1 Reply Latest reply on Feb 28, 2014 4:17 PM by bkloppenborg

    2x performance decrease in OpenGL when OpenCL interop is enabled on R290x

    bkloppenborg

      Greetings,

       

      I have an ATI R9 280x GPU running on an Ubuntu 13.10 x86_64 system with the Gnome display manager. I have found my OpenCL/GL application runs much slower on this card than a two year old nVidia GPU. I have tracked it down to a 2x rendering performance decrease that is associated with the creation of an OpenCL/OpenGL interop context. This slow down does not happen on on my other two machines with (3+ year old) nVidia-based GPUs. Unfortunately I don't have any other ATI GPUs on which I can test this so I'm not sure if this is a driver bug or something wrong in my context initialization.

       

      Here's the output of my testing code. On my R9 280x system:

       

      bkloppenborg@epsilon:~/workspace/simtoi-model-dev/bin$ ./gl-benchmark

      Number of Elements: 5100

      Running benchmark. Press ESC after a few seconds.

      Frames: 72703

      Time (s): 6.4246

      FPS: 11316.4

      bkloppenborg@epsilon:~/workspace/simtoi-model-dev/bin$ ./clgl-benchmark

      Number of Elements: 5100

      Running benchmark. Press ESC after a few seconds.

      Frames: 40024

      Time (s): 6.97677

      FPS: 5736.75

       

      I've repeated the test several times and have obtained similar results each time. For comparision, a much older nVidia card has essentially no difference between the two programs:

       

      baron@firefly:~/SOFTWARE/simtoi-model-dev/bin> ./gl-benchmark

      Number of Elements: 5100

      Running benchmark. Press ESC after a few seconds.

      Frames: 9948

      Time (s): 9.58127

      FPS: 1038.28

      baron@firefly:~/SOFTWARE/simtoi-model-dev/bin> ./clgl-benchmark

      Number of Elements: 5100

      Running benchmark. Press ESC after a few seconds.

      Frames: 14243

      Time (s): 13.5421

      FPS: 1051.76

       

      A minimal example can be found here: https://github.com/bkloppenborg/simtoi-model-dev with the tag AMD_Dev_Central_CLGL_Slowdown .


      git clone bkloppenborg/simtoi-model-dev · GitHub

      cd simtoi-model-dev

      git checkout tags/AMD_Dev_Central_CLGL_Slowdown


      The remaining building instructions and prerequisites can be found in the README.md file. After the programs are built, run the bin/clgl-benchmark and bin/gl-benchmark programs.


      Thank you for your reply.

      Brian