A Virtual Time System for OpenVZ-Based Network Emulations
A Virtual Time System for OpenVZ-Based Network Emulations
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DOI：
10.1109/pads.2011.5936745
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发表时间：
2011-06
期刊：
影响因子：
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通讯作者：
Yuhao Zheng;D. Nicol
中科院分区：
文献类型：
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作者：
Yuhao Zheng;D. Nicol
由于在实际网络上探索新想法的成本和复杂性，仿真和模拟通常用于研究通信网络的行为。执行真实的代码的仿真具有高功能保真度，但可能不具有高时间保真度，因为虚拟机通常使用其主机的时钟。主机序列化多个虚拟机的执行，并且它们的交互上的时间戳反映这种序列化。在本文中，我们提高时间保真度的OS级虚拟化系统OpenVZ给每个虚拟机自己的虚拟时钟。其核心思想是稍微修改OpenVZ和OpenVZ计数器，以便测量虚拟机在计算中使用的时间（作为虚拟执行时间的基础），并让Linux向虚拟机返回虚拟时间，但向其他进程返回普通的挂钟时间。我们的系统模拟仿真进程之间的通信网络的功能和时间行为，并控制整个系统的虚拟时间的推进。我们评估我们的系统对基线的实际无线网络测量，并观察到高的时间精度。此外，我们表明，我们的系统的实施开销低至3%。我们的研究结果表明，这是可能的，有一个网络模拟器驱动的真实的工作负载，使其仿真主机的时间精度。
Simulation and emulation are commonly used to study the behavior of communication networks, owing to the cost and complexity of exploring new ideas on actual networks. Emula-tions executing real code have high functional fidelity, but may not have high temporal fidelity because virtual machines usually use their host's clock. A host serializes the execution of multiple virtual machines, and time-stamps on their interactions reflect this serialization. In this paper we improve temporal fidelity of the OS level virtualization system OpenVZ by giving each virtual machine its own virtual clock. The key idea is to slightly modify the OpenVZ and OpenVZ schedulers so as to measure the time used by virtual machines in computation (as the basis for virtual execution time) and have Linux return virtual times to virtual machines, but ordinary wall clock time to other processes. Our system simulates the functional and temporal behavior of the communication network between emulated processes, and con-trols advancement of virtual time throughout the system. We evaluate our system against a baseline of actual wireless network measurements, and observe high temporal accuracy. Moreover, we show that the implementation overhead of our system is as low as 3%. Our results show that it is possible to have a network simulator driven by real workloads that gives its emulated hosts temporal accuracy.