Elixir: A High-performance and Low-cost Approach to Managing Hardware/Software Hybrid Flow Tables Considering Flow Burstiness


Yanshu Wang and Dan Li, Tsinghua University; Yuanwei Lu, Tencent; Jianping Wu, Hua Shao, and Yutian Wang, Tsinghua University


Hardware/software hybrid flow table is common in modern commodity network devices, such as NFV servers, smart NICs and SDN/OVS switches. The overall forwarding performance of the network device and the required CPU resources are considerably affected by the method of how to split the flow table between hardware and software. Previous works usually leverage the traffic skewness for flow table splitting, e.g. offloading top 10% largest flows to the hardware can save up to ~90% CPU resources. However, the widely-existing bursty flows bring more challenges to flow table splitting. In particular, we need to identify the proper flows and proper timing to exchange the flows between hardware and software by considering flow burstiness, so as to maximize the overall performance with low overhead.

In this paper we present Elixir, a high-performance and low-cost approach to managing hardware/software hybrid flow tables on commodity devices. The core idea of Elixir includes three parts, namely, combining sampling-based and counter-based mechanisms for flow rate measurement, separating the replacement of large flows and bursty flows, as well as decoupling the flow rate identification window and the flow replacement window. We have implemented Elixir prototypes on both Mellanox ConnectX-5 NIC and Barefoot Wedge100BF-32X/65X P4 Switch, with a software library on top of DPDK. Our experiments based on real-world data traces demonstrate that, compared with the state-of-the-art solutions, Elixir can save up to ~50% software CPU resources while keeping the tail forwarding latency ~97.6% lower.

NSDI '22 Open Access Sponsored by
King Abdullah University of Science and Technology (KAUST)

Open Access Media

USENIX is committed to Open Access to the research presented at our events. Papers and proceedings are freely available to everyone once the event begins. Any video, audio, and/or slides that are posted after the event are also free and open to everyone. Support USENIX and our commitment to Open Access.

@inproceedings {278334,
author = {Yanshu Wang and Dan Li and Yuanwei Lu and Jianping Wu and Hua Shao and Yutian Wang},
title = {Elixir: A High-performance and Low-cost Approach to Managing {Hardware/Software} Hybrid Flow Tables Considering Flow Burstiness},
booktitle = {19th USENIX Symposium on Networked Systems Design and Implementation (NSDI 22)},
year = {2022},
isbn = {978-1-939133-27-4},
address = {Renton, WA},
pages = {535--550},
url = {https://www.usenix.org/conference/nsdi22/presentation/wang-yanshu},
publisher = {USENIX Association},
month = apr,

Presentation Video