Backdraft: a Lossless Virtual Switch that Prevents the Slow Receiver Problem
Backdraft: a Lossless Virtual Switch that Prevents the Slow Receiver Problem
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发表时间：
2022
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通讯作者：
Alireza Sanaee;Farbod Shahinfar;Gianni Antichi;Brent E. Stephens
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作者：
Alireza Sanaee;Farbod Shahinfar;Gianni Antichi;Brent E. Stephens
用于终端主机网络的虚拟交换机会在接收应用程序速度不够快而无法消耗数据包时丢弃数据包。这称为慢接收器问题，这一点很重要，因为数据包丢失会损害尾部通信延迟并浪费 CPU 周期，从而导致应用程序级性能下降。此外，解决这个问题具有挑战性，因为应用程序吞吐量在短时间内变化很大，因为它取决于工作负载、内存争用和操作系统线程调度。本文介绍了 Backdraft，一种新的无损虚拟交换机，它通过组合三个新组件来解决接收速度慢的问题：(1) 动态每流队列 (DPFQ)，以防止 HOL 阻塞并提供按需内存使用； (2)门铃队列，减少CPU开销； (3)新的覆盖网络以避免拥塞扩散。我们在 BESS 之上实现了 Backdraft，并在使用 DCTCP 和 Homa（一种最先进的拥塞控制方案）的 100 Gbps 集群上进行了实际应用实验。我们证明，具有 Backdraft 的应用程序可以在第 99 个百分位数处实现高达 20 倍的尾延迟降低。
Virtual switches, used for end-host networking, drop packets when the receiving application is not fast enough to consume them. This is called the slow receiver problem, and it is important because packet loss hurts tail communication latency and wastes CPU cycles, resulting in application-level performance degradation. Further, solving this problem is challenging because application throughput is highly variable over short timescales as it depends on workload, memory contention, and OS thread scheduling. This paper presents Backdraft, a new lossless virtual switch that addresses the slow receiver problem by combining three new components: (1) Dynamic Per-Flow Queuing (DPFQ) to prevent HOL blocking and provide on-demand memory usage; (2) Doorbell queues to reduce CPU overheads; (3) A new overlay network to avoid congestion spreading. We implemented Backdraft on top of BESS and conducted experiments with real applications on a 100 Gbps cluster with both DCTCP and Homa, a state-of-the-art congestion control scheme. We show that an application with Backdraft can achieve up to 20x lower tail latency at the 99 th percentile.