Why do we put GMP allocations on GHC heaps?

[Simon Marlow]

On 24/10/13 09:41, Simon Peyton-Jones wrote:
> | This is true, but I would add that C finalizers are rather more prompt
> | and reliable than Haskell finalizers, since we added special support for
> | them a couple of versions ago.  C finalizers are run directly by the GC
> | rather than in separate threads, and we run all the outstanding ones
> | before the program terminates.
>
> Great.  Is this difference documented?  I couldn't find my way to this info.
>
> I tried Hoogling for "final", and got this link
> http://hackage.haskell.org/package/base-4.6.0.1/docs/Foreign-ForeignPtr.html#v:addForeignPtrFinalizer
> but it is dead.

This seems to be a problem caused by the fact that Foreign.ForeignPtr is 
in both base and haskell2010. Ticket: 
http://ghc.haskell.org/trac/ghc/ticket/8475

> I wonder if it would be worth summarising in the user manual the main facilities offered, with pointers to the Haddock docs that describe them?

http://www.haskell.org/ghc/docs/latest/html/libraries/haskell2010-1.1.1.0/Foreign-ForeignPtr.html

We probably ought to have a bit more there, yes.

Cheers,
Simon




> Simon
>
> | -----Original Message-----
> | From: ghc-devs [mailto:ghc-devs-bounces at haskell.org] On Behalf Of Simon
> | Marlow
> | Sent: 24 October 2013 09:24
> | To: Bryan O'Sullivan; Gergely Risko
> | Cc: ghc-devs at haskell.org
> | Subject: Re: Why do we put GMP allocations on GHC heaps?
> |
> | On 23/10/13 17:08, Bryan O'Sullivan wrote:
> | >
> | > On Wed, Oct 23, 2013 at 4:31 AM, Gergely Risko <gergely at risko.hu
> | > <mailto:gergely at risko.hu>> wrote:
> | >
> | >     I can understand that this may be slower in CPU, but can you
> | please
> | >     elaborate why would it be worse in memory, how the frees wouldn't
> | happen
> | >     in a "timely manner"?  I thought finalisers are called when the
> | >     referencee is GCd, so if we free the mpz in the callback, then
> | where are
> | >     we going wrong?
> | >
> | >
> | > There is no guarantee that finalizers will be called at all, much less
> | > that they will be called in a timely manner. This is a general and
> | > well-known property of all garbage collectors, not something unique to
> | GHC.
> |
> | This is true, but I would add that C finalizers are rather more prompt
> | and reliable than Haskell finalizers, since we added special support for
> | them a couple of versions ago.  C finalizers are run directly by the GC
> | rather than in separate threads, and we run all the outstanding ones
> | before the program terminates.
> |
> | Cheers,
> | 	Simon
> |
> |
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