As does perl. You need to declare variables as shared, there is apparently some performance hit, but it's mostly localized to the shared variables, so reasonably manageable. I've actually found it easier to work with than implicit shared data across all threads because you actually need to think about the exposed surface area and how you can minimize it.
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I think Erlang and MS Singularity use this technique to some extent.
http://doi.acm.org/10.1145/1029873.1029875 http://doi.acm.org/10.1145/1146809.1146813 http://research.microsoft.com/apps/pubs/default.aspx?id=6748...
As does perl. You need to declare variables as shared, there is apparently some performance hit, but it's mostly localized to the shared variables, so reasonably manageable. I've actually found it easier to work with than implicit shared data across all threads because you actually need to think about the exposed surface area and how you can minimize it.
People write (http://www.julmar.com/blog/mark/PermaLink,guid,3670d081-0276...) that even .NET itself has a similar kind of GC (partially concurrent, only address fixup stops the world). Unfortunately I can't check how it compares to Singularity.