[Opensim-dev] Sim and Phys Frames per Second (FPS) Issues

[Justin Clark-Casey]

I think this has already been said but just to summarize.

* The 11 fps are the number of scene frames processed - opportunities where avatars may be notified about changes in the 
scene.

* Each of these scene frames is associated with a physics process where 5 physics frames are processed in each frame. 
Hence 11 * 5 = 55 fps.

* Why this number?  Others may know better but my guess is that it's related to the frequency of updates expected by the 
viewer.  Teravus may well know more if he's still around.

* Changing m_reportedFpsCorrectionFactor will do nothing except change the server FPS stat.

* Changing MinFrameTime will change the number of scene frames.  From my work in the past, you would also need to adjust 
other parameters like physics frames to stop things going haywire (this was with ODE, Bullet might work differently).  I 
expect you also wouldn't gain much if anything in scene fidelity.

On 02/03/15 18:23, Sean M wrote:
> Greetings,
>
> We at the MOSES project have noticed Simulation and Physics frames per second (FPS) have a few issues that we are trying
> to resolve. The issues are producing suspicious performance statistics for the analysis of the current version of
> OpenSim that we are running.
>
> First, there is a correction factor (m_reportedFpsCorrectionFactor) that the raw SimFPS is multiplied by. The comment in
> the following line is a bit curious because it indicates that the FPS is artificially inflated to "lie" about the actual
> FPS being so low:
>
> OpenSim/Region/Framework/__Scenes/SimStatsReporter.cs: Line 317
> // We're going to lie about the FPS because we've been lying since 2008.  The actual FPS is currently
> // locked at a maximum of 11.  Maybe at some point this can change so that we're not lying.
> int reportedFPS = (int)(m_fps * m_reportedFpsCorrectionFactor);
>
> Also, lines 174 and 227 mention the use of this correction factor.
>
> Second, this multiplier also comes into play in the Scene where there is a MinFrameTime, which seems to be the minimum
> reported amount of time to process a frame:
> OpenSim/Region/Framework/__Scenes/Scene.cs:Line 723
>
> Both of these variables, the correction factor and MinFrameTime, are concerning from a statistics view point as they are
> generating skewed and massaged numbers; therefore, I have a few questions:
>
> 1) Is it commonly known that Sim and Phy FPSs are inflated to maintain the "lie"? And if so, will it be corrected to be
> an accurate reporting of processed frames per second?
>
> 2) What exactly are the definitions for OpenSim's Simulation (Sim) FPS, Physics (Phy) FPS and a frame (I have found
> conflicting and vague definitions on the wiki)?
>
> 3) What are the known performance consequences of setting the m_reportedFpsCorrectionFactor to 1 and MinFrameTime to 0?
>
> Thanks,
> Sean M.
>
>
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-- 
Justin Clark-Casey (justincc)
OSVW Consulting
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