The Real Time Specification for Java (RTSJ) allows a program to create real-time threads with hard real-time constraints. Real-time threads use region-based memory management to avoid unbounded pauses caused by interference from the garbage collector. The RTSJ uses runtime checks to ensure that deleting a region does not create dangling references and that real-time threads do not access references to objects allocated in the garbage-collected heap. This paper presents a static type system that guarantees that these runtime checks will never fail for well-typed programs. Our type system therefore 1) provides an important safety guarantee for real-time programs and 2) makes it possible to eliminate the runtime checks and their associated overhead.Our system also makes several contributions over previous work on region types. For object-oriented programs, it combines the benefits of region types and ownership types in a unified type system framework. For multithreaded programs, it allows long-lived threads to share objects without using the heap and without memory leaks. For real-time programs, it ensures that real-time threads do not interfere with the garbage collector. Our experience indicates that our type system is sufficiently expressive and requires little programming overhead, and that eliminating the RTSJ runtime checks using a static type system can significantly decrease the execution time of real-time programs.

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Ownership types for safe region-based memory management in real-time Java

This paper reports on our experience with the implementation of the Real-time Specification for Java on the Ovm open source Java virtual machine. We describe the architecture and main design decisions involved in implementing real-time Java on Ovm. We present the first use of Real-time Java in avionics in the context of control software for a ScanEagle Unmanned Aerial Vehicle.

/pdf/a-real-time-java-virtual-machine-with-applications-in-25p49k2dfj.pdf

A real-time Java virtual machine with applications in avionics

Since its official public release, Android has captured the interest from companies, developers and the general audience. From that time up to now, this software platform has been constantly improved either in terms of features or supported hardware and, at the same time, extended to new types of devices different from the originally intended mobile ones. However, there is a feature that has not been explored yet its real-time capabilities. This paper intends to explore this gap and provide a basis for discussion on the suitability of Android in order to be used in Open Real-Time environments. By analysing the software platform, with the main focus on the virtual machine and its underlying operating system environments, we are able to point out its current limitations and, therefore, provide a hint on different perspectives of directions in order to make Android suitable for these environments. It is our position that Android may provide a suitable architecture for real-time embedded systems, but the real-time community should address its limitations in a joint effort at all of the platform layers. Evaluating Android OS for Embedded Real-Time Systems Claudio Maia, Luis Nogueira, Luis Miguel Pinho CISTER Research Centre School of Engineering of the Polytechnic Institute of Porto Porto, Portugal Email:{crrm,lmn,lmp}@isep.ipp.pt Abstract—Since its official public release, Android has captured the interest from companies, developers and the general audience. From that time up to now, this software platform has been constantly improved either in terms of features or supported hardware and, at the same time, extended to new types of devices different from the originally intended mobile ones. However, there is a feature that has not been explored yet its real-time capabilities. This paper intends to explore this gap and provide a basis for discussion on the suitability of Android in order to be used in Open Real-Time environments. By analysing the software platform, with the main focus on the virtual machine and its underlying operating system environments, we are able to point out its current limitations and, therefore, provide a hint on different perspectives of directions in order to make Android suitable for these environments. It is our position that Android may provide a suitable architecture for real-time embedded systems, but the real-time community should address its limitations in a joint effort at all of the platform layers.Since its official public release, Android has captured the interest from companies, developers and the general audience. From that time up to now, this software platform has been constantly improved either in terms of features or supported hardware and, at the same time, extended to new types of devices different from the originally intended mobile ones. However, there is a feature that has not been explored yet its real-time capabilities. This paper intends to explore this gap and provide a basis for discussion on the suitability of Android in order to be used in Open Real-Time environments. By analysing the software platform, with the main focus on the virtual machine and its underlying operating system environments, we are able to point out its current limitations and, therefore, provide a hint on different perspectives of directions in order to make Android suitable for these environments. It is our position that Android may provide a suitable architecture for real-time embedded systems, but the real-time community should address its limitations in a joint effort at all of the platform layers. Keywords-Android, Open Real-Time Systems, Embedded Systems

/pdf/evaluating-android-os-for-embedded-real-time-systems-50w2hw89p6.pdf

Evaluating Android OS for Embedded Real-Time Systems

The paper addresses the issue of improving the performance of memory management for real time Java applications, building upon the Real-Time Specification for Java (RTSJ) from the Real-Time Java Expert Group. In a first step, a thorough analysis of the parameters influencing the performance of memory management together with ways of improvement are presented. The implementation of a memory management solution, which is compliant with the RTSJ and integrating the proposed improvements is then sketched.

Region-based memory management for real-time Java

This paper addresses the issue of improving the performance of memory management for real-time Java applications, building upon the real-time specification for Java (RTSJ) from the Real-Time Java Expert Group. In a first step, a collecting dynamic memory solution including both a real-time garbage collector and region-based memory management, is proposed. A thorough analysis of the parameters influencing the performance of write barriers in memory management, together with ways of improvement are then presented. Finally, the implementation of a memory management solution compliant with the RTSJ and integrating the proposed improvements is sketched.

/pdf/memory-management-for-real-time-java-an-efficient-solution-hrtezcva9p.pdf

Memory Management for Real-Time Java: An Efficient Solution using Hardware Support

Java is a programming language with features not found in traditional languages, such as platform independence and dynamic loading. Because of this, the use of Java is extending and it is beginning to be used in many new environments. In particular, the advantages that Java provides make it a good candidate for distributed, real-time and embedded systems. However, Java presents some problems regarding its use in embedded and real-time environments. In this paper, we examine the state of the art in the development of embedded real-time systems using Java. We analyse the limits that the Java language and its execution environment present in developing real-time and embedded systems, and we present current research in this area that is aimed at solving these limits.

M. Banatre

Papers

Region-based memory management for real-time Java

Java embedded real-time systems: an overview of existing solutions