[网络领域顶会追踪系列#20][NSDI'22]Justitia: 在硬件内核旁路网络上的软件多租户

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Justitia: Software Multi-Tenancy in Hardware Kernel-Bypass Networks

背景

内核旁路网络（Kernel-Bypass Network, KBN）正在成为现代数据中心的新标准。基于硬件的KBN将所有的内核数据面任务卸载至专门的网卡，以实现比基于软件的KBN更好的延迟和CPU效率，但是它也剥夺了操作员对网络共享策略的控制权。

挑战

在多租户硬件KBN上提供策略支持带来了独特的挑战---即，保留极低的延迟和低CPU开销、找到一个定义较好的调节点、重新思考流量整形器。

工作

提出了Justitia，在三个核心设计方面来解决这些挑战：

• 使用消息级别的整形来将连接分离
• 基于发送端的资源调解，以及接收端的更新
• 被动延迟监控

使用延迟目标作为它的旋钮（knob），Justitia支持多租户策略，例如可预测延迟和公平/加权资源分配。

实验

仿真结果表明，Justitia可以在利用率轻微下降的情况下，高效地对延迟敏感型应用进行隔离，并且能保证其余的吞吐和带宽没有被不公平的对待。

原文摘要

Kernel-bypass networking (KBN) is becoming the new norm in modern datacenters. While hardware-based KBN offloads all dataplane tasks to specialized NICs to achieve better latency and CPU efficiency than software-based KBN, it also takes away the operator’s control over network sharing policies. Providing policy support in multi-tenant hardware KBN brings unique challenges – namely, preserving ultra-low latency and low CPU cost, finding a well-defined point of mediation, and rethinking traffic shapers. We present Justitia to address these challenges with three key design aspects: (i) Split Connection with message-level shaping, (ii) sender-based resource mediation together with receiver-side updates, and (iii) passive latency monitoring. Using a latency target as its knob, Justitia enables multi-tenancy policies such as predictable latencies and fair/weighted resource sharing. Our evaluation shows Justitia can effectively isolate latency-sensitive applications at the cost of slightly decreased utilization and ensure that throughput and bandwidth of the rest are not unfairly penalized.