Observable GC

Mike Samuel mikesamuel at gmail.com
Fri Oct 20 14:45:37 UTC 2017

On Fri, Oct 20, 2017 at 10:33 AM, Filip Pizlo <fpizlo at apple.com> wrote:
> For what it’s worth, I have never agreed with this policy. This policy seems
> to be based on feelings not facts.
> I remember implementing real time GCs for Java, which changed GC timing and
> behavior a lot, and having zero problem getting that aspect of the GC to
> work well with existing code. It seems like we are using non-problems to
> make excuses to avoid supporting something useful.
> In fact, WeakMap is more restrictive constraint on GC algo than weak refs or
> finalization or whatever, since it means that a Siebert-style fine-grained
> incremental GC with O(1) increments is off the table.

I'm not familiar with Siebert GCs so I apologize if this is beside
your point.   My recollection of those discussions was that we
rejected weak refs in favor of ephemerons because weak references are
still prone to uncollectible cycles that involve a weakly referenced
object being used as both a key and a value.

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