DRI2 vs. DRI3 Radeon Linux OpenGL Performance
Following the recent Phoronix article about the state of DRI3 for X.Org drivers, many in the forums began discussing DRI3. While the Intel and Radeon X.Org drivers don't yet enable Direct Rendering Infrastructure 3 by default, I decided to run some fresh OpenGL benchmarks with a few Radeon graphics cards to compare the performance of DRI2 and DRI3.
I ran the tests from an Ubuntu 15.10 64-bit system once switching over to the Linux 4.3 Git kernel and upgrading to Mesa 11.1-devel + LLVM 3.8 SVN using the Padoka PPA. Tested for this comparison were the Radeon HD 6870, R9 290, and R7 370. However, for the R7 370 there were some general stability issues (both under DRI2 and DRI3) so for that re-branded graphics card, not all of the test results were available.
Enabling the DRI3 support with a modern Linux graphics stack for the xf86-video-ati DDX can be done by simply adding Option "DRI3" "1" to your xorg.conf/xorg.conf.d (along with disabling SwapBuffersWait as always if benchmarking).
After rebooting or just restarting the X.Org Server, you can see if DRI3 support is enabled via the Xorg.0.log.
The three Radeon graphics cards were tested with both DRI2 and DRI3 while running various Linux OpenGL benchmarks via the automated Phoronix Test Suite benchmarking software.