John Meacham wrote:
I want to modify jhc to take advantage of mutiple CPUs to help mitigate its prodigious computational requirements and was curious how well ghc compiled programs deal with forking?
my initial plan is that once jhc determines which modules need to be recompiled, it will fork(2) off processes down each pass that can be done in parallel. however, I have no idea what the effect of just calling fork on the ghc runtime will be. both parent and child will continue on compiling code, so it won't be immediatly followed by an exec.
We provide System.Posix.forkProcess, which is a "controlled" version of fork. It probably works ok in the single-threaded runtime, but I'd say it's probably slightly dubious in the threaded runtime especially if you're planning on using it for more than just fork/exec. POSIX puts some tight restrictions on what you can do in the child of a fork in a multi-threaded process (only async-signal-safe operations may be used). Cheers, Simon