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Re: [boehms-gc] Performance results
Le Tue, Jul 25, 2006 at 12:30:04PM -0500, David Nicol écrivait/wrote:
> On 7/24/06, Laurynas Biveinis <laurynas.biveinis@gmail.com> wrote:
>
> >[How is it that setting pointers] to NULL can
> >actually increase peak GC memory usage?
>
> I'll guess that during collection phases, the list of
> collectible structures becomes longer.
>
> GCC is just too huge to try and implement reference counting
> just to see what it would do, right? All managed structures would have
> to include a base class with the count in it and all new references would
> have to be through a macro...
Refcouting is also a nightmare for circular references. I suspect that
GCC gimple trees has some circularities (I might be wrong, not having
dived yet into the code).
A theoritical alternative might be to use a precise copying collector
like Qish. http://starynkevitch.net/Basile/qishintro.html In
practice, this would be impractical (even if the GTY marker could
help) because it requires changing a lot of code.
I've got no explanation regarding zero-ing pointers penalties. Maybe
(just a guess) some cache effect?
Regards
--
Basile STARYNKEVITCH http://starynkevitch.net/Basile/
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