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Radeon vs. Modesetting DDX Driver Performance On Ubuntu 16.04

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  • Radeon vs. Modesetting DDX Driver Performance On Ubuntu 16.04

    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?pag...ing-DDX-Xenial

  • #2
    Hehehe, in before bridgman calls out the Bugzilla spammer again .

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    • #3
      "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?

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      • #4
        Originally posted by Espionage724 View Post
        "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
        Last edited by Serafean; 23 April 2016, 09:39 AM.

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        • #5
          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 ?

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          • #6
            Originally posted by Scias View Post
            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
            All opinions are my own not those of my employer if you know who they are.

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            • #7
              Originally posted by Scias View Post
              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...
              I don't understand it either, however the evidence presented in the article leads me to believe that examining the software architecture and the source code of X+drivers+Mesa+etc closely would reveal what is causing the differences in performance. It must be there somewhere in the software, somebody "just" needs to find it and then optimize the code.

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              • #8
                Originally posted by Ericg View Post

                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.

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                • #9
                  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.

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                  • #10
                    Originally posted by Espionage724 View Post
                    "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.

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