[pron]

The optimistic locking I mentioned is what we use when RCU is inappropriate (due to multiple pointers).

But just to get the definitions straight: what you call RCU is a copy-on-write combined with a GC algorithm. What would you call a copy-on-write (with no synchronization on the reader's end whatsoever) that uses a general-purpose GC?

Also, I don't understand how hazard pointer GC can be more efficient than a general-purpose GC, given that modern GCs work based on the same principle, only much more refined (e.g. HotSpot creates a stack map containing the location of each reference in every thread's stack instead of a hazard pointer list). Of course compacting collectors (usually young-generation) don't do any reclamation work at all, instead they only work to copy the live objects, so it all comes down to the question what do you have more, live objects or dead objects? But in any case, simple hazard pointer mechanisms seem like a crude, rather old, non-compacting GC technique. I don't see how they can beat a good general-purpose GC.

[sbahra]

Not comparing to HP/PTB/LFRC, just RCU and similar schemes. You're right in that the first class are easy to beat given appropriate workload.

RCU is being conflated, the (Hart) paper I linked to will addresses your questions (sorry phone).