Hello Jason, Saturday, April 17, 2010, 2:00:04 AM, you wrote:
Well, I think Bulat correctly characterized the non-termination aspect. I didn't think the cooperative aspect of threading applied with the threaded RTS, so I'm not 100% sure I believe his characterization, but otherwise it seems like a reasonable explanation.
it's a well known side of ghc green threads implementation. read notes in sources of Control.Concurrent module: The concurrency extension for Haskell is described in the paper /Concurrent Haskell/ http://www.haskell.org/ghc/docs/papers/concurrent-haskell.ps.gz. Concurrency is "lightweight", which means that both thread creation and context switching overheads are extremely low. Scheduling of Haskell threads is done internally in the Haskell runtime system, and doesn't make use of any operating system-supplied thread packages. GHC implements pre-emptive multitasking: the execution of threads are interleaved in a random fashion. More specifically, a thread may be pre-empted whenever it allocates some memory, which unfortunately means that tight loops which do no allocation tend to lock out other threads (this only seems to happen with pathological benchmark-style code, however). -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com