Research And Optimization Of Virtual Network Controller Model Of Xen VMX

With the development of network,the need for software compatibility is growing, and the research of virtual machine has entered into a glorious time. Virtualization technology could be divided into two kinds: para-virtualization and full-virtualization. Virtual machines which use para-virtualization need to modify the OS kernels operating on them. They have high performance. But the modification of the OS kernel will lead to the low compatibility of virtual machines. Virtual machines which use full-virtualization don't need to modify the OS kernels operating on them. They have high compatibility. They can be applied to Windows OS and Linux OS. But the performance regression is great.Xen, which is led by network laboratory of University of Cambridge, is an excellent open source virtual machine solution for x86 architecture. At first, it was based on para-virtualization, and had high performance. However, the full-virtualization solution of Xen is difficult. VT-x technology, which was introduced by Intel at 2005, gave full consideration for virtual machine support. It greatly improved the flexibility of VMM, and brought Xen the opportunity of applying full-virtualization. Right now the support for VT-x has been part of Xen3.0. And it gives Xen higher compatibility.But the performance of full-virtualization Xen is low, especially the rather weak I/O part. Full-virtualization Xen uses device model as access interface to provide the access to physical device for virtual machine. Device model emulates PC platform device. It is a software model which emulates all the hardware level programming interfaces, so as to make an unmodified device driver available in using the interfaces to do I/O operations.This thesis chose Ne2000 virtual network controller as the study object, and further studied and analyzed virtual device model in depth. Ne2000 is a network controller simpler in function, so that the theory and implementation of Ne2000 virtual network controller can be understood easily. And this can also help us understand theory and implementation of other virtual network controllers and other virtual device models.This thesis centers on a detailed study and analysis on the architecture and implementation theory of Ne2000 network controller and Ne2000 virtual network controller. Based on the analysis of model and experimental data, this thesis puts forward the performance bottleneck of virtual model, which is frequent switches between Hypervisor, Domain0 and DomainU, caused by I/O requests. Hence this thesis illustrates a solution of putting the status information of Ne2000 virtual network controller into I/O shared page, so that Hypervisor and Domain0 can access to it directly, which will promote the performance.This thesis describes the implementation of improved virtual model, and analyzes the new flows of I/O request and interrupt event. Based on the experiment analysis, the performance of the improved virtual model is very excellent. The improvement can also be implemented in other virtual network controllers and other virtual devices. And to analyze the switch between Hypervisor and DomainU will be our future work.