Hardware concurrent garbage collection for short-lived objects in an object-oriented processor

jHISC is an object-oriented processor for embedded system aiming at accelerating Java execution by hardware approach. Garbage collection is one of the critical tasks in a Java Virtual Machine. We have conduct a study of dynamic object allocation and garbage collection behavior of Java program based on SPECjvm 98 benchmark suite and MIDP applications for mobile phone. Life, size, and reference count distribution of Java objects are measured. The study discovered that most Java objects die very young, small in size and have small number reference count. Reference counting object cache with hardware write barrier and object allocator is proposed to provide the hardware concurrent garbage collection for small size objects in jHISC. Hardware support on write barriergreatly reduces the overhead to perform the reference count update. The reference-count collector reclaims the memory occupied by an object immediately afler it becomes garbage. The allocator provides a constant time object allocation. According the performance evaluation, over halfof Java object can be garbage collected by the object cache that make its unnecessary for these object to copy to the main memory.