Accurate CPU Proportional Share and Predictable I/O Responsiveness for Virtual Machine Monitor: A Case Study in Xen

摘要

In cloud computing, the performance of applications is heavily dependent on resource services provided by the virtualized environment. However, in some virtualized environment, such as Xen, the accuracy of CPU proportional share and the responsiveness of I/O processing are heavily dependent on the proportion of the allocated CPU resource. In this paper, we study how inaccurate share ratio of CPU proportional share and proportion dependent responsiveness of I/O affect the performance of Xen, and discover that they lead to unstable performance and is thus not able to conform service-level agreements (SLA). We conclude that the scheduling scheme and the coarse grained time-slice are the major negative impacts on this issue. Therefore, we propose a novel scheduling scheme, named Predictable Resource Guarantee Scheduler (PRGS), that achieves accurate CPU proportional share and predictable I/O responsiveness. We implement a PRGS prototype on Xen virtualization platform and carry out a thorough evaluation via experimentation. The experimental results show that PRGS achieves accurate CPU proportional share and predictable I/O responsiveness. Also, with only slight overhead, PRGS controls PING packet delay to a specified fixed time threshold (e.g. 30 ms in our experiments).