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

[Sean M]

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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