Name-Based Write Barriers in Real-Time Java

Abstract

From a real-time perspective, the GC introduces unpredictable pauses that are not tolerated by real-time tasks. Real-time collectors eliminate this problem but introduce a high overhead. Another approach is to use memory regions (MR) within which allocation and deallocation are customized. This facility is supported by the memory model of the Real-Time Specification for Java (RTSJ). RTSJ imposes strict access rules and assignment rules to avoid both delays of critical tasks for the GC and dangling inter-region references, which results in an unfamiliar programming model. The guidelines given by RTSJ to implement the assignment rules also increase the program complexity. This paper provides an indepth analytical investigation of the dynamic checks required to maintain the safety of a RTSJ implementation, and propose a simplification of the algorithms managing memory regions which requires some changes on the RTSJ memory management rules.