[osg-users] Fwd: OSG performance measurement

[Robert Osfield]

Hi Hannes,

There really isn't much info to go on from what you are written so
far.  Using the StatsHandler is a good first step but just the frame
rate reports doesn't tell us enough to know what is going on.

Try toggling the the high levels of stats info and then look at the
size of the update, event, cull, draw dispatch and draw GPU.

Another thing to do is switch off vsync via the driver and see what
the framerate is without vysunc on.

Try with a range a models.  As a general note, the OSG with 980Ti
should perform pretty well even for very large models.  I develop
under Kubuntu and find the NVidia drivers work pretty well, it has to
be a pretty serious model to get the frame rate down as low as
30-40fps, this requires ten's of millions of vertices per frame to be
rendered or high res volume rendering.  With an small scene such as
the OpenSceneGraph-Data's cow.osgt I get 6000+fps on a 1920x1080
display.

Robert.

On 17 October 2016 at 16:05, Hannes Naude <naude.jj at gmail.com> wrote:
> OK. Scratch that, I no longer believe that this is a performance measurement
> issue, but rather a performance issue. I have replaced my measurement code
> with the built in StatsHandler class, so my code now looks as follows:
>
> int main() {
> ref_ptr<osgViewer::CompositeViewer> viewer=new osgViewer::CompositeViewer();
> ref_ptr<osgViewer::View> view1 = new osgViewer::View;
> viewer->addView(view1);
> view1->addEventHandler( new osgViewer::StatsHandler );
> return viewer->run();
> }
>
> When I press S statshandler reports 30-40fps. Obviously there is not a lot
> of room to have messed up in a 5-liner program, so I believe that that is
> the actual framerate that I am getting. Question is why. I am running on a
> NVIDIA Geforce 980Ti under Ubuntu 14.04 with nvidia driver version 352.63) .
> I have optimization on (-O3 under gcc)  and believe that I am linking
> against release libraries not debug ones.
>
> Any ideas where to look??
>
> Regards
> Hannes
> ---------- Forwarded message ----------
> From: Hannes Naude <naude.jj at gmail.com>
> Date: Mon, Oct 17, 2016 at 1:46 PM
> Subject: OSG performance measurement
> To: OpenSceneGraph Users <osg-users at lists.openscenegraph.org>
>
>
> Hi all
>
> New to OSG so apologies if this is a stupid question.
>
> I have written a visualization tool in OSG and as a last step, I wish to
> ensure that it runs at the screen refresh rate. My perception was that it
> mostly runs smoothly but stutters every few frames or so, so I wrote code to
> print the elapsed time between every two frames, rather than just the
> average framerate. The printout seemed to confirm this, so I gradually
> removed more and more of my scenegraph, trying to determine where the
> bottleneck lies. The weird thing is that I end up with a completely empty
> scenegraph (just rendering a blue screen) and execution time STILL seems to
> stutter. So, I strongly suspect that there is something fundamentally wrong
> with the way I am measuring. I realise that FPS is a bad performance metric,
> but right now I just want to get to the point where I am updating every
> frame on my hardware and I am not particularly concerned about performance
> on any other hardware. The remaining code looks like this:
>
> int main() {
> ref_ptr<osgViewer::CompositeViewer> viewer=new osgViewer::CompositeViewer();
> ref_ptr<osgViewer::View> view1 = new osgViewer::View;
> viewer->addView(view1);
> float timeNow,timePrev=0;
> while (!viewer->done())
> {
> viewer->frame();
> timeNow=osg::Timer::instance()->time_s();
> std::cout << timeNow-timePrev << " ";
> timePrev=timeNow;
> }
> return(0);
> }
>
> and the resulting printout to the console looks like this:
>
> 0.123003 0.00298501 0.000751987 0.016045 0.083418 0.038128 0.013075
> 0.00068298 0.014678 0.019825 0.013804 0.016688 0.01651 0.066802 0.023197
> 0.07995 0.013019 0.000387967 0.0331 0.000599027 0.03273 0.000575006 0.088067
> 0.083023...
>
> As you can see, the loop occasionally takes as much as 88ms to complete,
> while at other time completing within 0.6ms. What could possibly be causing
> this massive variation?
>
> Regards
> Hannes Naude
>
>
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