6609824
Performance-Aware Load Balancing for Multiclusters
In a multicluster architecture, where jobs can be submitted through each constituent cluster, the job arrival rates in individual clusters may be uneven and the load therefore needs to be balanced among clusters. In this paper we investigate load balancing for two types of jobs, namely non-QoS and QoS-demanding jobs and as a result, two performance-specific load balancing strategies (called ORT and OMR) are developed. The ORT strategy is used to obtain the optimised mean response time for non-QoS jobs and the OMR strategy is used to achieve the optimised mean miss rate for QoS-demanding jobs. The ORT and OMR strategies are mathematically modelled combining queuing network theory to establish sets of optimisation equations. Numerical solutions are developed to solve these optimisation equations, and a so called fair workload level is determined for each cluster. When the current workload in a cluster reaches this pre-calculated fair workload level, the jobs subsequently submitted to the cluster are transferred to other clusters for execution. The effectiveness of both strategies is demonstrated through theoretical analysis and experimental verification. The results show that the proposed load balancing mechanisms bring about considerable performance gains for both job types, while the job transfer frequency among clusters is considerably reduced. This has a number of advantages, in particular in the case where scheduling jobs to remote resources involves the transfer of large executable and data files.
2855119
Optimal Scheduling of Aperiodic Jobs on Cluster
This paper presents an algorithm to schedule aperiodic jobs on a cluster system. A cluster consists of one dispatcher and multiple schedulers. The algorithm is optimal for the response time of each aperiodic job. Aperiodic jobs are partitioned into phases and assigned deadlines by the dispatcher. With the deadline, the aperiodic jobs can be scheduled uniformly under EDF (Earliest Deadline First) together with periodic jobs. With rigorous theoretical analysis and proof, we have that even if the dispatcher has no scheduling information, the algorithm can still dispatch the aperiodic jobs onto the proper scheduler to achieve optimal response time and also guarantee the deadline requirements of periodic jobs.
16360889
Optimising static workload allocation in multiclusters
Summary form only given. Workload allocation and job dispatching are two fundamental components in static job scheduling for distributed systems. We address the static workload allocation techniques for two types of job stream in multicluster systems, namely, nonreal-time job streams and soft-real-time job streams, which request different qualities of service. Two workload allocation strategies (called ORT and OMR) are developed by establishing and numerically solving two optimisation equation sets. The ORT strategy achieves the optimised mean response time for the nonreal-time job stream; while the OMR strategy can gain the optimised mean miss rate for the soft-real-time job stream over multiple clusters (these strategies can also be applied in a single cluster system). The effectiveness of both strategies is demonstrated through theoretical analysis. The proposed workload allocation schemes are combined with two job dispatching strategies (weighted random and weighted round-robin) to generate new static job scheduling algorithms for multicluster environments. These algorithms are evaluated through extensive experimental studies and the results show that compared with static approaches without the optimisation techniques, the proposed workload allocation schemes can significantly improve the performance of static job scheduling in multiclusters, in terms of both the mean response time (for the nonreal-time jobs) and the mean miss rate (for soft-real-time jobs).
928092
The impact of predictive inaccuracies on execution scheduling
This paper investigates the underlying impact of predictive inaccuracies on execution scheduling, with particular reference to execution time predictions. This study is conducted from two perspectives: from that of job selection and from that of resource allocation, both of which are fundamental components in execution scheduling. A new performance metric, termed the degree of misperception, is introduced to express the probability that the predicted execution times of jobs display different ordering characteristics from their real execution times due to inaccurate prediction. Specific formulae are developed to calculate the degree of misperception in both job selection and resource allocation scenarios. The parameters which influence the degree of misperception are also extensively investigated. The results presented in this paper are of significant benefit to scheduling approaches that take into account predictive data; the results are also of importance to the application of these scheduling techniques to real-world high-performance systems.
1023314
An Investigation into the Application of Different Performance Prediction Methods to Distributed Enterprise Applications
Response time predictions for workload on new server architectures can enhance Service Level Agreement–based resource management. This paper evaluates two performance prediction methods using a distributed enterprise application benchmark. The historical method makes predictions by extrapolating from previously gathered performance data, while the layered queuing method makes predictions by solving layered queuing networks. The methods are evaluated in terms of: the systems that can be modelled; the metrics that can be predicted; the ease with which the models can be created and the level of expertise required; the overheads of recalibrating a model; and the delay when evaluating a prediction. The paper also investigates how a prediction-enhanced resource management algorithm can be tuned so as to compensate for predictive inaccuracy and balance the costs of SLA violations and server usage.
14206406
Performance-Aware Workflow Management for Grid Computing
Grid middleware development has advanced rapidly over the past few years to support component-based programming models and service-oriented architectures. This is most evident with the forthcoming release of the Globus toolkit (GT4), which represents a convergence of concepts (and standards) from both the grid and web-services communities. Grid applications are increasingly modular, composed of workflow descriptions that feature both resource and application dynamism. Understanding the performance implications of scheduling grid workflows is critical in providing effective resource management and reliable service quality to users. This paper describes a series of extensions to an existing performance-aware grid management system (TITAN). These extensions provide additional support for workflow prediction and scheduling using a multi-domain performance management infrastructure.
15348655
Exploring benefits of non-linear time compression
In comparison to text, audio-video content is much more challenging to browse. Time-compression has been suggested as a key technology that can support browsing-time compression speeds up the playback of audio-video content without causing the pitch to change. Simple forms of time-compression are starting to appear in commercial streaming-media products from Microsoft and Real Networks.In this paper we explore the potential benefits of more recent and advanced types of time compression, called non-linear time compression. The most advanced of these algorithms exploit fine-grain structure of human speech (e.g., phonemes) to differentially speedup segments of speech, so that the overall speedup can be higher. In this paper we explore what are the actual gains achieved by end-users from these advanced algorithms. Our results indicate that the gains are actually quite small in common cases and come with significant system complexity and some audio/video synchronization issues.
9509924
Microarchitecture-level leakage reduction with data retention
In this paper, we study microarchitecture-level leakage energy reduction by power gating. We consider the virtual power/ground rails clamp (VRC) and multithreshold CMOS (MTCMOS) techniques and apply VRC to memory-based units for data retention and MTCMOS to the other units. We propose a systematic methodology for leakage reduction at the microarchitecture level, in which profiling of idle period distribution and ideal power gating analysis are used to select a target component for realistic power gating. We show that the ideal leakage energy reduction can be up to 30% of the total energy for the modern high-performance very long instruction word processors we study and that the secondary level (L2) cache contributes most to the reduction. We further improve the existing adaptive cache decay method for leakage reduction by using VRC for data retention and name it VRC decay . Applied to L2 cache, the VRC decay, on average, increases performance by 5.6% and reduces system energy by 24.1%, compared to the adaptive cache decay without data retention.
6921769
Time-compression: systems concerns, usage, and benefits
With the proliferation of online multimedia content and thepopularity of multimedia streaming systems, it is increasinglyuseful to be able to skim and browse multimedia quickly. A keytechnique that enables quick browsing of multimedia istime-compression. Prior research has described how speech can betime-compressed (shortened in duration) while preserving the pitchof the audio. However, client-server systems providing thisfunctionality have not been available.
In this paper, we first describe the key tradeoffs faced bydesigners of streaming multimedia systems deployingtime-compression. The implementation tradeoffs primarily impact thegranularity of time-compression supported (discrete vs. continuous)and the latency (wait-time) experienced by users after adjustingdegree of time-compression. We report results of user studiesshowing impact of these factors on the average- compression-rateachieved. We also present data on the usage patterns and benefitsof time compression. Overall, we show significant time-savings forusers and that considerable flexibility is available to thedesigners of client-server streaming systems with timecompression.
1018288
Coupled Power and Thermal Simulation with Active Cooling
Power is rapidly becoming the primary design constraint for systems ranging from server computers to handhelds. In this paper we study microarchitecture-level coupled power and thermal simulation considering dynamic and leakage power models with temperature and voltage scaling. We develop an accurate temperature-dependent leakage power model and efficient temperature calculation, and show that leakage energy can be different by up to 10X for temperatures between 35°C and 110°C. Given the growing significance of leakage power and its sensitive dependence on temperature, no power simulation without considering dynamic temperature calculation is accurate. Furthermore, we discuss the thermal runaway induced by the interdependence between leakage power and temperature, and show that in the near future thermal runaway could be a severe problem. We also study the microarchitecture level coupled power and thermal management by novel active cooling techniques that reduce packaging thermal resistance. We show that the direct water-spray cooling technique reduces thermal resistance from 0.8°C/W for conventional packaging to 0.05°C/W, and increases system maximum clock by up to 2.44X under the same thermal constraints.
10647458
Auto-summarization of audio-video presentations
As streaming audio-video technology becomes widespread, there is a dramatic increase in the amount of multimedia content available on the net. Users face a new challenge: How to examine large amounts of multimedia content quickly. One technique that can enable quick overview of multimedia is video summaries; that is, a shorter version assembled by picking important segments from the original.
We evaluate three techniques for automatic creation of summaries for online audio-video presentations. These techniques exploit information in the audio signal (e.g., pitch and pause information), knowledge of slide transition points in the presentation, and information about access patterns of previous users. We report a user study that compares automatically generated summaries that are 20%-25% the length of full presentations to author generated summaries. Users learn from the computer-generated summaries, although less than from authors' summaries. They initially find computer-generated summaries less coherent, but quickly grow accustomed to them.