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Proceedings. Real-Time Systems Symposium

6-8 Dec 1988

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Displaying Results 1 - 25 of 30
  • Process dependent static cache partitioning for real-time systems

    Publication Year: 1988, Page(s):181 - 190
    Cited by:  Papers (16)  |  Patents (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (912 KB)

    The author investigates the use of a priori knowledge of program behavior to partition an instruction cache of size C into a static partition of size S and an LRU partition of size C -S. The value of S is task-dependent and is nonzero for most programs running on the system. Example programs are presented, and their behavior in various size caches is di... View full abstract»

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  • Implementation and evaluation of a time-driven scheduling processor

    Publication Year: 1988, Page(s):172 - 180
    Cited by:  Papers (7)  |  Patents (5)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (724 KB)

    C.D. Locke developed a heuristic, best-effort (BE) time-driven scheduling policy (Ph.D. thesis, Dept. of Comput. Sci., Carnegie-Mellon Univ., (1986)) and demonstrated its superiority to simpler policies using extensive simulations. The author describes an implementation of Locke's BE policy that uses a dedicated scheduling processor to reduce the scheduling overhead significantly. The scheduler wa... View full abstract»

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  • Allocation of real-time computations under fault tolerance constraints

    Publication Year: 1988, Page(s):161 - 170
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (860 KB)

    An allocation scheme is proposed that accomplishes the hard real-time goal of guaranteeing a deadline satisfaction in case the job is accepted. In addition, the scheme supports fault-tolerance objectives in both damage containment and resiliency requirements. It does this in cooperation with a schedulability verification mechanism and with an object architecture in which for each object there exis... View full abstract»

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  • A comparison of four adaptation algorithms for increasing the reliability of real-time software

    Publication Year: 1988, Page(s):232 - 241
    Cited by:  Papers (7)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (704 KB)

    In a large, parallel, real-time computer system, it is frequently most cost-effective to use different software reliability techniques (e.g., retry, replication, and resource-allocation algorithms) at different levels of granularity or within different subsystems, dependent on the reliability requirements and fault models associated with each subsystem. The authors describe the results of applying... View full abstract»

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  • The integration of deadline and criticalness in hard real-time scheduling

    Publication Year: 1988, Page(s):152 - 160
    Cited by:  Papers (43)  |  Patents (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (700 KB)

    Two task-scheduling algorithms for distributed hard real-time computer systems are presented. Both algorithms are based on a heuristic approach and explicitly account for both the deadlines and criticality of tasks when making scheduling decisions. In analyzing the algorithms, a performance metric called the weighted guarantee ratio is defined. It reflects both the percentage of tasks that make th... View full abstract»

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  • MELODY: a distributed real-time testbed for adaptive systems

    Publication Year: 1988, Page(s):112 - 119
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (648 KB)

    The authors analyze current and future needs in building adaptive real-time systems and formulate a series of design requirements for their hardware/interconnection, operating system, and application levels that could be satisfied together only in an integrated system design. They describe the major features of the corresponding model. On the operating-system level, novel services are rendered by ... View full abstract»

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  • Execution of a high level real-time language

    Publication Year: 1988, Page(s):69 - 76
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (712 KB)

    Prototype system description language is a high-level real-time language with special features for hard real-time system specification and design. It can be used to firm up requirements through execution of its software prototypes. The language design is based on a real-time model merging data and control flow, and its implementation is beyond conventional compiler technology because of the need t... View full abstract»

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  • Evaluation of the probability of dynamic failure and processor utilization for real-time systems

    Publication Year: 1988, Page(s):222 - 231
    Cited by:  Papers (6)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (628 KB)

    It is shown how to determine closed-form expressions for task scheduling delay and active task time distributions for any real-time system application, given a scheduling policy and task execution time distributions. The active task time denotes the total time a task is executing or waiting to be executed, including scheduling delays and resource contention delays. The distributions are used to de... View full abstract»

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  • Real-time synchronization protocols for multiprocessors

    Publication Year: 1988, Page(s):259 - 269
    Cited by:  Papers (143)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (1028 KB)

    The authors investigate the synchronization problem in the context of priority-driven preemptive scheduling on shared-memory multiprocessors. Unfortunately, a direct application of synchronization mechanisms such as the Ada rendezvous, semaphores, or monitors can lead to uncontrolled priority inversion: a high job being blocked by a lower priority job for an indefinite period of time. A task alloc... View full abstract»

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  • Minimizing mean flow time with release time and deadline constraints

    Publication Year: 1988, Page(s):24 - 32
    Cited by:  Papers (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (672 KB)

    The problem of preemptively scheduling a task system consisting of a set of n independent tasks on one processor so as to minimize the mean flow time is considered. The goal is to find a preemptive schedule such that the mean flow time is minimized subject to the constraint that task Ti is executed within the interval between its release time and its deadline. Such a s... View full abstract»

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  • Algorithms for scheduling periodic jobs to minimize average error

    Publication Year: 1988, Page(s):142 - 151
    Cited by:  Papers (18)  |  Patents (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (680 KB)

    Several preemptive, priority-driven algorithms for scheduling periodic jobs on systems that support imprecise computations are described and evaluated. The algorithms are designed to keep the average error in the results produced over consecutive periods small. The approach taken here is to consider each task as consisting of two parts: a mandatory part that must be completed in order for the task... View full abstract»

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  • Semantics of a real-time language

    Publication Year: 1988, Page(s):106 - 110
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (496 KB)

    The authors describe the semantics of the real-time language PSDL, which was designed for prototyping real-time systems. They focus on the aspects of the language relating to hard real-time constraints, scheduling, and functional behavior. They present the aspects of PSDL that simplify the description of real-time constraints and clarify the relationships between periodic and data-driven operators... View full abstract»

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  • Missile guidance processor software development-a case study

    Publication Year: 1988, Page(s):60 - 68
    Cited by:  Patents (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (520 KB)

    A case study of a near-complete implementation of a real-time software system is presented. The software implements a missile guidance processor control system. The languages of implementation are C and assembler, targeted to an MC68020 central processing unit with an MC68881 floating-point coprocessor and an HD63450 direct memory access controller. Modern software engineering practices were used,... View full abstract»

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  • On the graceful degradation of phase-locked clocks

    Publication Year: 1988, Page(s):202 - 211
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (472 KB)

    The use of phase-locked clocks to limit clock skews to fractions of the clock period while keeping the algorithm overhead very small is investigated. The number of clocks in the system required to ensure that up to m arbitrary failures can be tolerated with all the good clocks still in synchrony has been shown to be N⩾3m+1. It is shown here that, if N⩽3 ... View full abstract»

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  • Exploiting unused periodic time for aperiodic service using the extended priority exchange algorithm

    Publication Year: 1988, Page(s):251 - 258
    Cited by:  Papers (35)  |  Patents (13)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (696 KB)

    Real-time scheduling algorithms that provide responsive aperiodic service in the presence of hard real-time periodic tasks require the creation of a high-priority periodic server task for servicing aperiodic requests. The authors describe the extended priority exchange algorithm, which can provide better aperiodic response than previous aperiodic service algorithms, particularly for cases where th... View full abstract»

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  • State-based specification of complex real-time systems

    Publication Year: 1988, Page(s):2 - 11
    Cited by:  Papers (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (800 KB)

    A state-based specification methodology for real-time systems is presented that reduces the number of states by orders of magnitude compared to standard techniques and provides explicit representation for temporal constraints. Formal definitions and a graphic notation for the associated hierarchical multistate (HMS) machines are presented, and various concepts of hierarchy of HMS machines are expl... View full abstract»

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  • Guaranteeing deadlines in MAFT

    Publication Year: 1988, Page(s):130 - 139
    Cited by:  Papers (4)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (636 KB)

    The author discusses scheduling in the multicomputer architecture for fault-tolerance (MAFT), a distributed system designed to provide extremely reliable computation in real-time control systems. Scheduling in MAFT is based on a fault-tolerant variation of a priority-list schedule. The threading delay associated with agreement on task completions can cause schedules to experience Richards' anomali... View full abstract»

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  • Expressing and maintaining timing constraints in FLEX

    Publication Year: 1988, Page(s):96 - 105
    Cited by:  Papers (25)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (780 KB)

    The timing constraint mechanism in a real-time programming language called FLEX is described. A FLEX program can use the constraint primitives to express timing and resource requirements. If the required time or resources are not available at run-time, a FLEX program can dynamically produce monotonic imprecise results. Both time and system resources are defined as first-class objects in the langua... View full abstract»

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  • A real time parallel processing data acquisition system

    Publication Year: 1988, Page(s):54 - 59
    Cited by:  Papers (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (368 KB)

    The design of a VME-based parallel-processing data-acquisition system for the proposed TRIUMF/UBC positron emission tomographs is described. Event records, consisting of eight bytes of data, must be acquired and digitally processed at rates of 250000 to 500000 events per second, corresponding to a data acquisition rate of up to 4 Mb/s. Real-time processing is necessary to reduce the data storage r... View full abstract»

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  • Support for high-priority traffic in VLSI communication switches

    Publication Year: 1988, Page(s):191 - 200
    Cited by:  Papers (2)  |  Patents (6)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (748 KB)

    The design of small n×n switches that can be used to construct communication networks that provide low-latency communication for high-priority traffic, which is required for both multistage interconnection networks used in multiprocessors and direct networks used in multicomputers. The focus is on the design of the internal buffers, specifically on the design of buffers tha... View full abstract»

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  • On-line scheduling of real-time tasks

    Publication Year: 1988, Page(s):244 - 250
    Cited by:  Papers (24)  |  Patents (11)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (516 KB)

    The problem of online scheduling of a set of n independent, real-time tasks on m⩾1 identical processors is addressed. An online scheduler is said to be optimal if it performs as well as the best offline scheduler. It is shown that no optimal online scheduler can exist if the tasks have more than one distinct deadline. An optimal online scheduler for tasks with one common dead... View full abstract»

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  • The cyclic executive model and Ada

    Publication Year: 1988, Page(s):120 - 129
    Cited by:  Papers (26)  |  Patents (3)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (928 KB)

    Periodic processes are major parts of many real-time embedded computer applications. The programming language Ada permits programming of simple periodic processes, but it has some serious limitations: producing Ada programs with real-time performance comparable to that of programs produced to date using traditional cyclic executives requires techniques that are specific to one machine or compiler.... View full abstract»

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  • What's `real' about real-time systems?

    Publication Year: 1988, Page(s):78 - 85
    Cited by:  Papers (5)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (640 KB)

    A real-time system is a concurrent computing system whose computations and actions must satisfy time constraints. Guaranteeing that such a system will meet its constraints can be viewed either in terms of an extended model of program correctness or as a problem of scheduling, e.g. establishing a feasible schedule. However, a crucial distinction between real-time and other concurrent programs is no... View full abstract»

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  • Estimating task response time with contentions for real-time distributed systems

    Publication Year: 1988, Page(s):272 - 281
    Cited by:  Papers (2)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (720 KB)

    Response time is affected by interprocessor communications, precedence relationships among the modules, module assignments, and processor scheduling policies. Furthermore, due to sharing of resources and data among the processors, contention delays are incurred. A task response time model that considers all these factors is proposed. A Petri net is used to represent resource contention, and the ta... View full abstract»

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  • Optimal resource control in periodic real-time environments

    Publication Year: 1988, Page(s):33 - 41
    Cited by:  Papers (1)
    Request permission for commercial reuse | Click to expandAbstract | PDF file iconPDF (560 KB)

    Three factors determine the optimum configuration of a multiprocessor at any epoch: the workload, the reward structure, and the state of the computer system. An algorithm is presented for the optimal (more realistically, quasi-optimal) configuration of such systems used in real-time applications with periodic reward rates and workloads. The algorithm is based on Markov decision theory. It is sugge... View full abstract»

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