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Linden Labs Help Mono Fix Leaks


The Second Life developers at Linden Labs, working in conjunction with the Mono team, have been able to fix several memory leaks in Mono, significantly improving the runtime performance and stability of the platform.

Since 2005, Linden Research has been considering Mono as the runtime for their scripting engine. The original plan called for compiling the Linden Scripting Language into CIL. CIL or Common Intermediate Language is an assembly-like language that all higher level programming languages like C# and VB need to be compiled to prior to being run by Microsoft's CLR or the Mono runtime.

Presumably Mono was chosen for its cross-platform capabilities. Mono, which is supported by Novell, is currently the most complete cross-platform implementation of the .NET framework available for commercial projects.

At the LANG.Net 2006 Symposium, Babbage Linden presented their work in integrating LSL. Babbage reports ( that the conference went over quite well.

I was initially concerned that the collection of hacks I presented for embedding Mono in SL might appall people, but the consensus seemed to be that they were neat hacks and they generated a lot of discussion about potential future enhancements to the CLR. A lot of discussion at the conference was about supporting dynamic languages like Ruby which, like Second Life, would benefit immensely from support for continuations in the CLI. Hopefully we’ll see them in the future.

During the presentation, Babbage noticed that the simulator memory was steadily growing. Concerned, he first examined his own code for memory leaks. Not finding any, he turned to the Mono runtime itself.

Using Valgrind's memcheck and massif tools, Babbage was able to collect the information needed by Mono's Paolo Molaro to correct the issue. Early results show that Mono is no longer growing in size, indicating that the performance robbing flaws have been corrected.

Babbage concludes with

With this development, the work on Mono takes another step forwards. We’re currently working on moving script compilation to our new web services platform and once that’s done I can wire in the LSL to Mono compiler, bytecode injector and verifier as web services and then the main pieces of the work on Mono will be done.


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