Despite its dominance, object-oriented computation has received scant attention from the architecture community. We propose a novel memory architecture that supports objects and garbage collection (GC). Our architecture is co-designed with a Java Virtual Machine to improve the functionality and efficiency of heap memory management. The architecture is based on an address space for objects accessed using object IDs mapped by a translator to physical addresses. To support this, the system includes object-addressed caches, a hardware GC barrier to allow in-cache GC of objects, and an exposed cache structure cooperatively managed by the JVM. These extend a conventional architecture, without compromising compatibility or performance for legacy binaries. Our innovations enable various improvements such as: a novel technique for parallel and concurrent garbage collection, without requiring any global synchronization; an in-cache garbage collector, which never accesses main memory; concurrent compaction of objects; and elimination of most GC store barrier overhead. We compare the behavior of our system against that of a conventional generational garbage collector, both with and without an explicit allocate-incache operation. Explicit allocation eliminates many write misses; our scheme additionally trades L2 misses for in-cache operations, and provides the mapping indirection required for concurrent compaction.
Wright, Seidl, and Wolczko REF present a memory architecture with hardware support for mapping object identifiers to physical addresses, thereby enabling new techniques for parallel and concurrent garbage collection; such an architecture could support compression of pointers as well.
An object-aware memory architecture
Computer Science