A High Performance Garbage Collector for Java

Abstract

Parallel, multithreaded Java applications such as web servers, database servers, and scientific applications are becoming increasingly prevalent. For these applications, the dynamic memory manager (i.e., the garbage collector) is often a bottleneck that limits program performance and processor utilization on multiprocessor systems. Traditional garbage collectors suffer from long garbage collection pauses (stop-the-world mark-sweep algorithm) or inability of collecting cyclic garbage (reference counting approach). Generational garbage collection, however, is based only on the weak generational hypothesis that most objects die young. In this paper, a new multithreaded concurrent generational garbage collector (MCGC) based on mark-sweep with the assistance of reference counting is proposed. The MCGC can take advantage of multiple CPUs in an SMP system and the merits of light weight processes. Furthermore, the long garbage collection pause can be reduced and the garbage collection efficiency can be enhanced. To simulate the real-world workload (i.e., the SPECjvm98 benchmark), we have implemented the proposed scheme into the Kaffe JVM version 1.0.6 running on Linux RedHat 6.2. Measurement results indicate that the MCGC improves the garbage collection pause time up to 96.75% over the traditional stop-the-world mark-sweep garbage collector. Moreover, the MCGC receives minimal time and space penalties as shown in the report of the total execution time, the memory footprint and the sticky reference count rate.