BINNED REMEMBERED SETS

A garbage collector that performs collection incrementally in accordance with the train algorithm employs remembered sets to keep track of locations where references to objects in respective car sections were written. The remembered sets are implemented as multi-level hash tables. The entries in the top-level hash table are pointers to constituent hash tables in which entries representing the reference locations are placed. When a constituent hash table becomes full, the collector thins it by allocating a new constituent table, transferring some of the previously full table's entries to the new table, and dividing further reference-location-representing entries among them in accordance with a hash function having an expanded range.