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<div class="moz-cite-prefix">Hi Doug and Michael,<br>
<br>
Now that I'm also working on the viewer, and prompted by this
thread, I found the code in the viewer that is responsible for the
never-ending stream of AgentUpdate messages. From all I can tell,
it looks like a bug. "Fixing" it results in no behavior changes,
as far as I could see, and the "spam" stops. <br>
<br>
The viewer devs are willing to fix it, at least for opensim.
If/when they do, this will be the single most important
performance optimization for opensim in a while. They are a bit
more reluctant to change the viewer's behavior in the Linden grid.
So I filed a bug report with Linden Lab, to see if that is an
oversight or if they have a good reason for having viewers
constantly sending agent updates. If there's a good reason, it
would be good to know what it is.<br>
<br>
The bug report is here:<br>
<a class="moz-txt-link-freetext" href="https://jira.secondlife.com/browse/BUG-7816">https://jira.secondlife.com/browse/BUG-7816</a><br>
<br>
Hopefully they will look at it and let us all know.<br>
<br>
Best,<br>
Diva<br>
<br>
<br>
On 11/17/2014 6:02 AM, Maxwell, Douglas CIV USARMY ARL (US) wrote:<br>
</div>
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<p>Good Morning Crista, I appreciate the thoughtful response.
Since we have different requirements, it is only natural that
our approaches to the testing methodologies will diverge. It
is easy for us to create a sim that can handle 50 active users
or 100 passive human users. (i.e. 50 people moving about or
100 people seated.) This validates your assertion and we
stand behind it with independent testing. You are welcome to
attend MOSES office hours, should you want to see our grid for
yourself.</p>
<p> </p>
<p>What we need is more than 100 active users in a scene. For
example a platoon of soldiers is 32+ users and if given a
patrol mission, they need to interact with the local
population which could easily be 100 or more people in the
scenario. This is our scalability issue and we require a
different approach to injection of NPCs/bots into the system
to accurately test the simulator modifications.</p>
<p> </p>
<p>As you are aware it is risky to rely on 100's of volunteers
for this testing, further it not feasible or cost effective to
expect hundreds of paid people to participate. We need to
compose an automated way to exercise our designs in a reliable
manner. As I said before, a 90th percentile confidence would
satisfy me.</p>
<p> </p>
<p>We apologize for not being clear earlier, Mike did not mean
to imply the MOSES grid had trouble with 2 users. What we are
saying is that the open simulator is fragile. We can easily
create instabilities and lag with *just* 2 users, meaning the
grid is susceptible to even minor perturbations. </p>
<p> </p>
<p>I believe we have parallel interests here in that we wish to
make the simulator usable with 10x more users than currently
possible (hundreds instead of just 10's). Our development
roadmap for the next 11 months includes changes to data
transport, physics, and possibly databases. We will continue
to engage this mailing list and offer our code back to the
community to abide by all relevant open source licensing
terms. This work is performed using a public GitHub site:
<a moz-do-not-send="true" href="https://github.com/M-O-S-E-S">https://github.com/M-O-S-E-S</a></p>
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<p> </p>
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<div id="divRpF596374" style="DIRECTION: ltr"><font
color="#000000" face="Tahoma" size="2"><b>From:</b>
<a class="moz-txt-link-abbreviated" href="mailto:opensim-dev-bounces@opensimulator.org">opensim-dev-bounces@opensimulator.org</a>
[<a class="moz-txt-link-abbreviated" href="mailto:opensim-dev-bounces@opensimulator.org">opensim-dev-bounces@opensimulator.org</a>] on behalf of Diva
Canto [<a class="moz-txt-link-abbreviated" href="mailto:diva@metaverseink.com">diva@metaverseink.com</a>]<br>
<b>Sent:</b> Friday, November 14, 2014 12:03 PM<br>
<b>To:</b> <a class="moz-txt-link-abbreviated" href="mailto:opensim-dev@opensimulator.org">opensim-dev@opensimulator.org</a><br>
<b>Subject:</b> Re: [Opensim-dev] Modifying the networking
stack (UNCLASSIFIED)<br>
</font><br>
</div>
<div>
<div class="moz-cite-prefix">On 11/14/2014 8:46 AM, Maxwell,
Douglas CIV USARMY ARL (US) wrote:<br>
</div>
<blockquote type="cite">
<pre>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 type="cite">
<pre>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 type="cite">
<pre>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 moz-do-not-send="true" class="moz-txt-link-abbreviated" href="https://web-mont05.mail.mil/owa/UrlBlockedError.aspx" target="_blank">opensim-dev-bounces@opensimulator.org</a>
[<a moz-do-not-send="true" class="moz-txt-link-freetext" href="https://web-mont05.mail.mil/owa/UrlBlockedError.aspx" target="_blank">mailto:opensim-dev-bounces@opensimulator.org</a>] On Behalf Of Diva Canto
Sent: Friday, November 14, 2014 11:05 AM
To: <a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="https://web-mont05.mail.mil/owa/UrlBlockedError.aspx" target="_blank">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>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>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 moz-do-not-send="true" class="moz-txt-link-freetext" href="https://web-mont05.mail.mil/owa/UrlBlockedError.aspx" target="_blank">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>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>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>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>_______________________________________________
Opensim-dev mailing list
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Caveats: NONE
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