GIT-CERCS-08-06
    Balasubramanian Seshasayee, Karsten Schwan,
    Creating Efficient Execution Platforms with V(irtualized) Services

    Virtualization is creating new opportunities for innovative uses of middleware technologies. In this paper, we present such opportunities for mobile or pervasive environments, where virtualization eff orts face challenges that include the diversity of platforms and devices present in these domains, dynamic device and resource behaviors, and the efficient use and sharing of such resources. Speci fically, we leverage middleware to signi ficantly extend virtualization technologies in terms of their efficient support for resource sharing in the presence of diversity, dynamics, and mobility. The outcome is what we term the Virtualized Services (VServices) approach to representing and using devices and resources. VServices extend the virtual device interfaces used in existing virtualization infrastructures to go beyond sharing physical devices among multiple virtual machines, to also sharing logical entities that internally use middleware to provide new services to end user applications. By using and sharing the higher level VServices abstractions instead of physical devices, opportunities are created (i) to optimize the implementations of certain services without requiring changes to VM implementations, (ii) to enhance device functionalities by combining software service implementations with the physical devices being used, again without changing the basic nature of VM-device interactions, and (iii) to emulate devices whose physical realizations may be remote or non-existent. Experimental evaluations conducted on an implementation of these concepts in the Xen virtualization infrastructure exhibit up to 50% improvements in latency as well as improved performance scalability, when compared to current Xen implementations of such devices. This paper also describes practical realization of device enhancements using VServices.