I am so glad that someone else is getting the same results as we are. I've seen these same kind of gaps with our game and they come and go as I have not been able to nail down the cause for them yet. My guess is that there is some external CPU I/O activity which is causing this, especially if the graph representation works like a profiler class. The last time I profiled (I think around 8482) the threads looked very clean especially with minimal critical section usage.
I guess the question for you, is can you profile your external CPU activity? I use QueryPerformanceCount() and clock the time used for external code. I know for instance that collision detection has been expensive, and thus causes the gaps. Aside from this, if you have a Win32 platform you may use SystemInternals tools like process monitor (formerly known as filemon) to ensure your app is not doing some unexpected I/O operation. I know for instance that the trailed smoke particle effect will continuously reload the image file everytime it is used... I wouldn't have found this if it wasn't for filemon. Perhaps there is some other implicit I/O surprise which is happening to you. I hope you can rule out the external workload, because perhaps there is some performance change that we all can benefit from. :) ----- Original Message ----- From: "Bob Balfour" <[EMAIL PROTECTED]> To: "OpenSceneGraph Users" <[email protected]> Sent: Monday, July 07, 2008 5:37 PM Subject: [osg-users] Rendering performance issues > I'm experiencing some performance peculiarities that I don't quite > understand. My platform is an HP Blackbird, Vista OS, 4-CPU, 2 NVidia > 8800, OSG2.4. > > I have attached 4 timing images: > > The first image (vsyncOFF-1GPU.jpg) shows the timing rendering 1 slave > camera on an extended (2880x900) dual-monitor on a single Nvidia card. > Note the 211Hz rendering rate with VSync off and the substantial > Draw/GPU overlap. [Note that in all of these timing tests none of the > CPUs appeared more than 50% loaded.] This is the type of performance I > was anticipating. > > Now all I did was turn on Vsync. The second image > (vsyncON-app-long.jpg) now shows a 60Hz rendering rate as expected (with > a delay after GPU waiting for VSync), but no Draw/GPU overlap, there's > even a slight gap between the two? Why is this different now? > > Now I flew thru the scene to a point where the Draw became quite small. > The third image (vsyncON-app-short.jpg) shows the Cull,Draw,GPU all > <1.0, but I'm only achieving a 46Hz rendering rate because of the > considerable gap between Draw and GPU. Why is the GPU now being delayed > so much after Draw?? It's almost like the GPU is stuck starting out > there mid-frame? > > Now I turned VSync back OFF, but this time rendered TWO slave cameras > (each 2880x900, one on each Nvidia card), and the same effect appeared > (see the forth image vsyncOFF-2GPUs.jpg) where the GPUs are being > delayed to mid-frame, and there is quite a delay after the GPUs complete > (which should not be there with VSync OFF?). Because of these > substantial delays which I don't understand, performance has degraded > considerably from my initial test image, which had good overlap and no > delays. > > Is there any explanation for this, and can the delays be eliminated and > performance improved? > > Also, is there a purpose/need for VSync using LCD flatpanel monitors or > DLP projectors? > > Thanks. > > Bob. > -- > > Robert E. Balfour, Ph.D. > Exec. V.P. & CTO, BALFOUR Technologies LLC > 960 So. Broadway, Suite 108, Hicksville NY 11801 > Phone: (516)513-0030 Fax: (516)513-0027 email: [EMAIL PROTECTED] > /"Solutions in four dimensions" with *fourDscape*®/ > > ---------------------------------------------------------------------------- ---- ---------------------------------------------------------------------------- ---- ---------------------------------------------------------------------------- ---- ---------------------------------------------------------------------------- ---- ---------------------------------------------------------------------------- ---- > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org > _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
