[Caml-list] Why systhreads?

[Lauri Alanko <la@iki.fi>]

Hello.

A simple, fundamental question: why is native-code threading done using
system threads? Why isn't pure user-level scheduling used as with
bytecode?

It seems that all the time incompatibilities and deficiencies in Win32
threads and pthreads cause no end of trouble, for instance they fail to
support the asynchronous exceptions which I yearned for.

Since there is a single heap and threads are run in a strictly
serialized order, system threads don't even give any support for
parallelism. So user-level threading seems like the sensible option. For
instance, the GHC Haskell compiler uses pure user-level threading both
in native code and when interpreted, and it works pretty well. (All
right, there's now talk of adding systhread support, but only for
foreign interface issues.)

I cannot believe that supporting many different system thread interfaces
is easier than managing native-code stacks manually. So could someone
please clarify what the motivation here is?

Thanks.


Lauri Alanko
la@iki.fi
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