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From "Alexey Varlamov" <alexey.v.varla...@gmail.com>
Subject Re: [drlvm] Class unloading support - tested one approach
Date Thu, 09 Nov 2006 15:20:59 GMT
2006/11/9, Robin Garner <robin.garner@anu.edu.au>:
> Etienne Gagnon wrote:
> > Alexey Varlamov wrote:
> >> Sorry if it was already discussed, but I believe this approach also
> >> requires marking vtable bit/byte on each object allocation, unitl the
> >> "unloading" GC pass is strictly stop-the-world full-heap collection.
> >> Robin, did you include this particular overhead too in your
> >> measurements?
> I didn't include it - having established that it's cheap during GC where
> memory bandwidth is at a premium, I kind of took this for granted.
> > My proposal already argued that vtable bit/byte/word marking is
> > unnecessary for "nursery allocations".  You only need to mark the vtable
> > of objects that survive collection and pretenured objects.

I may have missed it, but I only recall you argued that we just need
to collect mature space for the *final unloading* as CL and classes
are unlikely to die young, which I agree. But chances that a live
object of a candidate class appeared in the nursery are higher.
Otherwise I just do not grok how this algorithm can be proven for correctness.

> And this is a persuasive argument.  But I can probably find time to
> measure it tomorrow if you aren't convinced.

That would be very kindly, thank you.

> --
> Robin Garner
> Dept. of Computer Science
> Australian National University

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