Trying Out RadeonSI NIR With Some OpenGL Linux Games On Mesa 18.1-dev
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.
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