Real-Time Garbage Collection in Multi-Threaded Systems on a Single Processor

We show the difficulties that arise for the implementation of a real-time garbage collector in a multi-threaded system. A mechanism for synchronization between threads and the garbage collector activities is proposed for a single processor system. It is shown how this mechanism can be used to maintain exact information on roots, to implement efficient write-barriers, to do incremental or even constanttime root-scanning and to guarantee short pre-emption time of garbage collector activity. Special aspects of an implementation for Java that are affected by this mechanism will also be addressed. Finally, experimental data is presented to show that the proposed mechanisms can efficiently be used in real programs.