Enabling DRI3 Is Still An Easy Performance Hack Relevant For Ubuntu 16.04 Systems
While some distributions like Fedora have opted to enable DRI3 by default with their (mostly Intel) X.Org driver packages, Ubuntu 16.04 didn't pursue such behavior. But that just means with an easy xorg.conf tweak you can generally get better performance unless you happen to hit one of the few remaining DRI3-related issues.
It's as easy as adding Option "DRI" "3" to your xorg.conf or xorg.conf.d file for enabling Direct Render Infrastructure 3 rather than the DRI2 default for Radeon and Intel driver configurations.
As has been covered by numerous past Phoronix articles, enabling DRI3 generally leads to better performance. Ubuntu 16.04 LTS is shipping X.Org Server 1.18.3 by default along with all the latest DDX drivers so generally most people should be happy with having DRI3 enabled since the early DRI3/Present fallout should mostly be addressed.
With DRI3 enabled, Linux gamers can see some performance boosts like:
I did some quick tests with a Cayman GPU on R600g from Ubuntu 16.04 with DRI2 vs. DRI3 via this new OpenBenchmarking.org result file. You can see some of our past DRI3 benchmarks for Intel HD Graphics and DRI3 Radeon tests for more details. It's an option worth testing out on Ubuntu 16.04 and other newer distributions to see if it benefits your workloads while yielding no regressions.