Wei Jiang

Tsinghua University, Peping, Beijing, China

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Publications (3)0 Total impact

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    ABSTRACT: This paper describes a nested virtualization solution, which allows virtual machine monitor (VMM) with virtual machine to run within another virtual machine with low overhead. Previous nested virtualization solutions on x86 platform are mainly based on emulation, which result in poor performance and poor usability. We propose and implement NestCloud, a practical high performance nested virtualization architecture, which fully employs the hardware virtualization extensions. Furthermore, three optimizations are provided to reduce the overhead of nested guests: (1) Guest Page Fault Bypassing, which permits nested guests to handle page faults without VM Exit; (2) Virtual EPT (Extended Page Table), which eliminates unnecessary page faults introduced by shadow page table in nested VMM; (3) PV VMCS, which provides more effective VMCS accessing for nested VMM. Experimental results show that the performance of NestCloud guest is close to single level guest in both CPU-intensive and memory-intensive benchmarks. The CPU overhead is 5.22% and the memory overhead is 5.69%, which makes the nested guest of NestCloud comparable with a conventional one.
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    ABSTRACT: Multi-core architecture provides more on-chip parallelism and powerful computational capability. It helps virtualization achieve scalable performance. KVM (kernel based virtual machine) is different from other virtualization solutions which can make use of the Linux kernel components such as completely fair scheduler (CFS). However, CFS treats the KVM threads as normal tasks without considering about their unique features such as thread allocation mechanism and lock inside guest virtual machine, which may harm the KVM virtualization performance. In this paper, we analyze a phenomenon that some guest multi-threaded applications have very low performance when scheduled by CFS. As a solution to this problem, we introduce two kinds of optimizations in CFS: (1) configuration optimizations (2) lock optimizations. Our contributions are: (1) implement 5 original and 2 newest proposed optimizations in the newest Linux kernel. (2) Classify and compare them, a brief analysis is also given. They are all very simple and general to other virtual machine monitors such as Xen and schedulers as O(1). The performance of our CFS optimizations to KVM threads is measured by running some well-known benchmarks in two guest virtual machines on an 8-core server which models the real world applications. The results indicate our scheduling optimizations can improve the overall system performance. This paper can provide useful advices to KVM developers and virtualization data center administrators.
    IEEE 15th International Conference on Parallel and Distributed Systems, ICPADS 2009, 8-11 December 2009, Shenzhen, China; 01/2009
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    ABSTRACT: CPU scheduler is a very important subsystem which affects system throughput, interactivity and fairness. The development of Linux kernel is relatively fast-paced. By now, many CPU schedulers have been designed by researchers, hobbyists and kernel hackers. It is necessary to accurately compare and analyze different characteristics among these schedulers, so as to understand and design better CPU schedulers for various applications. However, researchers lack a straight-forward method to compare and analyze these CPU schedulers precisely. In this paper, we systematically analyze and measure fairness, interactivity and multi-processors performance of three schedulers: O(1), RSDL and CFS, by using micro, synthesis and real application benchmarks. They have been ported into one scheduler framework in Linux kernel-2.6.29. Experimental results show that there are notable differences in fairness and interactivity under micro benchmarks, while minor differences in synthesis and real applications. We also analyze the impact of implementations of schedulers on fairness and interactivity of applications, discuss challenges in estimating application resource requirements in different environments, and present some ideas for developing future CPU schedulers.
    01/2009; DOI:10.1109/RTCSA.2009.26

Publication Stats

20 Citations

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Institutions

  • 2009–2011
    • Tsinghua University
      • Department of Computer Science and Technology
      Peping, Beijing, China