ghci and ghc -threaded broken with pipes & forking

John Goerzen jgoerzen at
Mon Mar 5 11:23:53 EST 2007

On Mon, Mar 05, 2007 at 03:20:05PM +0000, Ian Lynagh wrote:
> > >From reading the docs, it sounds like forkIO keeps everything in a
> > single OS thread/process.  Doesn't this mean that a program that uses
> > forkIO instead of forkOS loses out on SMP machines?
> You can use e.g. +RTS -N2 to use 2 OS threads.

That's rather ugly though, and doesn't "just work".  With other
languages, I could just use OS threads, and let the OS schedule, say, 15
threads across 2 CPUs, or 4 CPUs, or however I may have.

-- John

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