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IEEE International Conference on Embedded and real-time computing Systems and Applications (RTCSA)

作者： Jinho Kim K.G. Shin Department of Computer Science Kangwon University Chuncheon South Korea Real-Time Computing Laboratory Department of EECS University of Michigan Ann Arbor MI USA

real-time process control systems require hard real-time data logging tasks to access all of the data sampled from plants and monitoring tasks to analyze the status of the plants. This paper presents an integrated scheduling scheme for hard real-time data logging tasks and soft real-time monitoring tasks, both types of which require disk I/Os. Conventional disk scheduling policies like Shortest-Seek-time-First (SSTF), SCAN, and C-SCAN, reorder disk I/O requests to minimize the disk head's seek time, thus making it very difficult to guarantee the timely completion of the tasks requiring disk I/Os. Our scheduling scheme provides timeliness guarantees by serializing all disk I/O requests of these tasks based on their priorities. Because it doesn't require any special-purpose real-time disk scheduling algorithm, the proposed scheme can be implemented on top of general-purpose operating systems like UNIX.

关键词： real time systems Process control Control systems Job shop scheduling Processor scheduling computerized monitoring Scheduling algorithm Automatic control History Sampling methods

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Testing of fault-tolerant and real-time distributed systems via protocol fault injection

Testing of fault-tolerant and real-time distributed systems ...

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International Symposium on Fault-Tolerant computing (FTCS)

作者： S. Dawson F. Jahanian T. Mitton Teck-Lee Tung Real-Time Computing Laboratory Electrical Engineering and Computer Science Department University of Michigan Ann Arbor MI USA Electrical Engineering and Computer Science Department University of Michigan Ann Arbor MI USA

As software for distributed systems becomes more complex, ensuring that a system meets its prescribed specification is a growing challenge that confronts software developers. This is particularly important for distributed applications with strict dependability and timeliness constraints. This paper reports on ORCHESTRA, a portable fault injection environment for testing implementations of distributed protocols. This tool is based on a simple yet powerful framework called script-driven probing and fault injection, for the evaluation and validation of the fault-tolerance and timing characteristics of distributed protocols. The tool, which was initially developed on the real-time Mach operating system and later ported to other platforms including Solaris and SunOS, has been used to conduct extensive experiments on several protocol implementations. This paper describes the design and implementation of the fault injection tool focusing on architectural features to support portability, minimizing intrusiveness on target protocols, and explicit support for testing real-time systems. The paper also describes the experimental evaluation of two protocol implementations: a real-time audio-conferencing application on real-time Mach, and a distributed group membership service on the Sun Solaris operating system.

关键词： System testing Fault tolerant systems real time systems Protocols Operating systems Software systems Application software Fault tolerance Timing Sun

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Architecture and language support for fault-tolerance in complex real-time systems

Architecture and language support for fault-tolerance in com...

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IEEE International Conference on Engineering of Complex computer Systems

作者： A.K. Ganesh T.J. Marlowe A.D. Stoyenko M.F. Younis J. Salinas Real-Time Computing Laboratory Department of Computer & Information Science New Jersey Institute of Technology Newark NJ USA Department of Mathematics and Computer Science Seton Hall University South Orange NJ USA Naval Undersea Warfare Center New London CT USA

The overhead of the general checkpointing approach is infeasible for distributed real-time systems where timing is critical. We present a new compiler based approach which classifies data, and minimizes the data needed for checkpointing using static data flow analysis and language support. Our approach provides static guarantees of timeliness while checkpointing, and explores timely recovery for real-time systems. We outline our approach and discuss the necessary architecture and language support needed to make this feasible.

关键词： Fault tolerant systems real time systems Checkpointing Timing Distributed computing Military computing computer errors Certification computer architecture Laboratories

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Message transmission with timing constraints in ring networks

Message transmission with timing constraints in ring network...

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real-time Systems Symposium (RTSS)

作者： Ching-Chih Han K.G. Shin Department of Electrical Engineering Ohio State Uinversity Columbus OH USA Real-Time Computing Laboratory Department of Elect. Engineering and Computer Science University of Michigan Ann Arbor MI USA

We consider the message transmission problem in unidirectional slotted ring networks. We consider two operation modes: 1) the evacuation mode, in which all messages arrive before system initialization and no new message arrives during system operation; and 2) the continuation mode, in which new messages may arrive after system initialization. We study the performance of several message scheduling policies with respect to three performance measures: meeting all message deadlines, minimizing the maximum delay or the total length of busy periods, and minimizing the average delay. We show that the least-slack-time-first (LSF) scheduling policy is optimal in evacuation mode operation with respect to meeting all message deadlines, while no optimal scheduling policy can possibly exist for continuation mode operation. For the other two performance measures, we show that in the case when messages may be of variable lengths: 1) the farthest-destination-first (FDF) policy is optimal in terms of minimizing the maximum delay and minimizing the total length of busy periods for evacuation mode and for continuation mode operation, respectively, and 2) no optimal scheduling policy can possibly exist in terms of minimizing the average delay under either evacuation mode or continuation mode operation.

关键词： Timing Intelligent networks Length measurement Delay effects computer architecture Media Access Protocol Scattering Broadcasting Switches Laboratories

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Multiplexing statistical real-time channels in a multi-access network

Multiplexing statistical real-time channels in a multi-acces...

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International Conference on Distributed computing Systems

作者： Chih-Che Chou E.G. Shin Bell Laboratories Lucent Technologies Inc. Westminster CO USA Real-Time Computing Laboratory Department of Electrical Thg. and Computer Science University of Michigan Ann Arbor MI USA

Given the client's traffic-generation characteristics and performance requirements, we propose a real-time communication scheme that provides delivery delay guarantees in a multiaccess local-area network (LAN). This scheme (i) reduces the link capacity that needs to be reserved to an average level as compared to the worst-case level required for deterministic performance guarantees, and (ii) preserves the ability of independent addition and deletion of real-time channels.

关键词： Intelligent networks Telecommunication traffic Traffic control Local area networks real time systems Laboratories Circuits Ink Resource management

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A Checkpointing Model for Fault-Tolerant real-time Systems

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IFAC Proceedings Volumes 1996年第1期29卷 7118-7123页

作者： A.K. Ganesh T.J. Marlowe J. Salinas A.D. Stoyenko Real-Time Computing Lab Department of Computer & Information Science New Jersey Institute of Technology University Heights Newark NJ 07102 USA Dept. of Math and CS Seton Hall University South Orange NJ 07079 USA Naval Undersea Warfare Center Newport RI 02841 USA

A Fault-Tolerant real-time System must provide critical level of service in a timely manner in the presence of one or more hardware or software faults. This paper argues that support from the language, environment, and compiler is required. An integrated approach to providing this support through a novel data classification is proposed. This can in principle provide provide static guarantees of timeliness in a checkpointing real-time system, and for recovery and continued computation for up to one node or link failure.

关键词： Fault-tolerance real-time systems compiler techniques checkpointing

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Identifying the capability of overlapping computation with communication

Identifying the capability of overlapping computation with c...

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International Conference on Parallel Architecture and Compilation Techniques (PACT)

作者： A. Sohn J. Ku Y. Kodama M. Sato H. Sakane H. Yamana S. Sakai Y. Yamaguchi Computer and Information Science Department New Jersey Institute of Technology Newark NJ USA Computer Architecture Section Electro Technical Laboratory Tsukuba Ibaraki Japan Real World Computing Tsukuba Research Center Tsukuba Ibaraki Japan

Overlapping computation with communication is central to obtaining high performance on distributed-memory multiprocessors. This report explicates the overlapping capability of two distributed-memory multiprocessors: the EM-X and IBM SP-2. The well-known bitonic sorting algorithm is selected for experiments. Various message sizes are used to determine when, where, how much and why overlapping takes place. Experimental results indicate that both multiprocessors would yield up to 30% to 40% overlap of communication time when the message size is approximately 1K integers. EM-X is found to be message-size insensitive yielding high overlap for various message sizes, while SP-2 was effective for the window of message size 512 to 2K integers.

关键词： Delay computer architecture Switches Distributed computing High performance computing Sorting Prototypes Laboratories Yarn Windows

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Design and analysis of a WDMA protocol for passive star-coupled lightwave networks

Design and analysis of a WDMA protocol for passive star-coup...

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IEEE Annual Joint Conference: INFOCOM, IEEE computer and Communications Societies

作者： Chao-Ju Hou Bin Wang Ching-Chih Han Computer Engineering Division Department of Elect. and Comput. Eng. University of Wisconsin Madison WI USA Real-Time Computing Laboratory Department of Elect. Eng. and Comput. Science University of Michigan Ann Arbor MI USA

ISBN: (纸本)0818672935

Based on the POPSMAC protocol proposed in Chung-Sheng Li et al. (1993), we propose an improved medium access protocol for wavelength division multiple access (WDMA) photonic networks. Using the same set of photonic devices as in POPSMAC, the proposed protocol alleviates the drawbacks of the POPSMAC protocol, e.g., invalid data transmissions following receiver collisions and possible acknowledgement packet collisions with header/data packets, while retaining many advantages of POPSMAC. As a result, the network performance in terms of the throughput and the packet delay is improved. Analytical models based on the timing diagram analysis, the continuous-time Markov chain, and the randomization technique are developed to assess the performance of the proposed protocol. The performance is evaluated in terms of channel utilization, mean packet delay, and packet delay distribution with variations in the number of nodes, the offered traffic, the size of data packets, and the network propagation delay. Numerical results show that the proposed protocol achieves better channel utilization and incurs lower packet delays than POPSMAC.

关键词： Access protocols Propagation delay Data communication Optical receivers Throughput Analytical models Timing Performance analysis Telecommunication traffic Traffic control

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PROBING AND FAULT INJECTION OF DEPENDABLE DISTRIBUTED PROTOCOLS

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computer JOURNAL 1995年第4期38卷 286-300页

作者： DAWSON, S JAHANIAN, F Real-Time Computing Laboratory Electrical Engineering and Computer Science Department University of Michigan Ann Arbor MI 48109-2122 United States

Ensuring that a distributed system with strict dependability constraints meets its prescribed specification is a growing challenge that confronts software developers and system engineers. This paper presents a technique for probing and fault injection of fault-tolerant distributed protocols. The proposed technique, called script-driven probing and fault injection, can be used for studying the behaviour of distributed systems and for detecting design and implementation errors of fault-tolerant protocols. The focus of this work is on fault injection techniques that can be used to demonstrate three aspects of a target protocol: detection of design or implementation errors;identification of violations of protocol specifications;and insight into design decisions made by the implementers. The emphasis of our approach is on experimental techniques intended to identify specific ''problems'' in a protocol or its implementation rather than the evaluation of system dependability through statistical metrics such as fault coverage. To demonstrate the capabilities of this technique, the paper describes a probing and fault injection toot, called the PFI tool (probe/fault injection tool), and a summary of several extensive experiments that studied the behaviour of two protocols: the Transmission Control Protocol (TCP) and a group membership protocol (GMP).

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computing time-DELAY AND ITS EFFECTS ON real-time CONTROL-SYSTEMS

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IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY 1995年第2期3卷 218-224页

作者： SHIN, KG CUI, XZ Real-Time Computing Laboratory Division of Comuuter Science and Engineering. Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

The reliability of a real-time digital control computer depends not only on the reliability of the hardware and software used, but also on the time delay in computing the control output, because of the negative effects of computing time delay on control system performance. For a given fixed sampling interval, the effects of computing time delay are classified into the delay and loss problems, The delay problem, occurs when the computing time delay is nonzero but smaller than the sampling interval, while the loss problem occurs when the computing time delay is greater than, or equal to, the sampling interval, i,e., loss of the control output, These two problems are analyzed as a means of evaluating real-time control systems, First, a generic analysis of the effects of computing time delay is presented along with necessary conditions for system stability, Then, we present both qualitative and quantitative analyses of the computing time delay effects on a robot control system, deriving upper bounds of the computing time delay with respect to system stability and system performance.

关键词： Delay effects real time systems Control systems Sampling methods System performance Stability analysis Digital control Hardware Software performance Performance analysis

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