Re: GC

[Stefan Monnier]

>> That's not a great advertisement, now is it?
>> I understand how you feel, but the patch is pretty large and is non-working,
>> so it takes a fair bit of effort for anyone to come and help you.
> As far as I know, the only things that are non-working about it are
> weak hash tables (unused, I think)

Actually, they're used in the new compile.el.  I also know they're used in
a few other packages (x-symbol comes to mind), tho compile.el is the only
one I know in Emacs itself.

> and collecting marker chains without crashing.

I.e. all the weak-stuff.  Indeed that's probably the most tricky bit.

> The latter was what I wanted help with since I was fairly sure I was
> missing something fairly obvious and straightforward.

Maybe I can help.  Can you describe what you know of the problem?

>> That's what I would expect as well, but since Emacs's current GC is only
>> conservative w.r.t. stack scanning and has distinct allocation methods for
>> various types of data, Boehm's GC is likely to have a different "performance
>> envelope".
> Yes, like being less likely to thrash my machine collecting...  How
> might the Emacs allocation be better than what you can do with Boehm?

Lots of different ways.  Most/all of them fixable I expect.

>> Right, with USE_LSB_TAG several things might have to be done differently
>> (the off-by-one trick for marker chains springs to mind).
> That isn't a trick I missed that would account for the crashes when I
> tried to collect them, I wonder?  I can't remember enough about it.

No, I was referring to the trick you used to hide the marker-chain from
Boehm's GC tracing routine (thus making it a sort of weak pointer).


        Stefan