The Optimization Mechanism For Virtual I/O On Xen

The development of level for manufacturing Computer Hardware bring the improvement of the computer performance and made the Virtualization Technology(VT) to be the popular topic in the computer research area. Virtualization is a technology which runs different isolated OS on a physical machine. It is Virtual Machine Manager (VMM)to providing virtual hardware. VT can providing high resources utilization ratio, integrating computing environment in enterprise,etc.The Virtualization of CPU, Memery I/O divice is the one of the most important research aspects currently.Much attention has been focused on Xen-a freesoftware.The VT provides Virtual Hardware for Guest. The VMM lies between Guest and physical device, which manages the allocation of the Computer Resources and provides the isolation among Guests.With the Hardwaresupport of the Virtualization of CPU and Memery,the performance of Guest has been close to the native machine. The Virtualization of I/O device has great cost of performance because of the character of I/O device. The Virtualization of I/O is always the bottleneck of the entire Virtualization System.The improvement of Virtual I/O can effects the performance of Virtual-System which is absolutely right. In this paper,we have discussed the research situation of VT. Also we have learned the theory and mechanism of VT on Xen, especially the I/O's virtualization and VCPU schedule algorithm. We analysis the shortage of I/O virtualization model and Credit scheduler. Then we come up to the optimization of I/O request scheduling and Optimized BOOST mechanism. Both of these optimization are based on the priority of domain or I/O request itself. The optimized mechanisms have reduced the response latency of I/O request and increased the throughput of Virtual I/O. what's more, the I/O intensive domain can preempt the other domain and be scheduled first. Above all, we have optimized the Virtual I/O in two aspects, device model and the scheduling algorithm of VCPU.At last, we build the platform for virtualization to do our experiment. The result has validated the effects of Optimized Mechansim. The optimized mechanisms have reduced the response latency of I/O requests and increased the throughput of Virtual I/O and also it provide different priorities for different domains which require different I/O latency.