Catálogo de publicaciones - libros

Although multi-site MPI execution has been criticized in the past as being ”impractical” due to limitations in network latency and bandwidth, we believe many of the obstacles can be overcome by various means for wider classes of applications than previously believed. One such technique is transparent dynamic migration of MPI, coupled with aggressively performance-oriented overlay networks, assuming availability of gigabits of bandwidth on future WANs. The problem, of course, is to investigate the exact implications to application performances given the arsenal of such techniques, but such work has been quite sparse. Our current work involves using Xen as the underlying virtual machine layer to implement such migration, along with performance-optimizing migration strategies—this particular paper deals with performance evaluations of MPI on Xen VMs including what are the possible performance hindrances, implications of migrations, as well as the effect of variations in latencies and bandwidth parameters as realized by the overlay network using a software network emulator.

The use of virtualization as a means to consolidate multiple applications on the same server platform continues to grow in the datacenter. However, the performance implications in a virtualized environment are not yet thoroughly understood for key commercial server workloads. In this paper, our goal is to provide architectural insights into the performance of server application scaling in a virtualization environment. We do so by studying the scaling behavior of a compute intensive application, namely SPECjbb2005 which is a commercial Java server benchmark. When comparing to native execution, the performance of a single virtual machine running SPECjbb2005 appears to be comparable. However, as the number of virtual machines is increased, the performance degradation was found to be significant. A detailed investigation into overheads of virtual machine scheduling and context switching overhead was conducted. Based on this investigation, we show how the number of instructions executed per operation, the cycles per instruction, and the cache misses and the TLB misses all are affected when scaling virtual machines. We also compare the performance of the simultaneously running virtual machines and discuss fairness and prioritization implications of scheduling decisions.

In this paper, we propose a method to realize compound video (multiple videos on a layout)delivery service for mobile terminals. In the proposed method, we introduce proxies which receive multiple videos from corresponding servers and produce a composite video from the received videos in real-time according to the layouts which users specify. However, if users require sets of videos with slightly different layouts, multiple similar composite videos will be generated and the wireless bandwidth will be suppressed to transfer them. So, the proposed method identifies the common part in layouts of user requirements, and transmits to each user a composite video corresponding to the common part and remaining videos. We have developed a greedy algorithm which calculates the set of videos to be transmitted within the available bandwidth, so that the sum of satisfaction degrees of all users is maximized. Through experiments, we confirmed that our method can achieve much higher user satisfaction degrees compared to the case that each user terminal receives multiple videos separately and plays them back in parallel.

This paper is to present why and how to build a virtual Telematics systems. Diverse traffic data are collected, managed and distributed mainly by government agencies. These agencies, however, have their own unique aims, functions, standards and policies with regard to Intelligent Transportation System (ITS) centers for managing and controlling their own transport systems. It becomes obstacles and barriers to overcome for distributing nationwide real-time traffic information. Thanks to the advances of information security and digital convergence technologies, the virtual systems become stable and secure. In this paper we have developed the virtual Telematics systems that can serve as a guideline for other virtual systems.