Trying R600g On Mesa 11.3, Cayman GPU On Linux 4.7 Radeon DRM Yields Problems
Written by Michael Larabel in Mesa on 20 May 2016 at 07:53 AM EDT. 12 Comments
MESA --
For those curious whether Mesa 11.3 improves the performance at all for users bound to an old AMD Radeon graphics card using the R600 Gallium3D driver, I have some tests of that to share this morning.

As I've been delivering many RadeonSI tests already for newer GCN GPUs on Mesa Git, I decided to run some fresh tests when using R600g for pre-GCN (Radeon HD 6000 series and older support) on Mesa Git. Like the other comparisons, I compared Mesa 11.3-devel from the Padoka PPA to Mesa 11.2 offered by Ubuntu 16.04 LTS out-of-the-box. I also then ran more Mesa 11.3 tests when upgrading from Xenial's stock Linux 4.4 kernel to Linux 4.7 drm-next code for the Radeon kernel driver.

For the testing I used a FirePro V7900 "Cayman" graphics processor, similar to the consumer Radeon HD 6900 series. The HD 6900 and HD 5800 series continue to be the lone series supporting OpenGL 4 on the R600g driver. With Mesa 11.3, it's still at OpenGL 4.1 support for these few graphics processors while the other Radeon HD 6000 series (Northern Islands) hardware is left out due to R600g not having floating point emulation support.

There wasn't much change with going from Mesa 11.2 to 11.3-devel for this Cayman GPU on R600g... But there was a heck of a difference in going from Linux 4.4 to the latest DRM-Next code. However, the performance was in the wrong direction. Many of these OpenGL tests regressed.

I don't know immediately if these regressions are from the DRM-Next code or were hitting this old GPU in the Linux 4.5 or 4.6 cycles, but nevertheless they are active on Git.

Xonotic particularly takes a bad tumble with the newer kernel.

But in some synthetic tests, there's actually an improvement with the newer kernel.

Until I have more information, you can view all the results on OpenBenchmarking.org.
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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 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 OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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