Pretenuring in Java by object lifetime and reference density using scratch-pad memory

Abstract

Java has become a popular paradigm in software development. It is widely used in embedded systems and network computing because of its excellent robustness, modularity and security. Its built-in garbage collection automatically reclaims unused memory space. Current generational garbage collector works well with programs containing massive short-lived objects. However, the existence of hot-mature (i.e. frequently-accessed and long-lived) objects inhibits object reclamation. In this study, we present two approaches to exploit the locality for these objects. Firstly, we employ an on-chip scratchpad memory in memory hierarchy to preserve young and hot-mature objects. This reduces data accessing cycle for Java execution by 49% to 224%. Secondly, we introduce a pretenuring technique to segregate objects into separated memory regions based on the object lifetimes and reference densities, which reduces the amount of object copying during garbage collections by 26% to 74%. Keywords: dynamic memory management, garbage collection, pretenuring, scratchpad memory, Java.