Abstract Implementing a concurrent programming language such as Java by means of a translator to an existing language is attractive as it provides portability over all platforms supported by the host language and reduces development time—as many low‐level tasks can be delegated to the host compiler. The C and C++ programming languages are popular choices for many language implementations due to the availability of efficient compilers on a wide range of platforms. For garbage‐collected languages, however, they are not a perfect match as no support is provided for accurately discovering pointers to heap‐allocated data on thread stacks. We evaluate several previously published techniques and propose a new mechanism, lazy pointer stacks, for performing accurate garbage collection in such uncooperative environments. We implemented the new technique in the Ovm Java virtual machine with our own Java‐to‐C/C++ compiler using GCC as a back‐end compiler. Our extensive experimental results confirm that lazy pointer stacks outperform existing approaches: we provide a speedup of 4.5% over Henderson's accurate collector with a 17% increase in code size. Accurate collection is essential in the context of real‐time systems, we thus validate our approach with the implementation of a real‐time concurrent garbage collection algorithm. Copyright © 2009 John Wiley & Sons, Ltd.

Abstract The standard dispatching mechanisms built into programming languages sometimes fail to satisfy the needs of the programmer. In the case of Java, the need for more flexibility has led to the development of a number of tools, including visitors and multi‐method extensions, that each add some particular functionality, but lack the generality necessary to support user‐defined dispatching mechanisms. In this paper we advocate a more modular approach to dispatching, and we present a tool, PolyD, that allows the programmer to design custom dispatching strategies and to parametrize many aspects of the dispatching process. PolyD exhibits excellent performance and compares well against existing tools. Copyright © 2007 John Wiley & Sons, Ltd.

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.

The progress towards programming methodologies that simplify the work of the programmer involves automating, whenever possible, activities that are secondary to the main task of designing algorithms and developing applications. Automatic memory management, using garbage collection, and automatic persistence, using checkpointing, are both examples of mechanisms that operate behind the scenes, simplifying the work of the programmer. Implementing such mechanisms in the presence of real-time constraints, however, is particularly difficult.In this paper we review the behavior of traditional copy-on-write implementations of checkpointing in the context of real-time systems, and we show how such implementations may, in pathological cases, seriously impair the ability of the user code to meet its deadlines. We discuss the source of the problem, supply benchmarks, and discuss possible remedies. We subsequently propose a novel approach that does not rely on copy-on-write and that, while more expensive in terms of CPU time overhead, is unaffected by pathological user code. We also describe our implementation of the proposed solution, based on the Ovm RTSJ Java Virtual Machine, and we discuss our experimental results.

The standard dispatching mechanisms built into programming languages are sometimes inadequate to the needs of the programmer. In the case of Java, the need for more flexibility has led to the development of a number of tools, including visitors and multi-method extensions, that each add some particular functionality, but lack the generality necessary to support user-defined dispatching mechanisms. In this paper we advocate a more modular approach to dispatching, and we present a tool, PolyD, that allows the programmer to design custom dispatching strategies and to parametrize many aspects of the dispatching process. PolyD exhibits excellent performance and compares well against existing tools.

We present a new concurrency control abstraction for real-time systems called preemptible atomic regions (PARs). PARs a transactional mechanism that improves upon lock-based mutual exclusion in several ways. First, and foremost, PARs provide strong correctness guarantees. Any sequence of operations declared atomic will not suffer interference from other threads, even in the presence of programmer errors. In spite of this, PARs can be preempted by high priority tasks; this is essential to the minimization of blocking times. We have implemented PARs in a uniprocessor real-time Java virtual machine and evaluated their utility on a number of programs. The results suggest that programs that use PARs, depending on their semantics, can run faster and experience less jitter than those that use locks