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3rd IEEE real-time Technology and Applications Symposium

作者： Zuberi, KM Shin, KG Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI 48109-2122 United States

ISBN: (纸本)0818680164

In object-oriented programming, updates to the state variables of objects (by the methods of the object) have to be protected through semaphores to ensure mutual exclusion. Semaphore operations are invoked each time an, object is accessed, and this represents significant run-time overhead. This a's of special concern in cost-conscious, small-size embedded systems such as those used in automotive applications - where costs must be kept to an absolute minimum. Object-oriented programming can be feasible an such applications only if the OS provides efficient, lour-overhead semaphores. We present a new semaphore implementation scheme which saves one context switch per semaphore lod operation in most circumstances and gives performance improvements of 18-25% over traditional semaphore implementation schemes.

关键词： Object oriented programming

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QoS negotiation in real-time systems and its application to automated flight control

QoS negotiation in real-time systems and its application to ...

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3rd IEEE real-time Technology and Applications Symposium

作者： Abdelzaher, TF Atkins, EM Shin, KG Real- Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI 48109-2122 United States

ISBN: (纸本)0818680164

We propose a model for quality-of-service (QoS) negotiation in building real-time services to meet both predictability and graceful degradation requirements. QoS negotiation is shown to (i) outperform conventional ''binary'' admission control schemes (either guaranteeing the required QoS or rejecting the service request), and (ii) achieve higher application-perceived system utility. We incorporated the proposed QoS-negotiation model into an example realtime middleware service, called RTPOOL, which manages a distributed pool of shared computing resources (processors) to guarantee timeliness QoS for real-time applications. The efficacy and power of QoS negotiation are demonstrated for an automated flight control system implemented on a network of PCs running RTPOOL. This system is used to fly an F-16 fighter aircraft modeled using the Aerial Combat (ACM) F-16 Flight Simulator. Experimental results indicate that QoS negotiation, while maintaining real-time guarantees, enables graceful QoS degradation under conditions in which traditional schedulability analysis and admission control schemes fail.

关键词： real time systems

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Comment on a pre-run-time scheduling algorithm for hard real-time systems

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IEEE Transactions on software engineering 1997年第9期23卷 599-600页

作者： Abdelzaher, Tarek F. Shin, Kang G. Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI 48109 United States

In Shepard and Gagne [1], a branch-and-bound implicit enumeration algorithm is described whose purpose is to generate a feasible schedule, if any, for each processor on a multiprocessing node running hard real-time processes. The optimization criterion is to minimize process lateness defined as the difference between the process completion time and deadline. We show in this correspondence that this algorithm does not always succeed in finding a feasible solution, and describe the reason why the algorithm might fail. © 1997 IEEE.

关键词： Branch and bound scheduling algorithm Hard real-time systems Multiprocessors Pre-run-time scheduling Precedence constraints

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Experimental evaluation of failure-detection schemes in real-time communication networks 27

Experimental evaluation of failure-detection schemes in real...

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27th Annual International Symposium on Fault-Tolerant computing, FTCS 1997

作者： Han, Seungjae Shin, Kang G. Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann ArborMI48109-2122 United States

ISBN: (纸本)0818678313

An effective failure-detection scheme is essential for reliable communication services. Most computer network rely on behavior-based detection schemes: each node uses heartbeats to detect the failure of its neighbor nodes, and the transport protocol (like TCP) achieves reliable communication by acknowledgment/retransmission. In this paper, we experimentally evaluate the effectiveness of such behavior-based detection schemes in real-time communication. Specifically, we measure and analyze the coverage and latency of two failure-detection schemes-neighbor detection and end-to-end detection-through fault-injection experiments. The experimental results have shown that a significant portion of failures can be detected very quickly by the neighbor detection scheme, while the end-to-end detection scheme uncovers the remaining failures with larger detection latencies. © 1997 IEEE.

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Scalable hardware priority queue architectures for high-speed packet switches

Scalable hardware priority queue architectures for high-spee...

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3rd IEEE real-time Technology and Applications Symposium

作者： Moon, SW Shin, KG Rexford, J Real-Time Computing Laboratory Dept. of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI 48109 United States Network Mathematics Research Networking and Distributed Systems ATandT Labs Research Murray Hill NJ 07974 United States

ISBN: (纸本)0818680164

In packet-switched networks, queueing of packets at the switches can result when multiple connections share the same physical link. To accommodate a large number of connections, a switch can employ link-scheduling algorithms to prioritize the transmission of the queued packets. Due to the high-speed links and small packet sizes, a hardware solution is needed for the priority queue in order to make the link schedulers effective. But for good performance, the switch should also support a large number of priority levels (P) and be able to buffer a large number of packets (N). So a hardware priority queue design must be both fast and scalable (with respect to N and P) in order to be implemented effectively. In this paper, we first compare four existing hardware priority queue architectures, and identify scalability limitations on implementing these existing architectures for large N and P. Based on our findings, we propose two new priority queue architectures, and evaluate them using simulation results from Verilog HDL and Epoch implementations.

关键词： Computer architecture

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Fast restoration of real-time communication service from component failures in multi-hop networks 97

Fast restoration of real-time communication service from com...

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Proceedings of the ACM SIGCOMM '97 conference on Applications, technologies, architectures, and protocols for computer communication

作者： Seungjae Han Kang G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science The University of Michigan Ann Arbor Michigan

ISBN: (纸本)9780897919050

For many applications it is important to provide communication services with guaranteed timeliness and fault-tolerance at an acceptable level of overhead. In this paper, we present a scheme for restoring real-time channels, each with guaranteed timeliness, from component failures in multi-hop networks. To ensure fast/guaranteed recovery, backup channels are set up a priori in addition to each primary channel. That is, a dependable real-time connection consists of a primary channel and one or more backup channels. If a primary channel fails, one of its backup channels is activated to become a new primary channel. We describe a protocol which provides an integrated solution to the failure-recovery problem (i.e., channel switching, resource re-allocation, ...). We also present a resource sharing method that significantly reduces the overhead of backup channels. The simulation results show that good coverage (in recovering from failures) can be achieved with about 30% degradation in network utilization under a reasonable failure condition. Moreover, the fault-tolerance level of each dependable connection can be controlled, independently of other connections, to reflect its criticality.

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Experimental evaluation of failure-detection schemes in real-time communication networks

Experimental evaluation of failure-detection schemes in real...

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International Symposium on Fault-Tolerant computing (FTCS)

作者： Seungjae Han K.G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

关键词： Intelligent networks Communication networks Computer network reliability Delay Fault detection Telecommunication network reliability Application software Hardware Control systems Computer networks

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An efficient semaphore implementation scheme for small-memory embedded systems

An efficient semaphore implementation scheme for small-memor...

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real-time Technology and Applications Symposium

作者： K.M. Zuberi K.G. Shin Real Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

In object-oriented programming, updates to the state variables of objects (by the methods of the object) have to be protected through semaphores to ensure mutual exclusion. Semaphore operations are invoked each time an object is accessed, and this represents significant run-time overhead. This is of special concern in cost-conscious, small-size embedded systems-such as those used in automotive applications-where costs must be kept to an absolute minimum. Object-oriented programming can be feasible in such applications only if the OS provides efficient, low-overhead semaphores. The authors present a new semaphore implementation scheme which saves one context switch per semaphore lock operation in most circumstances and gives performance improvements of 18-25% over traditional semaphore implementation schemes.

关键词： Embedded system Costs real time systems Object oriented programming Automotive applications Switches Microcontrollers Yarn Embedded computing Laboratories

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Efficient spare-resource allocation for fast restoration of real-time channels from network component failures

Efficient spare-resource allocation for fast restoration of ...

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real-time Systems Symposium (RTSS)

作者： S. Han K.G. Shin Real Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

Since real-time applications usually require not only timeliness but also fault-tolerance, it is essential to incorporate fault-tolerance into real-time communication services that are indispensable to distributed real-time applications. The techniques for failure recovery in datagram communication are not adequate for real-time communication, because they cannot provide recovery-delay guarantees. To ensure fast recovery of a real-time channel from network component failures, we need to reserve network resources (spare resources) along a backup route before failures actually occur. The focus of this paper is on minimizing the amount of spare resources while meeting the fault-tolerance requirement. Specifically, we present resource sharing mechanisms and backup-route selection algorithms, and evaluate their efficiency with extensive simulations.

关键词： Fault tolerance Spread spectrum communication Throughput Computer networks Laboratories Radio access networks Whales IP networks Delay Bandwidth

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Schedule revision in a distributed job shop with the makespan objective

Schedule revision in a distributed job shop with the makespa...

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IEEE International Conference on Robotics and Automation (ICRA)

作者： T. Tsukada K.G. Shin Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

This paper examines the problem of schedule revision in a distributed job shop where the object is to minimize the global makespan. Schedules of work cells may interact through precedence constraints, and a work cell's response to a local schedule disruption may affect schedules of other cells. Complete knowledge about how local schedule changes affect the global schedule may require global knowledge about the schedule. Here, we show that knowledge of only local constraints may be almost as useful as global knowledge for the revision of one cell's schedule. We present simulation results from a general distributed job shop model.

关键词： Job shop scheduling Processor scheduling Manufacturing systems Electrical capacitance tomography Distributed computing Laboratories Computational modeling Computer integrated manufacturing Problem-solving Flexible manufacturing systems

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