[Opensim-dev] Sim and Phys Frames per Second (FPS) Issues
Diva Canto
diva at metaverseink.com
Mon Mar 2 21:31:07 UTC 2015
BTW, I don't know why the stats reporter multiplies by a factor, maybe
to stay backwards compatible with some perception that people expected?
Simulation FPS is supposed to be constant. In the case of OpenSim, the
user experience doesn't change if we increase this rate beyond 11/sec.
If it goes below that, however, then that's a sign that the simulation
is stressed.
I refer anyone interested in this to documentation about simulations in
general. Here's a good tutorial that I point students to in one of my
courses:
http://buildnewgames.com/real-time-multiplayer/
Scroll down to the part about "game loops"
On 3/2/2015 11:16 AM, Sean M 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
> <mailto: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
>> <mailto: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.
>>
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>>
>>
>>
>> --
>> Michael Emory Cerquoni
>>
>>
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