Optimizing System Services in Virtualized Machines for Improved Execution of Parallel Applications

Hardware virtualization in the x86 architecture has enabled the use of virtual machine monitors in Beowulf clusters. In turn, each application user can then run a virtual guest operating system of his/her choice. Of course virtualizing and sharing the hardware resources in a Beowulf cluster will add additional overheads that may negatively effect performance of the application. However, the use of an application specific guest operating system also permits the introduction of application specific optimizations into that guest operating system. Potentially then, even with virtualization, the overall application performance may be improved. In this paper we consider the optimization of the communication subsystem in a Linux-based Beowulf cluster. In particular, we examine and compare the communication costs between a native TCP/IP Linux host and a virtual Linux guest with the TCP/IP drivers replaced with active message drivers. Using the KVM hypervisor, we observe that TCP/IP latency is nearly doubled in the virtual guest. However, after replacing the TCP/IP drivers with GAMMA active message drivers in the virtual guest, we observe substantial reductions in the message latency over the native TCP/IP host. We believe that this result provides us evidence to continue exploring the development of a streamlined virtual host for our research with Time Warped synchronized parallel simulation.