A Generational and Conservative Copying Collector for Hybrid Objectoriented Languages

A copying collector has two excellent properties: it compacts the heap, and the execution time depends solely on the number of live objects. Use of a copying collector is thought by some to be a more efficient way of managing the heap than explicit freeing of objects. This paper describes a high-performance copying collector for a hybrid object-oriented language. The collector is both conservative and generational. It relies on the overlying compiler to identify most true pointers, and on the underlying operating system to detect pointers to younger generations. The implementation described here uses a modified version of the compiler for a C-based object-oriented language, and the Mach operating system. The performance results have confirmed the author’s expectation: the collector has been faster than explicit freeing.