Radeon vs. Modesetting DDX Driver Performance On Ubuntu 16.04

[phoronix]

Phoronix: Radeon vs. Modesetting DDX Driver Performance On Ubuntu 16.04

Following the quick DRI2 vs. DRI3 rendering tests with Radeon on R600g, I also did tests on the same system of the xf86-video-ati vs. xf86-video-modesetting DDX drivers...

http://www.phoronix.com/scan.php?page=news_item&px=Radeon-Modesetting-DDX-Xenial

[pq1930562]

Hehehe, in before bridgman calls out the Bugzilla spammer again .

[Guest]

"Older chips don't have the necessary functionality to support glamor." Which chips? I run modesetting on a HD2400 currently, but perhaps older chips means even older than that?

"R600 and newer could eventually move to -modesetting once all the features from -ati get ported to -modesetting." What features are missing?

[Serafean]

"Older chips don't have the necessary functionality to support glamor." Which chips? I run modesetting on a HD2400 currently, but perhaps older chips means even older than that?

"R600 and newer could eventually move to -modesetting once all the features from -ati get ported to -modesetting." What features are missing?

I'd wager r300g class hardware. xf86-video-ati supports even those grandpas

[Scias]

I don't really understand why there is or even should be a difference between using the modesetting or radeon/nouveau DDX drivers as these are the X drivers hence not used for gaming/3D stuff... unless the benchmarks are done windowed and in a composited WM ?

[Ericg]

I don't really understand why there is or even should be a difference between using the modesetting or radeon/nouveau DDX drivers as these are the X drivers hence not used for gaming/3D stuff... unless the benchmarks are done windowed and in a composited WM ?

The DDX drivers control which version of DRI you use, and therefore how the images get displayed on the screen. Pretty sure DRI still affects performance even without a composited WM running

[Scias]

The DDX drivers control which version of DRI you use, and therefore how the images get displayed on the screen. Pretty sure DRI still affects performance even without a composited WM running

That makes sense for DRI2 vs DRI3, but modesetting is slightly ahead of radeon-DRI3 despite both using the same DRI version, that's the thing I don't really understand since the 2D/DDX codepaths shouldn't matter in games.

[Mangix]

The way I've come to understand it is that the modesetting driver is more "direct". That is, it's a wayland equivalent for X11 in terms of requiring KMS.

[drSeehas]

"Older chips don't have the necessary functionality to support glamor." Which chips? I run modesetting on a HD2400 currently, but perhaps older chips means even older than that? ...

Yes. HD2400 is R600 generation.

[gururise]

Any benefit to using one driver over the other at this point? Being forced to upgrade to 16.04 from 15.10 soon, and will be forced again to switch from fglrx to radeonsi. I would like to choose the driver that will continue to allow me to run most of my steam games. Are either of these drivers more compatible than the other with steam games?