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21
Ownership Types for Safe Region-Based Memory Management in Real-Time Java
- IN PROGRAMMING LANGUAGE DESIGN AND IMPLEMENTATION (PLDI
, 2003
"... 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 dele ..."
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Cited by 104 (7 self)
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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 suciently 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.
SafeJava: A Unified Type System for Safe Programming
, 2004
"... Making software reliable is one of the most important technological challenges facing our society today. This thesis presents a new type system that addresses this problem by statically preventing several important classes of programming errors. If a program type checks, we guarantee at compile time ..."
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Cited by 60 (1 self)
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Making software reliable is one of the most important technological challenges facing our society today. This thesis presents a new type system that addresses this problem by statically preventing several important classes of programming errors. If a program type checks, we guarantee at compile time that the program does not contain any of those errors. We designed our type system in the context of a Java-like object-oriented language; we call the resulting system SafeJava. The SafeJava type system offers significant software engineering benefits. Specifically, it provides a statically enforceable way of specifying object encapsulation and enables local reasoning about program correctness; it combines effects clauses with encapsulation to enable modular checking of methods in the presence of subtyping; it statically prevents data races and deadlocks in multithreaded programs, which are known to be some of the most difficult programming errors to detect, reproduce, and
Enhancing Real-Time CORBA via Real-Time Java Features
- in 24th International Conference on Distributed Computing Systems (ICDCS 2004), Hachioji
, 2004
"... Abstract — End-to-end middleware predictability is essential to support quality of service (QoS) capabilities needed by distributed real-time and embedded (DRE) applications. Real-time CORBA is a middleware standard that allows DRE applications to allocate, schedule, and control the QoS of CPU, memo ..."
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Cited by 20 (0 self)
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Abstract — End-to-end middleware predictability is essential to support quality of service (QoS) capabilities needed by distributed real-time and embedded (DRE) applications. Real-time CORBA is a middleware standard that allows DRE applications to allocate, schedule, and control the QoS of CPU, memory, and networking resources. Existing Real-time CORBA solutions are implemented in C++, which is generally more complicated and error-prone to program than Java. The Real-Time Specification for Java (RTSJ) provides extensions that enable Java to be used for developing DRE systems. Real-time CORBA does not currently leverage key RTSJ features, such as scoped memory and real-time threads. Thus, integration of Real-Time CORBA and RTSJ is essential to ensure the predictability required for Java-based DRE applications. This paper provides the following contributions to the study of middleware for DRE applications. First we analyze the architecture of ZEN, our implementation of Real-time CORBA, identifying sources for the application of RTSJ features. Second, we describe how RTSJ features, such as scoped memory and real-time threads, can be associated with key ORB components to enhance the predictability of DRE applications using Realtime CORBA and the RTSJ. Third, we perform preliminary qualitative and quantitative analysis of predictability enhancements arising from our application of RTSJ features. Our results show that use of RTSJ features can considerably improve the predictability of DRE applications written using Real-time
Scoped types and aspects for real-time Java memory management
- Realtime Systems Journal
, 2007
"... Abstract. Real-time systems are notoriously difficult to design and implement, and, as many real-time problems are safety-critical, their solutions must be reliable as well as efficient and correct. While higher-level programming models (such as the Real-Time Specification for Java) permit real-time ..."
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Cited by 18 (7 self)
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Abstract. Real-time systems are notoriously difficult to design and implement, and, as many real-time problems are safety-critical, their solutions must be reliable as well as efficient and correct. While higher-level programming models (such as the Real-Time Specification for Java) permit real-time programmers to use language features that most programmers take for granted (objects, type checking, dynamic dispatch, and memory safety) the compromises required for real-time execution, especially concerning memory allocation, can create as many problems as they solve. This paper presents Scoped Types and Aspects for Real-Time Systems (STARS) a novel programming model for real-time systems. Scoped Types give programmers a clear model of their programs ’ memory use, and, being statically checkable, prevent the run-time memory errors that bedevil the RTSJ. Adopting the integrated Scoped Types and Aspects approach can significantly improve both the quality and performance of a real-time Java systems, resulting in simpler systems that are reliable, efficient, and correct. 1
Efficient Memory-Reference Checks for Real-time Java
- In LCTES 2003
, 2003
"... The scoped-memory feature is central to the Real-Time Specification for Java. It allows greater control over memory management, in particular the deallocation of objects without the use of a garbage collector. To preserve the safety of storage references associated with Java### since its inception, ..."
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Cited by 12 (4 self)
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The scoped-memory feature is central to the Real-Time Specification for Java. It allows greater control over memory management, in particular the deallocation of objects without the use of a garbage collector. To preserve the safety of storage references associated with Java### since its inception, the use of scoped memory is constrained by a set of rules in the specification. While a program's adherence to the rules can be partially checked at compile-time, undecidability issues imply that some---perhaps, many---checks may be required at run-time. Poor implementations of those run-time checks could adversely affect overall performance and predictability, the latter being a founding principle of the specification.
JOP: A java optimized processor
- In Workshop on Java Technologies for Real-Time and Embedded Systems (JTRES 2003
, 2003
"... Abstract. Java is still not a common language for embedded systems. It posses language features, like thread support, that can improve embedded system development, but common implementations as interpreter or just-in-time compiler are not practical. JOP is a hardware implementation of the Java Virtu ..."
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Cited by 11 (2 self)
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Abstract. Java is still not a common language for embedded systems. It posses language features, like thread support, that can improve embedded system development, but common implementations as interpreter or just-in-time compiler are not practical. JOP is a hardware implementation of the Java Virtual Machine with focus on real-time applications. This paper describes the architecture of JOP and proposes a simple real-time extension of Java for JOP. First application in an industrial system showed that JOP is one way to use Java in the embedded world. 1
Towards Predictable Real-time Java Object Request Brokers
- in Proceedings of the 9th Real-time/Embedded Technology and Applications Symposium (RTAS
, 2003
"... Distributed real-time and embedded (DRE) applications often possess stringent quality of service (QoS) requirements. Designing middleware for DRE applications poses several challenges to object request broker (ORB) developers. This paper provides the following contributions to the study of middlewar ..."
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Cited by 6 (3 self)
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Distributed real-time and embedded (DRE) applications often possess stringent quality of service (QoS) requirements. Designing middleware for DRE applications poses several challenges to object request broker (ORB) developers. This paper provides the following contributions to the study of middleware for DRE applications. First, we outline the challenges present in one of the principal ORB components -- the portable object adapter (POA) -- focusing on predictable and scalable demultiplexing. Second, we describe how these challenges are addressed in ZEN, which is an implementation of Real-time CORBA that runs atop jRate, an ahead-of-time compiler that implements most of the RealTime Specification for Java (RTSJ). Third, we qualitatively and quantitatively compare ZEN's demultiplexing strategies with those of other popular Java ORBs, including JacORB, Sun JDK ORB, and ORBacus. Our results show that ZEN and jRate incorporate the strategies necessary to enable predictability using standards-based middleware and also provide a baseline for what can be achieved by combining Real-time CORBA and RTSJ.
The Design and Performance of Real-time Java Middleware
"... Over 90 percent of all microprocessors are now used for real-time and embedded applications. Since the behavior of these applications is often constrained by the physical world, it is important to devise higher-level languages and middleware that meet conventional functional requirements and dependa ..."
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Cited by 5 (1 self)
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Over 90 percent of all microprocessors are now used for real-time and embedded applications. Since the behavior of these applications is often constrained by the physical world, it is important to devise higher-level languages and middleware that meet conventional functional requirements and dependably and productively enforce real-time constraints.
Real-time android with rtdroid
- In MobiSys
, 2014
"... This paper presents RTDroid, a variant of Android that provides predictability to Android applications. Although there has been much interest in adopting Android in real-time contexts, surpris-ingly little work has been done to examine the suitability of An-droid for real-time systems. Existing work ..."
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Cited by 2 (0 self)
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This paper presents RTDroid, a variant of Android that provides predictability to Android applications. Although there has been much interest in adopting Android in real-time contexts, surpris-ingly little work has been done to examine the suitability of An-droid for real-time systems. Existing work only provides solutions to traditional problems, including real-time garbage collection at the virtual machine layer and kernel-level real-time scheduling and resource management. While it is critical to address these issues, it is by no means sufficient. After all, Android is a vast system that is more than a Java virtual machine and a kernel. Thus, this paper goes beyond existing work and examines the internals of Android. We discuss the implications and challenges of adapting Android constructs and core system services for real-time and present a solution for each. Our system is unique in that it redesigns Android’s internal components, replaces Android’s Java VM (Dalvik) with a real-time VM, and leverages off-the-shelf real-time OSes. We demonstrate the feasibility and predictability of our solution by evaluating it on three different platforms—an x86 PC, a LEON3 embedded board, and a Nexus S smartphone. The evaluation results show that our design can successfully provide predictability to Android applications, even under heavy load. Categories and Subject Descriptors
Fault tolerance with real-time java
- In WPDRTS’06 (in proceedings of the 20st IEEE International Parallel & Distributed Processing Symposium), page 172, Rhodes Island
, 2006
"... After having drawn up a state of the art on the theoretical feasibility of a system of periodic tasks scheduled by a preemptive algorithm at fixed priorities, we show in this article that temporal faults can occur all the same within a theoretically feasible system, that these faults can lead to a f ..."
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Cited by 1 (1 self)
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After having drawn up a state of the art on the theoretical feasibility of a system of periodic tasks scheduled by a preemptive algorithm at fixed priorities, we show in this article that temporal faults can occur all the same within a theoretically feasible system, that these faults can lead to a failure of the system and that we can use the data calculated during control of admission to install detectors of faults and to define a factor of tolerance. We show then the results obtained on a system of periodic tasks coded with Java Real-Time and carried out with the virtual machine jRate. These results show that the installation of the detectors and the tolerance to the faults makes an improvement of the behavior of the system in the presence of faults. 1.
