Re: [Caml-list] Multicore runtime

[Yotam Barnoy <yotambarnoy@gmail.com>]

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Maybe I misunderstood something. Does each domain only have a minor private
heap (ie. copying gc) or do they each also have a major private heap/older
generation (mark and sweep)? If they have an older generation, then a
thread could potentially have a lot of data there, no?

On Wed, Sep 10, 2014 at 6:01 PM, Stephen Dolan <stephen.dolan@cl.cam.ac.uk>
wrote:

> On Tue, Sep 9, 2014 at 4:26 PM, Yotam Barnoy <yotambarnoy@gmail.com>
> wrote:
> > With great care is right :) But seriously, work stealing is a huge
> > undertaking in this model, and may not be feasible at all as far as I can
> > tell. Every private heap object accessed by a thread has to be copied
> either
> > to the shared heap or to the stealer's heap. This is the downside of not
> > having one shared heap for everything. Of course there are huge upsides
> as
> > well, but I don't see how work stealing could work efficiently. The only
> > exception would be for a thread that hasn't started running at all, or
> has
> > allocated very little.
>
> It's implemented, and was demoed last week in the talk you mention.
> Work-stealing is the only reason the silly example program ran faster
> on more cores. Still lots of work to be done, but closer to fait than
> infeasible.
>
> Moving objects from a private to the shared heap is not a big deal.
> This happens anyway during minor garbage collection. Stealing a fiber
> that refers to objects in a private heap essentially involves doing
> some of the minor GC work before the next minor GC would otherwise
> occur.
>
> Stephen
>

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