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<div class="moz-cite-prefix">On 11/14/2014 8:46 AM, Maxwell, Douglas
CIV USARMY ARL (US) wrote:<br>
</div>
<blockquote
cite="mid:180878FAC40F8447ADED7BA2DE0775FD1615C3D1@ugunhpso.easf.csd.disa.mil"
type="cite">
<pre wrap="">Classification: UNCLASSIFIED
Caveats: NONE
Dr. Lopez, thank you for sharing your paper. Can you tell me where it was
peer reviewed and published? I would like to reference it in my
dissertation.</pre>
</blockquote>
<br>
Gabrielova, E., Lopes, C. V. (2014). Impact of Event Filtering on
OpenSimulator Server Performance. In Proceedings of the 2014 Summer
Simulation Multi-Conference. Summer Simulation Multi-Conference
(SummerSim), USA. The Society for Modeling & Simulation
International.<br>
<br>
<blockquote
cite="mid:180878FAC40F8447ADED7BA2DE0775FD1615C3D1@ugunhpso.easf.csd.disa.mil"
type="cite">
<pre wrap="">On the topic of bots, the MOSES team has not been able to compose a NPC
agent or bot that accurately replicate the footprint of a human agent on the
simulator. </pre>
</blockquote>
<br>
They don't, and that's not how you should look at them. They are
artificial, highly controlled versions of viewers. They are lab
experiments. You can make them behave *exactly* how you want them to
behave, down to the number of AgentUpdates per second, so all
experimental conditions are under your control -- as opposed to
using real viewers driven by real people, which becomes impossible
to formulate what exactly they are doing. Testing with real people
gives you a *qualitative* view of how things are performing, and
that's very important, but it doesn't give you a sharp
*quantitative* view of what's going on. <br>
<br>
You should look at bot experiments as laboratory experiments in the
pharmaceutical industry. A very important first step with which you
can test a multitude of things in a highly controlled environment
before doing clinical tests with humans. The lab experiments will
point you to the most critical bottlenecks, and they are
quantifiable.<br>
<br>
You don't necessarily need to run the bots on the same network as
the server. You can run them from amazon ec2 instances in different
parts of the world.<br>
<br>
Bots have proven invaluable for improving the performance of OpenSim
leading to the conferences. I used them last year, and Justin has
used them even more this year.<br>
<br>
<br>
<blockquote
cite="mid:180878FAC40F8447ADED7BA2DE0775FD1615C3D1@ugunhpso.easf.csd.disa.mil"
type="cite">
<pre wrap="">We believe this is for many reasons:
1) Bots are usually composed on a server on the same network, not dispersed
across the internet. The bots should be software throttled and noise
introduced into their connections to approximate random access.
2) Bots aren't using full clients, so they are not filling caches and
making the same scene requests as humans in graphical clients.
3) Bots are usually homogenous. They need to be randomly dressed, have
random attachments, and have random inventories.
4) Bots need to move randomly and collide with objects in the scene and
with each other.
5) Bots need to randomly chat with each other and broadcast locally.
We think we can create a NPC solution that satisfies these issues. Will
take some thought and development. Has anyone come close to this?
Goal: Compose bots/NPCs that can approximate the loads of humans within 90%
certainty. Meaning if we load 100 of these artificial agents into the
MOSES, we are certain that it will accurately behave as if at least 90
humans are logged in.
IMHO, if you can't assign a reliability to a test, then you are just wasting
your time. This is basic V&V tenants.
v/r -douglas
Douglas Maxwell, MSME
Science and Technology Manager
Virtual World Strategic Applications
U.S. Army Research Lab
Simulation & Training Technology Center (STTC)
(c) (407) 242-0209
-----Original Message-----
From: <a class="moz-txt-link-abbreviated" href="mailto:opensim-dev-bounces@opensimulator.org">opensim-dev-bounces@opensimulator.org</a>
[<a class="moz-txt-link-freetext" href="mailto:opensim-dev-bounces@opensimulator.org">mailto:opensim-dev-bounces@opensimulator.org</a>] On Behalf Of Diva Canto
Sent: Friday, November 14, 2014 11:05 AM
To: <a class="moz-txt-link-abbreviated" href="mailto:opensim-dev@opensimulator.org">opensim-dev@opensimulator.org</a>
Subject: Re: [Opensim-dev] Modifying the networking stack
On 11/14/2014 6:23 AM, Michael Heilmann wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Thanks for the responses. I'll go into a little more detail:
We have been running several profilers against OpenSimulator on the
MOSES grid, and on my development machine. The tests were to examine
the loading on the server under several different loads, specifically
mesh and physics loads. What we found appears to be that no matter
what kind of load we placed on the region, even to the point of
becoming unresponsive due to physics and mesh, that scripting and
physics load were nowhere near the amount of time spent in
OpenSim.Region.ClientStack.LindenUDP once we had more than one or two
avatars logged in. We know from previous investigations at our
firewall that network traffic for OpenSim is not that heavy,
especially with low numbers of users.
</pre>
</blockquote>
<pre wrap="">
If this is a problem, and you are running a recent-ish version of core
OpenSim, it sounds like some misconfiguration somewhere. Back in the summer
of 2013 we had a problem with the server running OSCC'13; the kernel was
configured to run in some sort of special mode that was making everything
run badly and unpredictably. We fixed the kernel configuration, and suddenly
things started running much more smoothly-- I don't remember the details,
but Nebadon may clarify things.
OpenSim these days can handle 50 people on a single simulator without much
trouble. If you look at figure 7 of my paper
(<a class="moz-txt-link-freetext" href="http://www.ics.uci.edu/~lopes/documents/summersim14/gabrielova_lopes_prepri">http://www.ics.uci.edu/~lopes/documents/summersim14/gabrielova_lopes_prepri</a>
nt.pdf)
you will see the quantification of "without much trouble." I suggest that
you reproduce my experimental conditions with pCamBot and check whether your
numbers are very different from ours. If they are very different, then
there's definitely something odd in your setup, as we were able to reproduce
these numbers in several machines. Feel free to contact me directly for
details about pCamBot configuration.
Bots aren't real viewers, but they are much better for measuring things
systematically and detecting problems and bottlenecks than relying on real
users driven by real people. The performance you get with pCamBot will be
correlated with the performance you get with real users.
</pre>
<blockquote type="cite">
<pre wrap="">I ran several Wireshark captures against a Firestorm viewer logging
into the MOSES public grid ABWIS region, where we hold our office
hours. I saw that with our current configuration, all traffic between
the server and my client, with the exception of http CAPS and fsapi
calls, were UDP traffic. This is not immediately concerning, as we
have simian serve our mesh and textures directly. The messages are
mostly binary information, so I could not examine closely, but I did
see a lot of messages containing identical ASCII strings, such as the
name of my avatar.
</pre>
</blockquote>
<pre wrap="">
Hard to say what you saw, but I bet those are the AgentUpdate messages that
I mentioned before. The viewer sends at least 10/sec. At points, the viewer
sends much more than 10/sec, up to 60/sec. Again, take a look at my paper
for understanding what those are, and how OpenSim deals with them since
OSCC'13.
As I said before, it would be nice to understand why the viewer is so eager
to blabber its status to the server when nothing is going on.
</pre>
<blockquote type="cite">
<pre wrap="">My primary concern is the amount of time spent handling networking,
not necessarily the networking its-self. But there is at least a
portion of messages on the UDP pipeline that are either reliable, or
perhaps should be; and re-implementing a reliable transport over udp
introduces load at the application layer, instead of letting a
low-level reliable transport such as tcp handle it. I went to
university with a guy who implemented a java networking library
completely over UDP, believing that it was faster than a normal TCP
socket; but he was neglecting that the networking hardware handles the
ACK and retransmission transparently, and without needing for the
messages to be handled manually by the application.
This may just be my opinion, but since I was going to be ecamining the
network stack anyways, and typically in a client-server scenario the
ability to maintain a persistent reliable connection where the server
can push important events to the client, that it would be a good
idea. The points about network throttling and QoS are taken, but
wouldn't they also typically affect the UDP stream? Working on MOSES I
have plenty of problems dealing with external users who operate on
restricted networks, and they cannot see traffic aside from 80 and 443
without dealing with their own IT personnel. The fact that it is HTTP
over TCP instead of raw TCP makes no difference once it is on a
non-standard HTTP port.
I agree that it would be more prudent to look at improving the
websocket code and the http server, rather than replace it with a raw
TCP socket, especially given that there are multiple plugins, such as
jsonsimstats, that use the http functionality directly.
I hope that explains my position a little better. I would love to
hear if there are other plans/ideas in the community to address
time-sinks like this one, networking simply appears to us as a good
starting point to increase performance and scalability of the system.
</pre>
</blockquote>
<pre wrap="">
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</pre>
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