72 research outputs found
Guest Editor's introduction to the special issue on "IEEE Workshop on Emerging Technologies for Next Generation Grids 2005"
No full textPredicting parallel applications performance on non-dedicated cluster platforms
No full textWe address the problem of performance prediction for parallel programs executed on clusters of heterogeneous workstations on which resource contention is present. We develop a methodology for the construction of performance models whose analysis allows the estimation of the execution time of these programs. We use Timed Petri Nets to represent the behavior of parallel programs, and a contention model based on queueing theory to quantify the effects of resource contention on the execution time of the application processes. Our methodology is demonstrated through the construction of the model of an example program, which is also used to validate the predictions against measured execution times obtained by executing the program on two different clusters of workstations
A Comparative Evaluation of Implicit Coscheduling Strategies for Networks of Workstation
No full textImplicit coscheduling strategies enable parallel applications to dynamically share the machines in a Network of Workstation (NOW) with interactive, CPU and IO-bound sequential jobs. In this paper we present a simulation study that compares 12 coscheduling strategies in terms of their impact on the performance of parallel and sequential applications executed simultaneously on a NOW. Our results show that the coscheduling strategy has a strong impact on the performance of the applications (both parallel and sequential) composing the workload, and that no single strategy is able to effectively handle all workloads. In spite of that, our results can be used to identify the strategy that represents the best choice for a given application class, or the best compromise for various workloads. Moreover, we show that in many cases simple strategies outperform more complex ones
Automatic Generation of GSPN Models for the Performance Evaluation of Heterogeneous Applications
No full textPerformance Modeling of Heterogeneous Distributed Applications
No full textHeterogeneous network computing allows the development of a single complex application using a distributed network of machines; these machines may differ in terms of CPU and memory capacity and/or architecture and specialized functions. In this paper we present a modeling technique, based on Generalized Stochastic Petri Nets (GSPNs), for the performance analysis of applications targeted to this class of systems (heterogeneous applications). We illustrate the use of the proposed technique by modeling and analyzing the CASA 3D-REACT heterogeneous application
Forensic Implications of Virtualization Technologies
No full textIn the recent past machine and application virtualization technologies have received a great attention from the IT community, and are being increasingly used both in the Data Center and by the end user. The proliferation of these technologies will result, in the near future, in an increasing number of illegal or inappropriate activities carried out by means of virtual machines, or targeting virtual machines, rather than physical ones. Therefore, appropriate forensic analysis techniques, specifically tailored to virtualization environments, must be developed. Furthermore, virtualization technologies provide very effective anti-forensics capabilities, so specific countermeasures have to be sought as well. In addition to the above problems, however, virtualization technologies provide also the opportunity of developing novel forensic analysis techniques for non-virtualized systems. This chapter discusses the implications on the forensic computing field of the issues, challenges, and opportunities presented by virtualization technologies, with a particular emphasis on the possible solutions to the problems arising during the forensic analysis of a virtualized system
Forensic Analysis of WhatsApp Messenger on Android Smartphones
No full textWe present the forensic analysis of the artifacts left on Android devices by WhatsApp Messenger, the client of the WhatsApp instant messaging system. We provide a complete description of all the artifacts generated by WhatsApp Messenger, we discuss the decoding and the interpretation of each one of them, and we show how they can be correlated together to infer various types of information that cannot be obtained by considering each one of them in isolation
Performance Analysis of Heterogeneous Applications using Generalized Stochastic Petri Net Models
No full textA Performance Comparison of Coscheduling Strategies for Workstation Clusters
No full textWorkstation clusters are emerging as a general-purpose computing platform for the execution of workloads comprising parallel and sequential applications. The scalability and flexibility typical of implicit coscheduling strategies makes them a very promising solution to the scheduling needs of workstation clusters. In this paper we present a simulation study that compares, for a variety of workloads (that include both parallel and sequential applications) and operating system schedulers, 12 implicit coscheduling strategies in terms of the performance they are able to deliver to applications. By using a detailed simulator, we evaluate the performance of different coscheduling alternatives for a variety of simulation scenarios, and we identify the set of strategies that deliver the best performance to all the applications composing typical cluster workloads. Moreover, we show that for schedulers providing i>immediate preemption, the best strategies are also the simplest ones to implement
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