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Introduction

OpenSimulator performance is a very complex issue. Performance can be affected by any number of things, including the number of prims on a region, number of regions, number of avatars, network quality between server and viewer, network quality between simulator and grid services, etc.

We can break down a performance discussion into simulator issues (e.g. script performance, region database performance) and grid issues (chiefly scaling services such as asset, inventory, etc to serve more simulators and users).

Simulator

Hardware Requirements

Unfortunately, this is a very difficult question in light of all the factors mentioned in the introduction.

However, we can say that OpenSimulator does not run well when it only has access to a single CPU core - you should regard a dual-core machine as the minimum.

Below are some examples of hardware people use/have used. Please feel free to add to the list, or to add any reports to the performance studies and blog posts section. These are examples to help you in your selection, not necessarily recommendations.

Object Parts ~= # prim

Sensors and Timers are generally more intensive then regular scripts, so please specify quantity of each.

Database

By default, OpenSimulator is configured to use the SQLite database. This is very convenient for an out-of-the-box experience since it requires no configuration. However, it's not designed for heavy usage, so if you build very quickly or have more than a few people on your simulator then you will start to see performance issues.

Therefore, we recommend that you switch to MySQL as soon as possible. This will provide a much better experience but will take a little bit of work to set up.

There is also a database plugin for MSSQL but this is not well maintained between OpenSimulator releases.

Unfortunately, tools for migrating OpenSimulator SQLite data to MySQL are currently limited. Migration is also possible by saving OARs/IARs of your data from sqlite and loading them up once you've reconfigured to use MySQL.

Configuration tweaks

There are a couple of OpenSimulator configuration tweaks that you can do to significantly improve script loading performance in certain situations. These tweaks can be made in your OpenSim.ini config file. These apply to current OpenSimulator development code (0.7.3-dev) and may also apply to 0.7.2, though certainly not any earlier.

Set DeleteScriptsOnStartup = false

[XEngine]
DeleteScriptsOnStartup = false

This means that OpenSimulator will not delete all the existing compiled script DLLs on startup (don't worry, this setting doesn't touch the actual LSL scripts in your region). This will significantly improve startup performance. However, if you upgrade OpenSimulator in place (e.g. you regularly update your installation directly from development code) then you may occasionally see problems if code changes and your previously compiled DLLs can't find their old references.

In this case, you can either set DeleteScriptsOnStartup = true for one restart in order to clean out and recompile script DLLs or you can manually delete the relevant bin/ScriptEngines/<region-uuid>/*.dll.* files, which will force OpenSimulator to recompile them. You could also delete the entire bin/ScriptEngines/<region-uuid> directory but this would lose all persisted script state (which is kept in the <script-item-id>.state files).

Set AppDomainLoading = false

[XEngine]
AppDomainLoading = false

By default, OpenSimulator loads every script DLL into its own AppDomain. If this is set to false, then all scripts are loaded into OpenSimulator's default AppDomain instead.

This will significantly improve script startup times and reduce initial per-script memory overhead.

However, setting this to false will also prevent derezzed script DLLs from being removed from memory (only whole AppDomains can be unloaded). This might cause an OutOfMemory problem over time, as avatars with scripted attachments move in and out of the region. Whether this is a problem for you will depend on factors such as the avatar population of your grid.

In addition, Windows users have reported script loading problems with AppDomainLoading = false, though I (justincc) haven't been able to replicate this with current OpenSimulator code on my WindowsXP machine.

Performance studies and blog posts

These provide some interesting data on the performance limitations of OpenSimulator at various points in time.

• https://lists.berlios.de/pipermail/opensim-users/2010-August/005189.html - Some interesting information from Mr Blue. Physical objects and max avatars are limited by single thread performance in OpenSimulator.
• http://www.sciencesim.com/wiki/doku.php/vwperf/start - Links to ScienceSim performance studies, including some very recent ones.
• Improving Performance - An old page from July 2009 detailing some performance issues on OpenSimulator. Some of these issues are still valid (e.g. ODE issues).
• NHibernate Performance Testing — SQLite and MySQL performance tests with NHibernate.
• LibSecondLife performance problems - Another old page from November 2007 detailing issues with libsecondlife (now called libopenmetaverse).
• Experiences from Operating a 3D Region Server in OSGrid - Part 1
• Experiences from Operating a 3D Region Server in OSGrid - Part 2