[Haskell-cafe] HEADS UP: finalizer changes coming in GHC 6.10.2

Simon Marlow marlowsd at gmail.com
Wed Jan 14 10:35:33 EST 2009

Johan Tibell wrote:
> On Wed, Jan 14, 2009 at 1:14 PM, Simon Marlow <marlowsd at gmail.com> wrote:
>> By popular demand, GHC 6.10.2 will support finalizers that are actually
>> guaranteed to run, and run promptly.  There aren't any API changes: this
>> happens for finalizers created using newForeignPtr as normal.
> Does this effect GC performance even if you don't use finalizers?
> My knowledge of how finalizers affect GC performance is limited but
> now and then I stumble on some Java article (e.g. [1]) that claims
> that they can slow things down. That's no problem if there's no
> additional cost added to code which doesn't use finalizers.

Yes, having lots of finalizers could affect GC performance, but that hasn't 
changed.  There are things we could do to speed it up, if it became a 
serious bottleneck - for example, we currently look at all the weak 
pointers on every GC, but we could separate them by generation like we do 
for threads.


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