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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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Evaluation of the Applicability and Profitability of Speculative Execution in real-time Programs

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IFAC Proceedings Volumes 1996年第1期29卷 7147-7152页

作者： Grace Tsai Mohamed F. Younis Behrooz Ghahyazi Thomas J. Marlowe Alexander D. Stoyenko Fairteigh Dickinson University Department of Computer Science Teaneck NJ 07666 USA. New Jersey Institute of Technology Department of Computer and Information Science Real-Time Computing Laboratory Newark NJ 07102 USA Seton Hall University Department of Mathematics and Computer Science South Orange NJ 07079 USA

Speculative execution can enhance the average execution time by executing parts of the code which may or may not be needed. In some cases, rollback is necessary if the computation turns out to be invalid. However, speculative execution should be applied carefully to real-time systems so that the worst-case execution path will not be extended. We have developed a set of compiler transformations to detect safe opportunities for speculative execution in real-time programs and transform the code without jeopardizing the timeliness of the system. To capture various properties of real-time programs that affect applicability and profitability of speculative execution, we have conducted an experiment using randomly generated real-time programs. In this paper, we present simulation results indicating effects of speculative execution on average execution time and program timeliness. In addition, we examine impacts of various program properties, such as locality of variable references, and frequency of conditionals and while loops.

关键词： Compiler transformation real-time Systems Speculative Execution Shadow Execution

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Formal Verification of Transformation Rules for Speculative Execution in real-time Systems

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IFAC Proceedings Volumes 1996年第6期29卷 9-17页

作者： Mohamed Younis Grace Tsai Thomas Marlowe Alexander Stoyenko New Jersey Institute of Technology Department of Computer and Information Science Real-Time Computing Laboratory Newark NJ 07102 USA Fairleigh Dickinson University Department of Computer Science Teaneck NJ 07666 USA. Seton Hall University Department of Mathematics and Computer Science South Orange NJ 07079 USA

There have been a number of successes in the past few years in use of formal methods for verification of real-time systems, and also in source-to-source transformation of these systems for improved analysis, performance, and schedulability. What has been lacking are formal proofs that these transformations preserve, or establish program properties. We have previously developed a set of compiler transformation rules for safe and profitable speculative execution in real-time systems. In this paper, we present formal proofs that our transformations preserve both the semantic and the timeliness properties of programs. Our approach uses temporal logic, enhanced with a denotational-semantics-like representation of program stores.

关键词： Compiler transformation Formal Verification real-time Speculative Execution Temporal Logic

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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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Operator resources for large complex systems

Operator resources for large complex systems

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IEEE International Conference on engineering of Complex computer Systems

作者： M. Harelick A. Stoyenko C. Amaro R. Scherl T.J. Marlowe Real-Time Computing Laboratory Department of Computer and Information Science New Jersey Institute of Technology Newark NJ USA Seton Hall University South Orange NJ USA

Resource allocation in complex systems is studied to determine the best use of software and hardware in order to insure that a system runs smoothly and predictably. Most modern work on this subject does not recognize the effect of humans using and operating these complex systems. We demonstrate how we plan to extend the resource allocation module of the navy sponsored Destination project to take into account the influence of humans.

关键词： Humans Resource management Hardware Timing Laboratories Information science Modems Communication system software Cost function Banking

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On task schedulability in real-time control systems

On task schedulability in real-time control systems

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real-time Systems Symposium (RTSS)

作者： D. Seto J.P. Lehoczky L. Sha K.G. Shin Software Engineering Institute Carnegie Mellon University Pittsburgh PA USA Department of Statistics Carnegie Mellon University Pittsburgh PA USA Real-Time Computing Laboratory Department of Electrical Engineering and Computer Sci University of Michigan Ann Arbor MI USA

Most real-time computer-controlled systems are built in two separate steps, each in isolation: controller design and its digital implementation. Computational tasks that realize the control algorithms are usually scheduled by treating their execution times and periods as unchangeable parameters. Task scheduling therefore depends only on the limited computing resources available. On the other hand, controller design is primarily based on the continuous-time dynamics of the physical system being controlled. The set of tasks resulting from this controller design may not be schedulable with the limited computing resources available. Even if the given set of tasks is schedulable, the overall control performance may not be optimal in the sense that they do not make a full use of the computing resource. We propose an integrated approach to controller design and task scheduling. Specifically, task frequencies (or periods) are allowed to vary within a certain range as long as such a change does not affect critical control functions such as maintenance of system stability. We present an algorithm that optimizes task frequencies and then schedules the resulting tasks with the limited computing resources available. The proposed approach is also applicable to failure recovery and reconfiguration in real-time control systems.

关键词： real time systems Control systems Processor scheduling Scheduling algorithm Digital control Dynamic scheduling System performance Application software Software engineering Statistics

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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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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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Parallel algorithms for force directed scheduling of flattened and hierarchical signal flow graphs

Parallel algorithms for force directed scheduling of flatten...

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IEEE International Conference on computer Design: VLSI in computers and Processors, (ICCD)

作者： P. Prabhakaran P. Banerjee Center for Reliable and High-Performance Computing Coordinated Science Laboratory University of Illinois Urbana IL USA Center for Parallel and Distributed Computing Department of Electrical and Computer Engineering Northwestern University Evanston IL USA

In this paper we present some novel algorithms for scheduling hierarchical signal flow graphs in the domain of high-level synthesis. There are several key contributions of this paper. First, we develop a novel extension of the force directed scheduling problem which naturally handles loops and conditionals by coming up with a scheme of scheduling hierarchical signal flow graphs. Second, we develop three new parallel algorithms for the scheduling problem. Third, our parallel algorithms are portable across a wide range of parallel platforms. We report results on a set of high-level synthesis benchmarks on 8-processor SGI Challenge and a network of 4 SUN SPARCstation5 work stations. Finally, while some parallel algorithms for VLSI CAD reported by earlier researchers have reported a loss of qualities of results, our parallel algorithms produce exactly the same results as the sequential algorithms on which they are based.

关键词： Parallel algorithms Flow graphs Processor scheduling Concurrent computing Scheduling algorithm Contracts Cost function Broadcasting

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Virtual memory versus file interfaces for large, memory-intensive scientific applications 96

Virtual memory versus file interfaces for large, memory-inte...

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Proceedings of the 1996 ACM/IEEE conference on Supercomputing

作者： Yoonho Park Ridgway Scott Stuart Sechrest High Performance Computing Center University of Houston Houston TX Software Systems Research Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI

ISBN: (纸本)9780897918541

Scientific applications often require some strategy for temporary data storage to do the largest possible simulations. The use of virtual memory for temporary data storage has received criticism because of performance problems. However, modern virtual memory found in recent operating systems such as Cenju-3/DE give application writers control over virtual memory policies. We demonstrate that custom virtual memory policies can dramatically reduce virtual memory overhead and allow applications to run out-of-core efficiently. We also demonstrate that the main advantage of virtual memory, namely programming simplicity, is not lost.

关键词： custom policies

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