Xen虚拟CPU空闲调度算法

An Idle Virtual CPU Scheduling Algorithm on Xen Virtual Machines

在Xen虚拟化环境下,Credit调度算法是非抢占式调度算法,当虚拟CPU空时它不会将空闲状态信息通知给Xen,因此不会放弃物理CPU的使用权.虽然已有文献提出在虚拟CPU空闲时的处理方法,但它依然存在很多问题,例如空闲虚拟CPU的空闲时间还存在浪费的现象、没有考虑特权Service OS的空闲状态和虚拟机空闲状态判断不准确等,这造成很多不必要的性能损失.针对这样的问题,在Credit算法的基础上提出了虚拟CPU空闲调度算法,虚拟CPU空闲状态接收模块接收到的虚拟CPU空闲通知,动态调整该虚拟机的虚拟CPU的credit值,并将空闲的CPU时间分配给调度队列中其他的虚拟CPU使用.同时,根据该虚拟机的虚拟CPU的平均空闲率,重新调整该虚拟机的权重,从而实现了反馈控制与虚拟机调度的动态集成,实验结果证明该调度方法使系统的整体性能得到大大提高.

In the environment of Xen virtual machines, Credit algorithm is non-preemptible. When virtual CPU is idle, it can not inform Xen of its idle state, which leads to its keeping the usage of physical CPU. Currently, the existing methods to process idle virtual CPU only paid attention to the optimization of guest OS, and neglected that of service OS. That is to say, it has three problems to optimize, such as the waste of the time of idle virtual CPU, no consideration of idle state of service OS and the inaccuracy of the judgement of virtual machine＇s idle state, which causes great much needless loss. According to the problems, an idle virtual CPU scheduling algorithm based on Credit algorithm is given. When the message of virtual CPU＇s idle state is notified by reception module of idle state of virtual CPU, virtual CPU＇s credit of virtual machine is modified dynamically, in order to allocate the reminder of idle time to other virtual machine. At the same time, the weight of virtual machine is also modified according to the virtual CPUs＇ average idle rate of the virtual machine, which realizes the dynamic integration between virtual machine＇s scheduling method and feedback control. The experiment results show that the idle virtual CPU scheduling algorithm improves greatly the performance of virtual machines.