[Haskell-cafe] Re: GHC: compile using multiple cores?

Andrea Vezzosi sanzhiyan at gmail.com
Thu Apr 9 19:08:46 EDT 2009

The main bottleneck right now is that each ghc process has to read the
package.conf, which afaiu is done with Read and it's awfully slow,
especially if you have many packages installed.
I've started seeing total time improvements when approaching ~300% CPU
usage and only the extralibs installed.

On Thu, Apr 9, 2009 at 5:51 PM, Neil Mitchell <ndmitchell at gmail.com> wrote:
>> Not with cabal, with GHC, yes: assuming you have enough modules. Use ghc
>> -M to dump a makefile, and then make -j20 (or whatever you have)
> There is a performance penalty to running ghc on separate files vs
> --make. If your number of core's is limited --make may be better. I'd
> love someone to figure out what the cross over point is :-)
> As a related question, how does GHC implement -j3? For my programs, if
> I want to run in parallel, I have to type +RTS -N3. Can I use the same
> trick as GHC?
> Thanks
> Neil
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