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

Mon Mar 2 20:54:25 UTC 2015

I believe 11 sim FPS is the target value. It would probably never go above
this, but a number consistently lower than 11 fps would indicate
performance problems. If the "lie" is simply a linear scaling, then it
would have no impact in the ability to use the number as a comparitive
statistic. since all such numbers would be similarly scaled.

I also believe some of these numbers eventually make it to the viewers and
are used to adjust moving entity velocity when the sim is running slowly.
I'm not sure of the exact path but I think "time dilation" is involved.
Altering these values may induced undesirable movement effects when the
simulator is running slower than normal.

Raising the target above 11 would also likely induce issues as other parts
of the code assume 11 is the target.

On Mon, Mar 2, 2015 at 11:16 AM, Sean M <mondesire.sean at gmail.com> wrote:

> There are 3 frame rates: *simulation*, *physics*, and *client*. Please,
> someone correct me if I am wrong: the *simulation fps* is how many
> simulation loops can be processed in a second, where each loop processes
> physics, scripting, region updates, etc; *physics* *fps* is just how many
> physics loops get processed per second, where each loop calculates
> collisions, gravity changes, and other movement updates for all appropriate
> objects in a region Both physics and simulation (phys/sim) fps are
> server-side. The fps the *client* is concerned with is graphics rendering
> on the viewer (firestorm, singularity, etc) and is literally how many
> visual frames/shots are displayed per second to the client. From a client
> point of view, 11fps is low because that is a low amount of image updates
> the client is visually seeing on their viewer. I am concerned with the
> simulation and physics FPSs being reported with highly inflated numbers. I
> want to use sim and phy FPSs as measures of how my region is performing but
> concerned that the correctionFactor of 5 is invalidly skewing these
> metrics, making both fps useless.
>
> Michael, or anyone else, do you know why OpeSim ticks at 11 fps? Why 11?
> Is my understanding of what constitutes a "frame" correct?
>
> On Mon, Mar 2, 2015 at 1:37 PM, R.Gunther <rigun at rigutech.nl> wrote:
>
>>  11fps ? is that not very low. 22fps gives more rome or 33fps.
>> But i admit that i read fps maby wrong, and have nothing today with the
>> framerate or smoothness on the screen..
>>
>>
>>
>> On 2015-03-02 19:28, Michael Emory Cerquoni wrote:
>>
>> The reason physics and scripting are locked at 11fps is because this is
>> what the OpenSimulator heartbeat ticks at, the reason it is multiplied is
>> to satisfy the viewer statistics, I am not sure its possible to have it
>> report the legitimate numbers without some wierd side effects, but I could
>> be wrong, you would have to experiment, I suspect though that changing this
>> could lead to a lot of badness.
>>
>> On Mon, Mar 2, 2015 at 1:23 PM, Sean M <mondesire.sean at gmail.com> 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.
>>>
>>> _______________________________________________
>>> Opensim-dev mailing list
>>> Opensim-dev at opensimulator.org
>>> http://opensimulator.org/cgi-bin/mailman/listinfo/opensim-dev
>>>
>>>
>>
>>
>> --
>> Michael Emory Cerquoni
>>
>>
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