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Hardware locks for a real-time java chip multiprocessor

CONCURRENCY AND COMPUTATION-PRACTICE & EXPERIENCE 2017年第6期29卷

作者： Strom, Torur Biskopsto Puffitsch, Wolfgang Schoeberl, Martin Tech Univ Denmark Dept Appl Math & Comp Sci DK-2800 Lyngby Denmark

A software locking mechanism commonly protects shared resources for multithreaded applications. This mechanism can, especially in chip-multiprocessor systems, result in a large synchronization overhead. For real-time systems in particular, this overhead increases the worst-case execution time and may void a task set's schedulability. This paper presents 2 hardware locking mechanisms to reduce the worst-case time required to acquire and release synchronization locks. These solutions are implemented for the chip-multiprocessor version of the java Optimized Processor. The 2 hardware locking mechanisms are compared with a software locking solution as well as the original locking system of the processor. The hardware cost and performance are evaluated for all presented locking mechanisms. The performance of the better-performing hardware locks is comparable with that of the original single global lock when contending for the same lock. When several noncontending locks are used, the hardware locks enable true concurrency for critical sections. Benchmarks show that using the hardware locks yields performance ranging from no worse than the original locks to more than twice their best performance. This improvement can allow a larger number of real-time tasks to be reliably scheduled on a multiprocessor real-time platform. Copyright (C) 2016 John Wiley & Sons, Ltd.

关键词： chip multiprocessor hardware locks real-time java real-time systems

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Efficient memory-reference checks for real-time java 03

Efficient memory-reference checks for real-time java

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Proceedings of the 2003 ACM SIGPLAN conference on Language, compiler, and tool for embedded systems

作者： Angelo Corsaro Ron K. Cytron Washington University

ISBN: (纸本)9781581136470

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 *** this paper we present efficient algorithms for managing scoped memories and the checks they impose on programs. Implementations and results published to date require time linear in the depth of scope nesting; our algorithms operate in constant time. We describe our approach and present experiments quantifying the gains in efficiency.

关键词： memory management real-time java scoped memory object oriented languages garbage collection

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Automated discovery of scoped memory regions for real-time java 02

Automated discovery of scoped memory regions for real-time J...

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Proceedings of the 3rd international symposium on Memory management

作者： Morgan Deters Ron K. Cytron Washington University St. Louis MO

ISBN: (纸本)9781581135398

Advances in operating systems and languages have brought the ideal of reasonably-bounded execution time closer to developers who need such assurances for real-time and embedded systems applications. Recently, extensions to the java libraries and virtual machine have been proposed in an emerging standard, which provides for specification of release times, execution costs, and deadlines for a restricted class of threads. To use such features, the code executing in the thread must never reference storage that could be subject to garbage collection. The new standard provides for region-like, stack-allocated areas (scopes) of storage that are ignored by garbage collection and deallocated en masse. It now falls to the developer to adapt ordinary java code to use the real-time java scoped memory ***, it is difficult to determine manually how to map object instantiations to scopes. Moreover, if ordinary java code is modified to effect instantiations in scopes, the resulting code is difficult to read, maintain, and reuse. Static analysis can yield scopes that are correct across all program executions, but such analysis is necessarily conservative in nature. If too many objects appear to live forever under such analysis, then developers cannot rely on static analysis alone to form reasonable *** this paper we present an approach for automatically determining appropriate storage scopes for java objects, based on dynamic analysis---observed object lifetimes and object referencing behavior. While such analysis is perhaps unsafe across all program executions, our analysis can be coupled with static analysis to bracket object lifetimes, with the truth lying somewhere in between. We provide experimental results that show the memory regions discovered by our technique.

关键词： real-time java memory management garbage collection regions trace-based analysis

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Extending the concurrency model of the real-time specification for java

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CONCURRENCY AND COMPUTATION-PRACTICE & EXPERIENCE 2011年第14期23卷 1623-1645页

作者： Basanta-Val, P. Garcia-Valls, M. Estevez-Ayres, I. Univ Carlos III Madrid Dpto Ingn Telemat DREQUIEMI Lab Madrid 28911 Spain

The current RTSJ (real-time Specification for java) threading model is dualized: a programmer has to decide between the high predictability offered by the region-based model and the flexibility offered by the garbage collection. So far, there is no unique type of thread which offers both the high predictability of a non-heap thread and the flexibility of a real-time thread in a single entity. Furthermore, this lack has a serious impact on the programmer who has to deal with new and sometimes non-trivial to use mechanisms, such as specific queues of objects or new types of threads, in order to avoid the priority inversion caused by the garbage collector. In order to tackle the concern properly and provide an improved and more generalized programming model, the authors propose a simple extension to the current threading model named realtimeThread++, in an attempt to introduce more flexibility in the RTSJ concurrency model. The paper describes the extension from several points of view: (i) the programmer, identifying scenarios that may benefit from it significantly;(ii) the real-time java technology perspective, identifying changes required in the current real-time virtual machine to support it;and (iii) the accumulated experience, relating empirical results obtained from a software prototype that supports the extension. Copyright (C) 2010 John Wiley & Sons, Ltd.

关键词： real-time java concurrency models memory management RTSJ

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Distributed java Auction Module on real-time CORBA

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REVISTA IBEROAMERICANA DE AUTOMATICA E INFORMATICA INDUSTRIAL 2012年第4期9卷 406-416页

作者： Basanta-Val, P. Garcia-Valls, M. Morillas-Rodrigo, H. Cano-Romero, J. Univ Carlos III Madrid Dept Ingn Telemat Madrid 28911 Leganes Spain

Using middleware infrastructures that enable communication among different nodes in a system may alleviate aspects related to management and development cost in flexible environments. In that context the article presents an auction architecture with certain real-time requirements that have to be satisfied. The architecture implements a continuous double action (CDA) algorithm for a real-time middleware. The article describes the architecture (actors and goals) and the results obtained by using common-off-the-shelf real-time middleware.

关键词： Action Systems real-time Middleware Industrial informatics RT-CORBA real-time java

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HVM_TP: A time predictable and portable java virtual machine for hard real-time embedded systems 14

HVM<sub>TP</sub>: A time predictable and portable java virtu...

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12th International Workshop on java Technologies for real-time and Embedded Systems (JTRES)

作者： Luckow, Kasper Soe Thomsen, Bent Korsholm, Stephan Erbs Aalborg Univ Dept Comp Sci Aalborg Denmark VIA Univ Coll Horsens Denmark

ISBN: (纸本)9781450328135

We present HVMTP, a time predictable and portable java virtual machine (JVM) implementation with applications in resource-constrained, hard real-time embedded systems, which implements all levels of the safety critical java (SCJ) specification. time predictability is achieved by a combination of time-predictable algorithms, exploiting the programming model of the SCJ profile and harnessing static knowledge of the hosted SCJ system. This paper presents HVMTP in terms of its design and capabilities and demonstrates how a complete timing model of the JVM represented as a network of timed automata can be obtained using the tool TETASARTS(JVM). The timing model readily integrates with the rest of the TETASARTS tool set for temporal verification of SCJ systems. We will also show how a complete timing scheme in terms of safe worst-case execution times and best-case execution times of the java bytecodes can be derived from the model. Furthermore, we take a first look at how to support the new java 8 language feature of Lambda expressions in a SCJ context - we look in particular at how the invokedynamic bytecode can be implemented in a time-predictable way and integrated in HVMTP. Copyright (c) 2016 John Wiley & Sons, Ltd.

关键词： java virtual machine real-time java time predictability model checking

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A Component Framework for java-Based real-time Embedded Systems

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9th International Middleware Conference

作者： Plsek, Ales Loiret, Frederic Merle, Philippe Seinturier, Lionel INRIA Lille Nord Europe CNRS USTL LIFL ADAM Project TeamUMR 8022 F-59650 Villeneuve Dascq France

ISBN: (纸本)9783540898559

The real-time Specification for java (RTS-J) [13] is becoming a popular choice in the world of real-time and embedded programming. However, RTSJ introduces many non-intuitive rules and restrictions which prevent its wide adoption. Moreover, current state-of-the-art frameworks usually fail to alleviate the development process into higher layers of the software development life-cycle. In this paper we extend our philosophy that RTSJ concepts need to be considered at early stages of software development, postulated in our prior work [2], in a framework that provides continuum between the design and implementation process. A component model designed specially for RTSJ serves here as a cornerstone. As the first contribution of this work, we propose a development process where RTSJ concepts are manipulated independently of functional aspects. Second, we mitigate complexities of RTSJ-development by automatically generating execution infrastructure where real-time concerns are transparently managed. We thus allow developers to create systems for variously constrained real-time and embedded environments. Performed benchmarks show that the overhead of the framework is minimal in comparison to manually written object-oriented applications, while providing more extensive functionality. Finally, the framework is designed with the stress on dynamic adaptability of target systems, a property we envisage as a fundamental in an upcoming era of massively developed real-time systems.

关键词： real-time java RTSJ component framework middleware

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Dynamic real-time reconfiguration on a multithreaded java-microcontroller

Dynamic Real-Time reconfiguration on a multithreaded Java-mi...

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7th IEEE International Symposium on Object-Oriented real-time Distributed Computing

作者： Pfeffer, M Ungerer, T Univ Augsburg Inst Comp Sci D-86159 Augsburg Germany

ISBN: (纸本)076952124X

This paper presents an approach for dynamic reconfiguration of an embedded java system in real-time. A class loader executed as a separate thread on a multithreaded microcontroller loads an updated class concurrent to the real-time application. At an uncritical time the application thread switches from the old to the newly updated class. A switching time of 246 clock cycles is determined by a worst-case execution time analysis and checked by measurements on the system. Although this approach is based on a real-time java system it can be adapted to other languages without extensive additional costs.

关键词： real-time java embedded systems real-time kernels and operating systems multithreading dynamic reconfiguration

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A static timing analysis environment using java architecture for safety critical real-time systems 7

A static timing analysis environment using Java architecture...

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7th IEEE International Workshop on Object-Oriented real-time Dependable Systems (WORDS 2002)

作者： Hu, EYS Bernat, G Wellings, A Univ York Dept Comp Sci Real Time Syst Res Grp York YO10 5DD N Yorkshire England

ISBN: (纸本)0769515762

Certainly, in hard real-time systems, it is reasonable to argue that no hard real-time threads should behave in an unpredictable way and that schedulability should be guaranteed before execution. In order to guarantee the timing constraints of portable code for hard real-time applications, a particular static timing analysis is necessary. In this paper, we provide a static timing analysis environment for the development of real-time applications on the java architecture. The major contributions include introducing a novel Extensible Annotations Class (XAC) format to capture portable annotations from the source level, presenting how to integrate XACs with portable Worst-Case Execution time (WCET) analysis, describing how to obtain real-time thread parameters from real-time java's specifications, and demonstrating how static timing analysis using the java architecture can be carried out from portable code.

关键词： java hard real-time systems real-time java Worst-Case Execution time analysis portable WCET analysis

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Introduction to the Special Issue on java Technologies for real-time and Embedded Systems: JTRES 2012

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CONCURRENCY AND COMPUTATION-PRACTICE & EXPERIENCE 2014年第14期26卷 2405-2406页

作者： Teresa Higuera-Toledano, M. Wellings, Andy Univ Complutense Madrid Dept Comp Architecture & Syst Engn E-28040 Madrid Spain Univ York Dept Comp Sci York YO10 5DD N Yorkshire England

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