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A context-aware reflective middleware framework for distributed real-time and embedded systems

JOURNAL OF systems AND SOFTWARE 2011年第2期84卷 205-218页

作者： Liu, Shengpu Cheng, Liang Lehigh Univ Bethlehem PA 18015 USA

Context-aware reflective middleware (CARM), which supports application reconfiguration, has been an appealing technique for building distributed real-time and embedded (DRE) systems as it can adapt their behaviors to changing environments at run time. However, existing CARM frameworks impose dependence restrictions and reconfiguration overhead, which makes the reconfiguration time of these frameworks too long (normally in the range of seconds or more) to satisfy the stringent real-time requirements of DRE systems. To improve the reconfiguration efficiency for supporting DRE systems, we have designed a new CARM framework - MARCHES (Middleware for Adaptive Robust Collaborations across Heterogeneous Environments and systems), which offers an original structure of multiple component chains to reduce local behavior change time and a novel synchronization protocol using active messages to reduce distributed behavior synchronization time. MARCHES uses a layered architecture and provides both component-level and system-level reflection to incorporate standard components, a hierarchical event notification model to evaluate contexts, and a lightweight XML-based script language to describe and manage adaptation policies. The MARCHES framework and supported applications have been implemented on PC and PDA platforms. Based on a novel theoretical model, we have analyzed the reconfiguration efficiency of MARCHES and compared it with those of peer CARM frameworks: MobiPADS and CARISMA. Quantitative empirical results show that the reconfiguration time of MARCHES is reduced from seconds to hundreds of microseconds. Evaluations demonstrate that MARCHES is robust, scalable and generates a small memory footprint, which makes it suitable for supporting ORE systems. (C) 2010 Elsevier Inc. All rights reserved.

关键词： Reflective middleware distributed real-time and embedded systems Reconfiguration Synchronization

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Automated software and hardware evolution analysis for distributed real-time and embedded systems

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OPEN COMPUTER SCIENCE 2011年第1期1卷 36-57页

作者： Dougherty, Brian White, Jules Schmidt, Douglas C. Vanderbilt Univ 1025 16th Ave SSuite 102 Nashville TN 37212 USA Virginia Tech Blacksburg VA 24061 USA

Software evolution is critical to extending the utility and life of distributed real-time and embedded (DRE) systems. Determining the optimal set of software and hardware components to evolve that (1) incorporate cutting-edge technology and (2) satisfy DRE system resource constraints, such as memory, power, and CPU usage is an NP-Hard problem. This article provides four contributions to evolving legacy DRE system configurations. First, we present the Software Evolution Analysis with Resources (SEAR) technique for converting legacy DRE system configurations, external resource availabilities, and candidate replacement components into multiple-choice multidimension knapsack problems (MMKP). Second, we present a formal methodology for assessing the validity of evolved system configurations. Third, we apply heuristic approximation algorithms to determine low-cost, high value evolution paths in polynomial time. Finally, we analyze results of experiments that apply these techniques to determine which technique is most effective for given system parameters. Our results show that constraint solvers can only evolve small system configurations, whereas approximation techniques are needed to evolve larger system configurations.

关键词： distributed real-time and embedded systems system evolution COTS components system configuration MMKP

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distributed priority inheritance for real-time and embedded systems

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10th International Conference on Principles of distributed systems

作者： Sanchez, Cesar Sipma, Henny B. Gill, Christopher D. Manna, Zohar Stanford Univ Dept Comp Sci Stanford CA 94305 USA Washington Univ Dept Comp Sci & Engn St Louis MO 63130 USA

ISBN: (纸本)9783540499909

We study the problem of priority inversion in distributed real-time and embedded systems and propose a solution based on a distributed version of the priority inheritance protocol (PIP). Previous approaches to priority inversions in distributed systems use variations of the priority ceiling protocol (PCP), originally designed for centralized systems as a modification of PIP that also prevents deadlock. PCP, however, requires maintaining a global view of the acquired resources, which in distributed systems leads to high communication overhead. This paper presents a distributed PIP built on top of a deadlock avoidance schema that requires much less communication than PCP. Since the system is already deadlock free and priority inversions can be detected locally, we obtain an efficient dynamic resource allocation system that prevents deadlocks and handles priority inversions.

关键词： priority scheduling deadlock avoidance distributed resource allocation distributed real-time and embedded systems

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Multiparadigm scheduling for distributed real-time embedded computing

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PROCEEDINGS OF THE IEEE 2003年第1期91卷 183-197页

作者： Gill, CD Cytron, RK Schmidt, DC Washington Univ Dept Comp Sci & Engn St Louis MO 63130 USA Univ Calif Irvine Dept Elect & Comp Engn Irvine CA 92697 USA

Increasingly complex requirements, coupled with with tighter economic and organizational constraints, are making it hard to build complex distributed real-time embedded (DRE) systems entirely from scratch. Therefore,, the proportion of DRE systems made up of commercial-off-the-shelf (COTS) hardware and software is increasing significantly. There are, relatively few systematic empirical studies, however, that illustrate how suitable COTS-based hardware and software have become for mission-critical DRE systems. This paper provides the following contributions to the study of real-time quality-of-service (QoS) assurance and performance in COTS-based DRE systems: it presents evidence that flexible configuration of COTS middleware mechanisms, and the operating system (OS) settings they use allows DRE systems to meet critical QoS requirements over a wider range of load and jitter conditions than statically configured systems;it shows that in addition to making critical QoS assurances, noncritical QoS performance can be improved through flexible support for alternative scheduling strategies;and it presents an empirical study of three canonical scheduling strategies;specifically the conditions that predict success of a strategy for a production-quality DRE avionics mission computing system. Our results show that applying a flexible scheduling framework to COTS hardware, OSs, and middleware improves real-time QoS assurance and performance for mission-critical DRE systems.

关键词： distributed real-time and embedded systems dynamic scheduling algorithms and analysis middleware and APIs mission-critical systems quality-of-service (QoS) issues

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Towards highly configurable real-time object request brokers 5

Towards highly configurable real-time object request brokers

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5th IEEE International Symposium on Object-Oriented real-time distributed Computing (ISORC 2002)

作者： Klefstad, R Schmidt, DC O'Ryan, C Univ Calif Irvine Dept Elect & Comp Engn Irvine CA 92697 USA

ISBN: (纸本)0769515584

This paper discusses the software architecture of a real-time CORBA object request broker (ORB) called ZEN, written in real-time Java, which is designed to eliminate common sources of overhead and non-determinism in ORB implementations. We illustrate how ZEN can be configured to select the minimal set of components used by an application. Our experience with ZEN indicates that combining real-time Java with real-time CORBA is a major step forward towards simplifying the development and maintenance of distributed middleware and applications with stringent quality of service requirements.

关键词： distributed real-time and embedded systems real-time CORBA real-time java

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Enhancing real-time CORBA via real-time Java features

Enhancing real-time CORBA via real-time Java features

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24th International Conference on distributed Computing systems

作者： Krishna, AS Schmidt, DC Klefstad, R Vanderbilt Univ Nashville TN 37203 USA

ISBN: (纸本)0769520863

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 real-time 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 CORBA and real-time Java.

关键词： distributed real-time and embedded systems real-time CORBA real-time Java

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