Support for Garbage Collection at Every Instruction in a Java^TM Compiler

This paper presents the first multiprocessor garbage collection algorithm with provable bounds on time and space. The algorithm is a real-time shared-memory copying collector. We prove that the algorithm requires at most 2(R(1 + 2(k) + N + 5PD) memory locations, where P is the number of processors, R is the maximum reachable space during a computation (number of locations accessible from the root set), N is the maximum number of reachable objects, D is the maximum depth of any data object, and k is a parameter specifying how many locations are copied each time a location is allocated. Furthermore we show that client threads are never stopped for more than time proportional to k nonblocking machine instructions. The bounds are guaranteed even with arbitrary length arrays. The collector only requires write-barriers (reads are unaffected by the collector), makes few assumptions about the threads that are generating the garbage, and allows them to run mostly asynchronously.