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Limited reference counting

by Leandro Lucarella on 2008- 09- 03 01:33 (updated on 2008- 09- 03 01:33)
tagged limited rc, rc - with 0 comment(s)

Another optimization proposed by the GC book is limiting the reference count field to something smaller than a word. This is just a space optimization, consisting in use something shorter than a word, and marking the cell sticky if an overflow is detected. Sticky cell's reference counters are not updated any more and can be only reclaimed by some sort of tracing collection.

I don't think one word per cell is a big concern for D, but if it is, this optimization is completely doable without extra effort (because I don't see a reference counting implementation in D without some sort of backup tracing collector).

Mental note

Gather some statistics about cell sizes in D, to see if a word is really a big overhead.