DRI3 is not the default setting (Skylake GT2)
While trying to work out an issue with Mesa 20.0.0 with iris using the intel display drivers mesa/mesa#2569 (closed) I discovered that it appears that DRI 3 is not being used by my Mesa Intel(R) HD Graphics 530 (SKL GT2).
I tested an intensive video game process running simultaneously the same cut scene over and over in a controlled environment while glxgears is running.
Here are the results of this test in i965 environment:
- 5747.7040877193 FramesPerSecond [blank - i.e. no dri setting specified (default)]
- 5968.33305263158 FramesPerSecond Option "DRI" "3"
- 5717.58489473684 FramesPerSecond Option "DRI" "true"
- 5710.27394736842 FramesPerSecond Option "DRI" "2"
- 514.665578947368 FramesPerSecond Option "DRI" "1" (not a typo ~500 lol)
- 515.992 FramesPerSecond Option "DRI" "false"
- 528.772 FramesPerSecond Option "DRI" "off"
- 5550.83156140351 FramesPerSecond Option "DRI" "none" (appears like it reverts to default i.e. what looks like DRI 2)
- 514.397 FPS FramesPerSecond Option "DRI" "0"
Everywhere you search on the internet they say that DRI3 is the default behavior for xf86-video-intel drivers. Clearly, something with my setup suggests that isn't the case. As soon as I explicitly wrote the option "DRI" "3" the artifacts and text corruption on Mesa 20.0.0 with iris went away as well.
Is it a known thing that on some older cards Ubuntu (or some other setting, xf86-video-intel, etc) uses DRI 2 in place of 3 as the default? Using DRI2 is a huge performance drop! Who can solve this? What can we do?