[Opensim-dev] Phantom prims and memory usage?

[Dahlia Trimble]

Phantom prims do not require a "proxy", which is an in-memory representation
of the object used to compute collisions. Proxy memory usage is directly
related to prim complexity, and simple boxes and spheres are the most memory
efficient. Memory requirements increase as prims are reshaped and features
such as hollows and cuts are used. To get a rough idea about what is
happening, observe a prim in wireframe mode in the SL viewer (ctrl-shift-R)
and edit a prim, varying the available parameters in the editor. Each
intersection of lines results in a "vertex" and each triangle formed are the
individual elements which use memory. Note that the sl viewer uses more of
these elements than the equivalent proxy on the server uses, as additional
elements can be used to display higher quality shading effects on the
display.
Due to the nature of "unmanaged" memory usage between the ODE library and
the "managed" use in the OpenSim code base, it is unclear how well each
run-time environment (mono or .NET framework, or version differences) is
able to reclaim memory that was once used for a prim that is now phantom. If
one is attempting to characterize memory usage the results will most likely
vary between these environments. Also, restarting the simulator process may
in some cases show an improvement.

One other factor to consider is the Garbage Collection (GC) policies of each
run time environment are also inconsistent, and memory usage displays such
as "top" in linux systems and the windows task manager may be quite
inaccurate.


On Mon, Feb 23, 2009 at 7:13 AM, John Sheridan <john at pseudospace.net> wrote:

> Ok, I'm trying a little bit of an experiment here and I'm wondering if
> anyone else has tried this and had similar results?  We're running ODE
> on Linux Ubuntu using a vps setup hosted on quad core Xeons.
>
> I'm going on the concept that if an object does not need any sort of
> physical interaction that if its made phantom the server will in effect
> use less resources.  In this case I have one server thats running six
> sims with around 30,000 prims spread between them all.  After going
> around and setting as many objects as possible to phantom (telephone
> poles, windows, tables, chairs, misc props and anything thats not needed
> to keep the avatar from falling out of the buildings) it appears as
> though that server's memory usage has gone down from about 70% (740
> megs) down to 45% (520 megs).  I would estimate that in total
> approximately 15,000 to 20,000 prims were set to phantom.
>
> Thanks, :)
>
>  - John / Orion Pseudo
>
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