SwapCached: An Effective Method to Promote Guest Paging Performance on Virtualization Platform

With the increasing number of Internet businesses put in the data center, the great importance of server consolidation and hardware integration are highlighted. Among common hardware resources, the consolidation of memory is one of the classic problems, which has been widely studied. Some of the consolidation technologies, such as memory balloon driver and inter-VM page sharing, have been exploited in commercial virtualization software. But even with the integration of these methods, frequent disk IO introduced by paging mechanism in guest VM might also bring serious performance penalty with thrashing when guest memory usage changes dramatically. In order to reduce this unnecessary overload and guarantee the system performance, this paper proposes Swap Cached, a backend swapped page caching method. Swap Cached is designed to be able to cache the pages swapped from guest VMs in host memory to reduce the disk IO operation as well as effectively balance the memory usage between guests and host. The prototype of Swap Cached has been implemented on Xen platform using the existing memory cache software and virtualization technology. The benchmark results show that this implementation can promote the performance of the whole platform between 10% and 80% under different types of guest applications.