Programming with non-heap memory in the real time specification for Java

Abstract

The Real-Time Specification for Java (RTSJ) provides facilities for deterministic, real-time execution in a language that is otherwise subject to variable latencies in memory allocation and garbage collection. A major consequence of these facilities is that the normal Java practice of passing around references to objects in heap memory cannot be used in hard real-time activities. Instead, designers must think carefully about what type of non-heap memory to use and how to transfer data between components without violating RTSJ's memory-area assignment rules. This report explores the issues of programming with non-heap memory from a practitioner's view in designing and programming realtime control loops using a commercially available implementation of the RTSJ.

Enhancing OSGi with real‐time Java support

“…From the point‐of‐view of a programmer, not all these features are simple APIs. Some of them are really (e.g., the programming models for scoped‐memory ) difficult for a programmer and others are really simple (e.g. the use of a real‐time priority inheritance protocol in Java locks or a real‐time garbage collector).…”

“…From the programmer's perspective, the only difference is the name of the class. However, nonheap threads are extremely complex from the point‐of‐view of applications because they have to be coded keeping the assignment and single‐parent rules in mind. The advantage provided by nonheap real‐time threads (and its nonheap memory model) is that they allow programmers to avoid one of the main sources of unpredictability in Java: the garbage collector.…”

“…To date, the integration of real‐time Java and OSGi is still an open issue that requires significant effort to become a real‐time OSGi technology. Significant progress has been made in the definition of admission control techniques for OSGi (). However, these techniques are silent on OSGi's important issues like the definition of general real‐time services, which architects a real‐time framework for OSGi.…”

Eventrons

“…Pizlo et al [20] present a collection of programming idioms and design patterns for using scoped memory. Bollella et al [5] describe the use of restricted memory pools and scoped memory scratchpads as key design patterns in their use of RTSJ to control loops in the Golden Gate/Mission Data System project. They advocate the use of a framework based on these patterns to insulate most programmers from the complexities of directly using RTSJ scoped memory.…”

CD x

“…Driven by the popularity of Java, the availability of development tools, and the wide library support, the Real-Time Specification for Java (RTSJ) [10] is on the rise. It is used in avionics [4], shipboard computing [20], industrial control [17] and music synthesis [5,24].…”