AppSteer: Framework for Improving Multicore Scalability of Network Functions via Application-aware Packet Steering

Efforts to improve multicore scalability of network functions (NFs) have traditionally focused on making network stacks scalable via partitioning TCP/IP data structures into per-core slices and ensuring flow-to-core affinity, leading to elimination of locking in the network stack while processing an incoming packet. But the above techniques fail to eliminate locking in NFs which store state at the granularity of an application-layer key that does not map to a TCP/IP flow, e.g., NFs in the 5G packet core that store state at the granularity of a mobile subscriber/user, where requests from a user could arrive over multiple flows, or requests from multiple users can arrive on a single flow. Prior work does not allow steering all traffic of a particular user to the same core for such NFs. This paper presents AppSteer, a framework that enables application-aware steering of incoming requests to cores for NFs running on the Linux kernel, in order to localize the requests of a given application-layer entity (e.g., mobile user) to a single core. NFs running over AppSteer can then partition their state into per-core slices and access it in a lockfree manner, leading to better multicore scalability. We evaluate AppSteer by building lockfree versions of production-grade 5G core NFs running on top of AppSteer and show that they have 15–18% higher throughput at 16 cores when compared to their locking-based counterparts.