Collecting the garbage without blocking the traffic

Java is an increasingly common platform for server-side applications. Such applications are usually long-running, heavily multi-threaded, require very large heaps, executed on multiprocessors, load classes dynamically and make stringent demands of garbage collector performance. Synchronisation of all application threads in order to perform a collection is shown to be a significant bottleneck but current methods fail to solve this issue.

We show how a combination of a new static analysis and novel garbage collector framework can address this issue by allowing independent collection of thread-local heaps. In contrast to previous work, our analysis can classify objects even in the presence of incomplete knowledge; our system is safe in the presence of dynamic class loading; it requires neither synchronisation for nor locks during thread-local collections; and it does not use a write-barrier that may do an unbounded work. Finally, our analysis is sufficiently fast to permit its integration into a high-performance, production-quality virtual machine.