Virtualization is a key technology that powers cloud computing platforms such as Amazon EC2. Virtual machine (VM) consolidation, where multiple VMs share a physical host, has seen rapid adoption in practice, with increasingly large numbers of VMs per machine and per CPU core. Our investigations, however, suggest that the increasing degree of VM consolidation has serious negative effects on the VMs’ TCP performance. As multiple VMs share a given CPU, the scheduling latencies, which can be in the order of tens of milliseconds, substantially increase the typically submillisecond round-trip times (RTTs) for TCP connections in a datacenter, causing significant degradation in throughput. In this article, we propose a lightweight solution, called vPRO, that (a) offloads the VM’s TCP congestion control function to the driver domain to improve TCP transmit performance; and (b) offloads TCP acknowledgment functionality to the driver domain to improve the TCP receive performance. Our evaluation of a vPRO prototype on Xen suggests that vPRO substantially improves TCP receive and transmit throughputs with minimal per-packet CPU overhead. We further show that the higher TCP throughput leads to improvement in application-level performance, via experiments with Apache Olio, a Web 2.0 cloud application, and Intel MPI benchmark.

中文翻译：

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协议责任卸载以提高虚拟化环境中的 TCP 吞吐量

虚拟化是支持 Amazon EC2 等云计算平台的一项关键技术。多个虚拟机共享一个物理主机的虚拟机 (VM) 整合在实践中得到了迅速采用，每台机器和每个 CPU 内核的虚拟机数量越来越多。然而，我们的调查表明，VM 整合程度的提高对 VM 的 TCP 性能有严重的负面影响。由于多个虚拟机共享一个给定的 CPU，调度延迟（可能在几十毫秒的数量级）显着增加了数据中心中 TCP 连接的典型亚毫秒往返时间 (RTT)，从而导致吞吐量显着下降。在本文中，我们提出了一个轻量级的解决方案，称为 vPRO，(a) 将 VM 的 TCP 拥塞控制功能卸载到驱动程序域以提高 TCP 传输性能；(b) 将 TCP 确认功能卸载到驱动程序域以提高 TCP 接收性能。我们在 Xen 上对 vPRO 原型的评估表明，vPRO 以最小的每个数据包 CPU 开销显着提高了 TCP 接收和传输吞吐量。我们通过对 Apache Olio、Web 2.0 云应用程序和英特尔 MPI 基准测试的实验进一步表明，更高的 TCP 吞吐量可以提高应用程序级的性能。