A Survey on I/O Virtualization and Optimization

This paper surveys virtualization of I/O devices, which is one of the most difficult parts in system virtualization. Current technologies of virtualizing I/O devices include full virtualization, paravirtualization, software emulation and VMM-bypass direct I/O. Optimizations are also done to improve the performance of each technology. Most optimizations used paravirtualization technology for reference. VMM-bypass direct I/O performs the best performance, but the VM direct-access I/O devices is difficult to be migrated, for it is hard to capture the states of the devices without VMM interference. An ideal approach is still required, and all the optimizations to the other approaches can be used for reference. We evaluated I/O performance in KVM and proposed some optimizations to improve KVM.