- 學位論文
Network performance isolation for virtual machines
Network performance isolation for virtual machines
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並列摘要
Cloud computing is a new computing paradigm that aims to transform computing services into a utility, just as providing electricity in a “pay-as-you-go” manner. Data centers are increasingly adopting virtualization technology for the purpose of server consolidation, flexible resource management and better fault tolerance. Virtualization-based cloud services host networked applications in virtual machines (VMs), with each VM provided the desired amount of resources using resource isolation mechanisms. Effective network performance isolation is fundamental to data centers, which offers significant benefit of performance predictability for applications. This research is application-driven. We study how network performance isolation can be achieved for latency-sensitive cloud applications. For media streaming applications, network performance isolation means both predicable network bandwidth and low-jittered network latency. The current resource sharing methods for VMs mainly focus on resource proportional share, whereas ignore the fact that I/O latency in VM-hosted platforms is mostly related to resource provisioning rate. The resource isolation with only quantitative promise does not sufficiently guarantee performance isolation. Even the VM is allocated with adequate resources such as CPU time and network bandwidth, problems such as network jitter (variation in packet delays) can still happen if the resources are provisioned at inappropriate moments. So in order to achieve performance isolation, the problem is not only how many/much resources each VM gets, but more importantly whether the resources are provisioned in a timely manner. How to guarantee both requirements to be achieved in resource allocation is challenging. This thesis systematically analyzes the causes of unpredictable network latency in VM-hosted platforms, with both technical discussion and experimental illustration. We identify that the varied network latency is jointly caused by VMM CPU scheduler and network traffic shaper, and then address the problem in these two parts. In our solutions, we consider the design goals of resource provisioning rate and resource proportionality as two orthogonal dimensions. In the hypervisor, a proportional share CPU scheduler with soft real-time support is proposed to guarantee predictable scheduling delay; in network traffic shaper, we introduce the concept of smooth window to smooth packet delay and apply closed-loop feedback control to maintain network bandwidth consumption. The solutions are implemented in Xen 4.1.0 and Linux 2.6.32.13, which are both the latest versions when this research was conducted. Extensive experiments have been carried out using both real-life applications and low-level benchmarks. Testing results show that the proposed solutions can effectively guarantee network performance isolation, by achieving both predefined network bandwidth and low-jittered network latency.