtained today via the Padoka PPA.

These tests were done on a Radeon RX Vega 56 with/without the NIR support.

First up, when using the NIR support, both Dawn of War III (when using high settings) and Deus Ex: Mankind Divided (in any configuration tested) hung while on their respective loading screens. The same Mesa build and all other settings being the same except for not setting R600_DEBUG=nir, the games were working dine on this Radeon RX Vega system. Though it's not too surprising seeing DOW3 and Deus Ex fail right now with NIR considering these are two of the most demanding Linux games right now.


In the games that ran fine with the RadeonSI NIR code-path, there generally wasn't any real performance difference...

But the Phoronix Test Suite was also monitoring the situation to see if the CPU utilization differed, etc.




Mad Max with OpenGL was running on the RadeonSI NIR code-path, but was much slower than Mesa 18.1-dev out-of-the-box.

The CPU usage for Mad Max with NIR was also higher.

The performance with Xonotic had regressed under the NIR code.

The rest of the time, the data was uneventful:



RadeonSI NIR support is making progress, but from the time spent this afternoon testing it out, it's obviousy why this alternative IR code-path is yet to be enabled by default for this open-source AMD driver. But with this NIR back-end being needed for RadeonSI to get its SPIR-V support in order for in turn hitting OpenGL 4.6 compliance, hopefully this code matures nicely as the year moves on.

About The Author
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 10,000 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 OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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