26 research outputs found

    Adaptive Dispatching of Tasks in the Cloud

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    The increasingly wide application of Cloud Computing enables the consolidation of tens of thousands of applications in shared infrastructures. Thus, meeting the quality of service requirements of so many diverse applications in such shared resource environments has become a real challenge, especially since the characteristics and workload of applications differ widely and may change over time. This paper presents an experimental system that can exploit a variety of online quality of service aware adaptive task allocation schemes, and three such schemes are designed and compared. These are a measurement driven algorithm that uses reinforcement learning, secondly a "sensible" allocation algorithm that assigns jobs to sub-systems that are observed to provide a lower response time, and then an algorithm that splits the job arrival stream into sub-streams at rates computed from the hosts' processing capabilities. All of these schemes are compared via measurements among themselves and with a simple round-robin scheduler, on two experimental test-beds with homogeneous and heterogeneous hosts having different processing capacities.Comment: 10 pages, 9 figure

    Fairness in non-convex systems

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    In general, the set of users utilities is boundedbecause of the limitation of resources. There may existmany Pareto optimal points in the set of users utilities.For selecting a Pareto optimum point, a family of fairnesscriteria, that contains the max-min fairness and aparameterized family of fairness (by Mo andWalrand), hasbeen proposed and examined in some concrete networkingcontexts that result in specific convex utility sets. We newlyexamine general compact (closed and bounded) utility setswhich include the specific utility sets as special cases. Wefirst prove that each of the family of fairness criteria givesa unique fair (Pareto optimum) point if the utility set isconvex. We find, however, counter-examples where each ofthe family of fairness criteria gives multiple fair points ifthe utility set is not convex. We propose an extention of thefamily of fairness criteria such that each of them gives onlya unique fair point regardless of whether the utility set isconvex or not, to which we give proofs. By using a specificload balancing model, we illustrate the counter-examplesand how each criterion of our extended fair family givesa unique fair point

    Fault-tolerant de Bruijn and shuffle-exchange networks

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    This paper addresses the problem of creating a fault-tolerant interconnection network for a parallel computer. Three topologies, namely, the base-2 de Bruijn graph, the base-m de Bruijn graph, and the shuffle-exchange, are studied. For each topology an N+k node fault-tolerant graph is defined. These fault-tolerant graphs have the property that given any set of k node faults, the remaining N nodes contain the desired topology as a subgraph. All of the constructions given are the best known in terms of the degree of the fault-tolerant graph. We also investigate the use of buses to reduce the degrees of the fault-tolerant graphs still further

    Distributed management based on mobile agents

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    During the forthcoming years, Internet-based concepts will continue to revolutionize, in an unpredictable way, the mode enterprises provide, maintain and use traditional information technology. Management systems will be a crucial issue in the struggle with this crescent complexity. However, new requirements have to be considered, due to the expectation of enormous quantities of different elements, ranging from an impressive network bandwidth availability to multimedia QoS-constrained services. Many researchers believe that mobile agent paradigm can provide effective solutions on these new scenarios. This paper presents an implementation of management applications supported upon distribution and delegation concepts. For that it uses the current work of IETF’s Disman working group enhanced with mobility provision. The mobility allows the distributed managers to adapt dynamically to a mutable environment optimizing the use of network resources

    Fault-tolerant de Bruijn and shuffle-exchange networks

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    Utilization-based techniques for statically mapping heterogeneous applications onto the HiPer-D hetergeneous computing system

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    Includes bibliographical references (pages 16-18).This research investigates the problem of allocating a set of heterogeneous applications to a set of heterogeneous machines connected together by a high-speed network. The proposed resource allocation heuristics were implemented on the High Performance Distributed Computing Program's (HiPer-D) Naval Surface Warfare Center testbed. The goal of this study is to design static resource allocation heuristics that balance the utilization of the computation and network resources while ensuring very low failure rates. A failure occurs if no allocation is found that allows the system to meet its resource and quality of service constraints. The broader goal is to determine an initial resource allocation that maximizes the time before run-time re-allocation is required for managing an increased workload. This study proposes two heuristics that perform well with respect to the load-balancing and failure rates. These heuristics are, therefore, very desirable for HiPer-D like systems where low failure rates can be a critical requirement

    Effects of symmetry on Braess-like paradoxes in distributed computer systems - A numerical study

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    Abstract Numerical examples of a Braess-like paradox in which adding capacity to a distributed computer system may degrade the performance of all users in the system have already been reported. Unlike the original Braess paradox, this behavior occurs only in the case of finitely many users and not in the case of infinite number of users in the models examined. This study examines a number of numerical examples around the Braess-like paradox such as above. The numerical examples suggest that the Braess-like paradox is stronger, i.e., the performance degradation of all users in the Brass-like paradox is larger when the system has a higher degree of symmetry and, in particular, is strongest in the completely symmetrical system whereby the parameter values describing each user are identical, which is against our previous intuition
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