[osg-users] performance mystery with an osg::TerrainTile on nVidia. Intel wins.

[Christian Buchner]

Found the culprit for my performance woes. The nvidia driver's GLX module
for Xorg was likely overwritten by an update to xorg. This caused the GLX
module initialisation to fail and the following lines to appear in the log
file.

[   873.392] (EE) NVIDIA(0): Failed to initialize the GLX module; please
check in your X
[   873.392] (EE) NVIDIA(0):     log file that the GLX module has been
loaded in your X
[   873.392] (EE) NVIDIA(0):     server, and that the module is the NVIDIA
GLX module.  If
[   873.392] (EE) NVIDIA(0):     you continue to encounter problems, Please
try
[   873.392] (EE) NVIDIA(0):     reinstalling the NVIDIA driver.

[   874.171] (II) AIGLX: Screen 0 is not DRI2 capable
[   874.171] (EE) AIGLX: reverting to software rendering
[   874.177] (II) AIGLX: Loaded and initialized swrast
[   874.177] (II) GLX: Initialized DRISWRAST GL provider for screen 0

The OpenGL system therefore reverted to software rasterization.

What I do not understand is why the command "glxinfo" kept showing NVIDIA
Corporation as vendor for OpenGL in this case.

After reinstalling the nVidia driver, my draw times for the terrain tile
are in the range of 0.2 ms. Yay. In your face, Intel.

Christian



2015-09-17 16:05 GMT+02:00 Christian Buchner <christian.buchner at gmail.com>:

> Hi all,
>
> I am loading a single osg::TerrainTile into my scenegraph, as a child of
> an osg::Terrain. Into this tile goes a height field and one image layer.
>
> I have got around 80k vertices and 157k triangles in a single drawable
> that is marked as a "fast" drawable in the OSG stats handler (shown by
> using the s hotkey)
>
> While this application runs butter smooth on Intel integrated graphics (60
> FPS), I am experiencing somewhat of a mystery slowdown on nVidia GTX 970
> and an nVidia GT 750M.
>
> 5 FPS and draw times of 170ms upwards on the 750M for example.
> This is on Ubuntu 12.4 with nVidia driver 331.113
>
> 10 FPS and draw times of 78ms upwards on the GTX 970M.
> This is on Ubuntu 12.4 with nVidia driver 346.46
>
> The geometry created by src/osgTerrain/GeometryTechnique disables display
> lists and uses vertex buffer objects. It's referencing a vertex buffer
> using a single osg::DrawElementsUInt(GL_TRIANGLES).
>
> The slowdown is a mystery. Any ideas what might be going on here? Why
> would the nVidia driver be hitting such a slow code path? In terms of
> geometry complexity, 80k vertices and 157k triangles is a joke even for
> today's entry level GPUs.
>
> Let me know if you need some code for repro'ing.
>
> Christian
>
>
>
>
>
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