This work is based on Anthony Hannan's original SystemTracer2. It adds a RehashingSystemTracer that allows you to manipulate identity hash values during a trace. See the class comments for SystemTracer2 and RehashingSystemTracer for more details. RECOMMENDED: It is recommended that you load the "Large Collections" package (available on SqueakMap) to get better performance. A trace on my machine that took 9.7 minutes without large collections took only 2.5 minutes with large collections loaded. Large collections are recommended, but not required for SystemTracer2 to work.