An adaptive, region-based allocator for java

• Authors: Feng Qian;Laurie Hendren
• Venue: Proceedings of the 3rd international symposium on Memory management
• Year: 2002

This paper introduces an adaptive, region-based allocator for Java. The basic idea is to allocate non-escaping objects in local regions, which are allocated and freed in conjunction with their associated stack frames. By releasing memory associated with these stack frames, the burden on the garbage collector is reduced, possibly resulting in fewer collections.The novelty of our approach is that it does not require static escape analysis, programmer annotations, or special type systems. The approach is transparent to the Java programmer and relatively simple to add to an existing JVM. The system starts by assuming that all allocated objects are local to their stack region, and then catches escaping objects via write barriers. When an object is caught escaping, its associated allocation site is marked as a non-local site, so that subsequent allocations will be put directly in the global region. Thus, as execution proceeds, only those allocation sites that are likely to produce non-escaping objects are allocated to their local stack region.The paper presents the overall idea, and then provides details of a specific design and implementation. In particular, we present a region-based allocator and the necessary modifications of the Jikes RVM baseline JIT and a copying collector. Our experimental study evaluates the idea using the SPEC JVM98 benchmarks, plus one other large benchmark. We show that a region-based allocator is a reasonable choice, that overheads can be kept low, and that the adaptive system is successful at finding local regions that contain no escaping objects.