XoT: A Flexible Block I/O Data Transfer Protocol for Xen

The management of I/O resources is an important part of virtualization. Although the traditional management is complex, it becomes more challenging in virtualization. There has been many researches on how to improve I/O performance or fairness on Linux using extra semantic data, unfortunately many of them are not proper for virtualization. Because of the limitation of I/O protocol, such extra data can not be transferred along with device data. This forms a semantic gap between VM and hypervisor. In this paper, we proposed Xen on Turnout (XoT), a flexible block I/O data transfer protocol for Xen. XoT makes it possible to transfer extra important I/O data across the gap. We also develop a prototype to prove the effectiveness of our protocol. Our result shows that preferential effect are well achieved for user to manage block I/O with the transferred extra data, with little performance lost.