ghci and ghc -threaded broken with pipes & forking

[Ian Lynagh]

On Mon, Mar 05, 2007 at 10:23:53AM -0600, John Goerzen wrote:
> 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.

You can set a default -Nn as described in
    http://www.haskell.org/ghc/docs/latest/html/users_guide/runtime-control.html#rts-hooks
if that helps.


Thanks
Ian