Limited reference counting
by Leandro Lucarella on 2008- 09- 03 01:33 (updated on 2008- 09- 03 01:33)- 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.