14096392
Mapping DAG-based applications to multiclusters with background workload
Before an application modelled as a directed acyclic graph (DAG) is executed on a heterogeneous system, a DAG mapping policy is often enacted. After mapping, the tasks (in the DAG-based application) to be executed at each computational resource are determined. The tasks are then sent to the corresponding resources, where they are orchestrated in the pre-designed pattern to complete the work. Most DAG mapping policies in the literature assume that each computational resource is a processing node of a single processor, i.e. the tasks mapped to a resource are to be run in sequence. Our studies demonstrate that if the resource is actually a cluster with multiple processing nodes, this assumption will cause a mis-perception in the tasks' execution time and execution order. This will disturb the pre-designed cooperation among tasks so that the expected performance cannot be achieved. In this paper, a DAG mapping algorithm is presented for multicluster architectures. Each constituent cluster in the multicluster is shared by background workload (from other users) and has its own independent local scheduler. The multicluster DAG mapping policy is based on theoretical analysis and its performance is evaluated through extensive experimental studies. The results show that compared with conventional DAG mapping policies, the new scheme that we present can significantly improve the scheduling performance of a DAG-based application in terms of the schedule length.
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.
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).
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.
37859827
Optimal dispatching and scheduling for both periodic and aperiodic jobs in cluster
Presents dispatching and scheduling algorithms for both periodic and aperiodic jobs on a cluster of computers. A cluster system consists of one front-end node, called dispatcher and multiple back-end nodes, called schedulers. By rigorous theoretical analysis, these algorithms are optimal in the sense that each aperiodic job can achieve the shortest response time in the cluster while maintaining the schedulability of periodic jobs. The aperiodic jobs, which have no deadline requirement, are partitioned into phases and assigned deadlines by the dispatcher With the deadlines the aperiodic jobs can be scheduled uniformly under EDF together with periodic jobs. Based on extensive simulation studies, we have that the algorithms proposed in the paper can achieve great performance improvement. We also work out the workload zone in which the response time of aperiodic jobs in the cluster with N schedulers is the same as the ideal bound of response time in the corresponding M/M/N model.
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.
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.
2560002
Automating lecture capture and broadcast: technology and videography
Abstract.Our goal is to help automate the capture and broadcast of lectures to online audiences. Such systems have two interrelated design components. The technology component includes hardware and associated software. The aesthetic component comprises the rules and idioms that human videographers follow to make a video visually engaging; these rules guide hardware placement and software algorithms. We report the design of a complete system that captures and broadcasts lectures automatically and report on a user study and a detailed set of video-production rules obtained from professional videographers who critiqued the system, which has been deployed in our organization for 2 years. We describe how the system can be generalized to a variety of lecture room environments differing in room size and number of cameras. We also discuss gaps between what professional videographers do and what is technologically feasible today.
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.
17606652
Solving the Chan-Vese Model by a Multiphase Level Set Algorithm Based on the Topological Derivative
In this work, we specifically solve the Chan-Vese active contour model by multiphase level set methods. We first develop a fast algorithm based on calculating the variational energy of the Chan-Vese model without the length term. We check whether the energy decreases or not when we move a point to another segmented region. Then we draw a connection between this algorithm and the topological derivative, a concept emerged from the shape optimization field. Furthermore, to include the length term of the Chan-Vese model, we apply a preprocessing step on the image by using nonlinear diffusion. We show numerical experiments to demonstrate the efficiency and the robustness of our algorithm.
14821600
Comparing presentation summaries: slides vs. reading vs. listening
As more audio and video technical presentations go online, it becomes imperative to give users effective summarization and skimming tools so that they can find the presentation they want and browse through it quickly. In a previous study, we reported three automated methods for generating audio-video summaries and a user evaluation of those methods. An open question remained about how well various text/image only techniques will compare to the audio-video summarizations. This study attempts to fill that gap.
This paper reports a user study that compares four possible ways of allowing a user to skim a presentation: 1) PowerPoint slides used by the speaker during the presentation, 2) the text transcript created by professional transcribers from the presentation, 3) the transcript with important points highlighted by the speaker, and 4) a audio-video summary created by the speaker. Results show that although some text-only conditions can match the audio-video summary, users have a marginal preference for audio-video (ANOVA f=3.067, p=0.087). Furthermore, different styles of slide-authoring (e.g., detailed vs. big-points only) can have a big impact on their effectiveness as summaries, raising a dilemma for some speakers in authoring for on-demand previewing versus that for live audiences.