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26
Disk Scheduling in a Multimedia I/O system
- in Proceedings of ACM Multimedia'93
, 1993
"... This article provides a retrospective of our original paper by the same title in the Proceedings of the First ACM Conference on Multimedia, published in 1993. This article examines the problem of disk scheduling in a multimedia I/O system. In a multimedia server, the disk requests may have constant ..."
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Cited by 139 (0 self)
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This article provides a retrospective of our original paper by the same title in the Proceedings of the First ACM Conference on Multimedia, published in 1993. This article examines the problem of disk scheduling in a multimedia I/O system. In a multimedia server, the disk requests may have constant data rate requirements and need guaranteed service. We propose a new scheduling algorithm, SCAN-EDF, that combines the features of SCAN type of seek optimizing algorithm with an Earliest Deadline First (EDF) type of real-time scheduling algorithm. We compare SCAN-EDF with other scheduling strategies and show that SCAN-EDF combines the best features of both SCAN and EDF. We also investigate the impact of buffer space on the maximum number of video streams that can be supported. We show that by making the deadlines larger than the request periods, a larger number of streams can be supported. We also describe how we extended the SCAN-EDF algorithm in the PRISM multimedia architecture. PRISM is an integrated multimedia server, designed to satisfy the QOS requirements of multiple classes of requests. Our experience in implementing the extended SCAN-EDF algorithm in a generic operating system is discussed and performance metrics and results are presented to illustrate how the SCAN-EDF extensions and implementation strategies have succeeded in meeting the QOS requirements of different classes of requests.
I/O Issues in a Multimedia System
- IEEE Computer Magazine
, 1994
"... In this paper, we look at the various I/O issues in a multimedia system. In a multimedia server, the disk requests may have constant data rate requirements and need guaranteed service. We study the impact of the real-time nature of the I/O requests on the various components of the I/O system. We stu ..."
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Cited by 136 (4 self)
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In this paper, we look at the various I/O issues in a multimedia system. In a multimedia server, the disk requests may have constant data rate requirements and need guaranteed service. We study the impact of the real-time nature of the I/O requests on the various components of the I/O system. We study the impact of disk scheduling algorithms on the performance of a multimedia system. We investigate the impact of buer space on the maximumnumber of video streams that can be supported. We show that by making the deadlines larger than the request periods, a larger number of streams can be supported. We also show how deadline extension helps in utilizing multiple disks on a single SCSI bus. 2
On real-time capacity limits of multihop wireless sensor networks
- In IEEE RTSS
, 2004
"... Multihop wireless sensor networks have recently emerged as an important embedded computing platform. This paper defines a quantitative notion of real-time capacity of a wireless network. Real-time capacity describes how much real-time data the network can transfer by their deadlines. A capacity boun ..."
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Cited by 56 (5 self)
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Multihop wireless sensor networks have recently emerged as an important embedded computing platform. This paper defines a quantitative notion of real-time capacity of a wireless network. Real-time capacity describes how much real-time data the network can transfer by their deadlines. A capacity bound is derived that can be used as a sufficient schedulability condition for a class of fixedpriority packet scheduling algorithms. Using this bound, a designer can perform capacity planning prior to network deployment to ensure satisfaction of applications ’ real-time requirements. 1
A Utilization Bound for Aperiodic Tasks and Priority Driven Scheduling”,
- IEEE Trans. On Computers,
, 2004
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A feasible region for meeting aperiodic end-to-end deadlines in resource pipelines
- in ICDCS
, 2004
"... This paper generalizes the notion of utilization bounds for schedulability of aperiodic tasks to the case of distributed resource systems. In the basic model, aperiodically arriving tasks are processed by multiple stages of a resource pipeline within end-to-end deadlines. The authors consider a mult ..."
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Cited by 32 (7 self)
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This paper generalizes the notion of utilization bounds for schedulability of aperiodic tasks to the case of distributed resource systems. In the basic model, aperiodically arriving tasks are processed by multiple stages of a resource pipeline within end-to-end deadlines. The authors consider a multi-dimensional space in which each dimension represents the instantaneous utilization of a single stage. A feasible region is derived in this space such that all tasks meet their deadlines as long as pipeline resource consumption remains within the feasible region. The feasible region is a multi-dimensional extension of the single-resource utilization bound giving rise to a bounding surface in the utilization space rather than a scalar bound. Extensions of the analysis are provided to non-independent tasks and arbitrary task graphs. We evaluate the performance of admission control using simulation, as well as demonstrate the applicability of these results to task schedulability analysis in the total ship computing environment envisioned by the US navy. Keywords: Real-time scheduling, schedulability analysis, utilization bounds, aperiodic tasks, total ship computing environment. 1
A Synthetic Utilization Bound for Aperiodic Tasks with Resource Requirements
, 2003
"... Utilization bounds for schedulability of aperiodic tasks are new in real-time scheduling literature. All aperiodic bounds known to date apply only to independent tasks. They either assume a liquid task model (one with infinitely many infinitesimal tasks) or are limited to deadline-monotonic and earl ..."
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Cited by 24 (6 self)
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Utilization bounds for schedulability of aperiodic tasks are new in real-time scheduling literature. All aperiodic bounds known to date apply only to independent tasks. They either assume a liquid task model (one with infinitely many infinitesimal tasks) or are limited to deadline-monotonic and earliest-deadline first scheduling. In this paper, the authors make two important contributions. First, they derive the first aperiodic utilization bound that considers a task model with resource requirements. Second, the new bound is a function of a parameter called preemptable deadline ratio that depends on the scheduling policy. We show that many scheduling policies can be classified by this parameter allowing per-policy bounds to be derived. Simulation results demonstrating the applicability of aperiodic utilization bounds are presented.
Efficient scheduling for periodic aggregation queries in multihop sensor networks
, 2012
"... In this paper, we study periodic query scheduling for data aggregation with minimum delay under various wireless interference models. Given a set of periodic aggregation queries, each query has its own period and the subset of source nodes containing the data. We first propose a family of efficient ..."
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Cited by 18 (6 self)
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In this paper, we study periodic query scheduling for data aggregation with minimum delay under various wireless interference models. Given a set of periodic aggregation queries, each query has its own period and the subset of source nodes containing the data. We first propose a family of efficient and effective real-time scheduling protocols that can answer every job of each query task within a relative delay under resource constraints by addressing the following tightly coupled tasks: routing, transmission plan constructions, node activity scheduling, and packet scheduling. Based on our protocol design, we further propose schedulability test schemes to efficiently and effectively test whether, for a set of queries, each query job can be finished within a finite delay. Our theoretical analysis shows that our methods achieve at least a constant fraction of the maximum possible total utilization for query tasks, where the constant depends on wireless interference models. We also conduct extensive simulations to validate the proposed protocol and evaluate its practical performance. The simulations corroborate our theoretical analysis.
Hard Real-Time Communication in Multiple-Access Networks
- Real-time Systems
, 1995
"... . With the increasing use of distributed hard real-time systems, the ability of computer networks to handle hard real-time message traffic is becoming more important. For traditional networks, maximizing the throughput or minimizing the average message delay is the most important performance criteri ..."
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Cited by 12 (2 self)
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. With the increasing use of distributed hard real-time systems, the ability of computer networks to handle hard real-time message traffic is becoming more important. For traditional networks, maximizing the throughput or minimizing the average message delay is the most important performance criteria. In the hard real-time domain, however, concern focuses on satisfying the time constraints of individual messages. This paper examines recent developments in hard real-time communication in local area multiple-access networks. Two general strategies are used in hard real-time communication: the guarantee strategy and the best-effort strategy. In the former, messages are guaranteed to meet their deadlines during normal operation of the network. In the best-effort strategy, the network will attempt to send messages before their deadlines, but no guarantees are given. Real-time message traffic can be distinguished according to whether it is best suited for the guarantee strategy or the best-e...
The Aperiodic Multiprocessor Utilization Bound for Liquid Tasks
- In Real-time and Embedded Technology and Applications Symposium
, 2002
"... Real-time scheduling theory has developed powerful tools for translating conditions on aggregate system utilization into per-task schedulability guarantees. The main breakthrough has been Liu and Layland's utilization bound for schedulability of periodic tasks. In 2001 this bound was generalize ..."
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Cited by 11 (4 self)
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Real-time scheduling theory has developed powerful tools for translating conditions on aggregate system utilization into per-task schedulability guarantees. The main breakthrough has been Liu and Layland's utilization bound for schedulability of periodic tasks. In 2001 this bound was generalized by Abdelzaher and Lu to the aperiodic task case. In this paper, we further generalize the aperiodic bound to the case of multiprocessors, and present key new insights into schedulability analysis of aperiodic tasks.
Run-Time Monitoring of Real-Time Systems
- in Advances in Real-time Systems, Prentice-Hall
, 1995
"... Introduction In designing real-time systems, we often make assumptions about the behavior of the system and its environment. These assumptions take many forms, such as upper bounds on interprocess communication delay, deadlines on the execution of tasks, or minimum separations between occurrences o ..."
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Cited by 9 (0 self)
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Introduction In designing real-time systems, we often make assumptions about the behavior of the system and its environment. These assumptions take many forms, such as upper bounds on interprocess communication delay, deadlines on the execution of tasks, or minimum separations between occurrences of two events. They are often made to deal with the unpredictability of the external environment or to simplify a problem that is otherwise intractable or very hard to solve. Such assumptions may be expressed as part of the formal specification of the system or as scheduling requirements on real-time computations. Despite the contributions of formal verification methods and real-time scheduling results in recent years, the need to perform run-time monitoring of these systems is not diminished, for several reasons: the execution environment of most systems is imperfect and the interaction with the external world introduces additional unpredictability; design assumptions can be violated
