Default options for -threaded

[Carter Schonwald]

Yup! Let’s do it. Efficient io and compute during ffi computation sound
good to me

On Fri, Jan 4, 2019 at 10:22 AM Matthew Pickering <
matthewtpickering at gmail.com> wrote:

> Two years seems a good amount of time for any objectors.
>
> https://ghc.haskell.org/trac/ghc/ticket/16126#ticket
>
> On Fri, Oct 21, 2016 at 5:35 PM Simon Marlow <marlowsd at gmail.com> wrote:
> >
> > On 8 October 2016 at 17:55, Ben Gamari <ben at well-typed.com> wrote:
> >>
> >> lonetiger at gmail.com writes:
> >>
> >> > Hi All,
> >> >
> >> > A user on https://ghc.haskell.org/trac/ghc/ticket/11054 has asked why
> >> > -N -qa isn’t the default for -threaded.
> >> >
> >> I'm not sure that scheduling on all of the cores on the user's machine
> by
> >> default is a good idea, especially given that our users have
> >> learned to expect the existing default. Enabling affinity by default
> >> seems reasonable if we have evidence that it helps the majority of
> >> applications, but we would first need to introduce an additional
> >> flag to disable it.
> >
> >
> > Affinity is almost always a bad idea in my experience.
> >
> >>
> >> In general I think -N1 is a reasonable default as it acknowledges the
> >> fact that deploying parallelism is not something that can be done
> >> blindly in many (most?) applications. To make effective use of
> >> parallelism the user needs to understand their hardware, their
> >> application, and its interaction with the runtime system and configure
> >> the RTS appropriately.
> >>
> >
> > Agree on keeping -N1.
> >
> > Related to this, I think it's about time we made -threaded the default.
> We could add a -single-threaded option to get back the old behaviour.
> >
> > There is a small overhead to using -threaded, but -threaded is also
> required to make a lot of things work (e.g. waitForProcess in a
> multithreaded program, not to mention parallelism).
> >
> > Anyone interested in doing this?
> >
> > Cheers
> > Simon
> >
> >
> >>
> >> Of course, this is just my two-cents.
> >>
> >> Cheers,
> >>
> >> - Ben
> >>
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