DRI3 Improvements Land In Mesa Git
There is now EGL DRI3 X11 support, which was implemented using a new DRI3 helper library. With that helper library having landed, the GLX DRI3 code was adapted to make use of it too.
With today's DRI3 push in Mesa, EGL/X11 DRI3 code was also hooked up to implement EGL_KHR_image_pixmap support.
For the performance impact of using DRI3, see our recent DRI3 vs. DRI2 Radeon comparison. DRI3 is also a requirement for Vulkan support on the X.Org Server.