Research On The Strategy Of I/O Bandwidth Dynamic Allocation In Xen Virtual Machines

The history of development of virtualization technology is nearly50years, andvirtual machine systems are widely used in high-performance server integration,network security, intrusion detection, cloud computing, etc. As an importantcomponent of virtual machine systems, virtual I/O has non-negligible effects on theperformance of virtual machine systems. Especially, in distributed computer systems,I/O performance is likely to be the bottleneck. At present, improving the efficiency ofvirtual machines is the main method to optimize virtual I/O performance, but theimprovement of efficiency in a mature virtual machine system is very difficult. Whenhundreds of virtual machines running on a hardware platform, obvious effects aremuch easier to access from the perspective of resources allocation optimization. Thispaper studys the strategy of I/O bandwidth dynamic allocation in Xen virtualmachines, the main contributions are as follows:First, a brief introduction of relevant knowledge and research hotspots forvirtualization technology are given, and basic methods and current research of virtualI/O optimization are described, then the split device driver model and keytechnologies in Xen virtual I/O are analyzed detailedly.Then, from the point of services, bandwidth dynamic allocation are scrutinizedfor Xen virtual I/O, and Dynamic Mapping of Virtual Link (DMVL) is proposed viathe characteristics of Xen para-virtualization mode. The paper gives theoreticalanalysis for DMVL model, and developes performance testing methods. The basicidea of DMVL is mapping a Logical Data Path (LDP) for each virtual machine, andisolating their data streams to maintain their stable bandwidth. DMVL monitorsLDP’s bandwidth globally, and allocates bandwidth fairly and dynamically for virtualmachines in the aid of adaptive adjustment mechanism. The methods to combineDMVL with Xen virtual I/O are described via the block device driver and networkdevice driver.Finally, the Xen virtual network device driver and network data packetstransmission process are analyzed in detail, detailed design for DMVL in the Xenvirtual network is implemented. A shared I/O request queue in the back-end brings theissue of fairness, so that an I/O request queue for each virtual machine is establishedto improve the independence rate of virtual machines. The paper designs a method ofshare logs to implement adaptive bandwidth adjustment mechanism, and improves the credit bandwidth limitation module as a bandwidth adjustment module via share logs.A lottery scheduling algorithm based on logs is designed for proportional fairscheduling in request queues. By analyzing and evaluating the performance comparedto Xen, the bandwidth utilization, fairness and stability of DMVL are tested under thecircumanstance of different rates, different packets length and different mixing datastreams. The result shows that the fairness and stability of DMVL improvedsignificantly; In the case of concurrent different streams, the fairness increased bymore than57%compared with Xen.