> Self healing is a unique capability that, as far as we know, the Azul collector is the only one to do, and it can only be done with a read barrier.

The Metronome GC from IBM Research (http://www.research.ibm.com/people/d/dfb/papers/Bacon05High....) also uses a read-barrier to fix up pointers to objects which have moved.

Although, I don't think it does marking in the read barrier.