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Software, IET

Issue 6 • Date December 2009

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Displaying Results 1 - 7 of 7
  • Performance engineering - editorial

    Page(s): 443 - 444
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (128 KB)  

    Imperial College London was host to the 24th Annual UK Performance Engineering Workshop in July 2008. UKPEW is an enjoyable workshop that brings together researchers in the performance engineering community to discuss quantitative aspects of, for instance, Grid computing, web and e-commerce, performance modelling techniques, power management and wireless network performance. In 2008, we had 29 papers presented over the two days of the workshop and this IET Software Special Issue represents significantly extended versions of the best selected papers from that workshop. View full abstract»

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  • Which battery model to use?

    Page(s): 445 - 457
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    The use of mobile devices like cell phones, navigation systems or laptop computers is limited by the lifetime of the included batteries. This lifetime depends naturally on the rate at which energy is consumed; however, it also depends on the usage pattern of the battery. Continuous drawing of a high current results in an excessive drop of residual capacity. However, during intervals with no or very small currents, batteries do recover to a certain extent. The usage pattern of a device can be well modelled with stochastic workload models. However, one still needs a battery model to describe the effects of the power consumption on the state of the battery. Over the years many different types of battery models have been developed for different application areas. In this study we give a detailed analysis of two well-known analytical models, the kinetic battery model (KiBaM) and the so-called diffusion model. We show that the KiBaM is actually an approximation of the more complex diffusion model; this was not known previously. Furthermore, we tested the suitability of these models for performance evaluation purposes, and found that both models are well suited for doing battery lifetime predictions. However, one should not draw conclusions on what is the best usage pattern based on only a few workload traces. View full abstract»

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  • Fine-grain stochastic modelling of dynamic power management policies and analysis of their power - latency tradeoffs

    Page(s): 458 - 469
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (582 KB)  

    Dynamic power management (DPM) is one of the main system-level low-power techniques for portable devices. This study presents a fine-grain Markov modelling approach that enables accurate analysis of system power and latency characteristics with full consideration of mode switching overheads in both processor and power controller. The new approach also makes it possible to incorporate latency analysis in terms of deadline satisfaction. View full abstract»

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  • Performance of locality-aware topologies for peer-to-peer live streaming

    Page(s): 470 - 479
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (874 KB)  

    This study is concerned with the effect of overlay network topology on the performance of live streaming peer-to-peer systems. The study focuses on the evaluation of topologies which are aware of the delays experienced between different peers on the network. Metrics are defined which assess the topologies in terms of delay, bandwidth usage and resilience to peer drop-out. Several topology creation algorithms are tested and the metrics are measured in a simple simulation testbed. This gives an assessment of the type of gains, which might be expected from locality awareness in peer-to-peer networks. View full abstract»

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  • Analytical TCP throughput model for high-speed downlink packet access

    Page(s): 480 - 494
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (467 KB)  

    This study deals with the throughput analysis of data services over high-speed downlink packet access (HSDPA) systems. The achievable throughput is calculated with an approximate analytical method based on the Padhye model that has two input parameters: the packet loss probability and the transmission control protocol (TCP) round trip time. The proposed solution is to calculate these parameters with an equivalent queuing network model of the HSDPA system that takes into account the possible congestion points in the system and the protocol layers that have dominant impact on the delay and packet drop. The modelling considerations and the analysis method are described in detail. Finally, the model is validated with a performance study of the HSDPA system that is executed with detailed NS2-based simulations too. The proposed method is found to be reasonably accurate requiring less computational effort than the simulations. View full abstract»

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  • Transient calculations on process algebra derived Markov chains

    Page(s): 495 - 508
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    The process of obtaining transient measures from a Markov chain as implemented in the software, ipclib is described. The software accepts models written in PEPA, Bio-PEPA or as a Petri net. In the case of the process algebras, a rich query specification language particularly well suited for the derivation of passage-time quantiles is provided. Such measurements are obtained from the derived Markov chain through a process known as uniformisation. The authors detail how the process algebra and query specification language allow one to ensure that the passage-time calculation is valid and then the entire process through to the final calculation of the cumulative distribution and probability density functions of the passage in question. The authors also show a more generic transient measure for which the full probability distributions at specific times are required. View full abstract»

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  • Performance prediction and procurement in practice: assessing the suitability of commodity cluster components for wavefront codes

    Page(s): 509 - 521
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (690 KB)  

    The cost of state-of-the-art supercomputing resources makes each individual purchase a length and expensive process. Often each candidate architecture will need to be benchmarked using a variety of tools to assess likely performance. However, benchmarking alone only provides a limited insight into the suitability of each architecture for key codes and will give potentially misleading results when assessing their scalability. In this study the authors present a case study of the application of recently developed performance models of the Chimaera benchmarking code written by the United Kingdom Atomic Weapons Establishment (AWE), with a view to analysing how the code will perform and scale on a medium sized, commodity-based InfiniBand cluster. The models are validated and demonstrate a greater than 90% accuracy for an existing InfiniBand machine; the models are then used as the basis for predicting code performance on a variety of alternative hardware configurations which include changes in the underlying network, the use of faster processors and the use of a higher core density per processor. The results demonstrate the compute-bound nature of Chimaera and its sensitivity to network latency at increased processor counts. By using these insights the authors are able to discuss potential strategies which may be employed during the procurement of future mid-range clusters for wavefront-rich workloads. View full abstract»

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