Introduction to eBPF Qdisc and Use Cases – Amery Hung, ByteDance
eBPF queueing discipline (qdisc) is a newly proposed, programmable yet generic packet scheduler. Unlike designs that rely on certain scheduling primitives (e.g., Push-In-First-Out, Eiffel), eBPF grants developers more flexibility by allowing them to implement qdiscs using eBPF. It aims to facilitate innovation in packet scheduling by reducing the complexity of developing and deploying qdiscs. Traditionally, the process requires a developer to write a qdisc kernel module from scratch. In addition, it needs to be configured correctly both in terms of the attribute and the hierarchy when used with other qdiscs. eBPF qdisc solves the problems by letting the developer only deal with the core enqueue and dequeue operations. It is also possible to encapsulate hierarchical queues with user defined objects using eBPF. In this talk, we will introduce the design of eBPF qdisc. This includes four eBPF programs of a new type and new kernel functions (kfunc) available to them. Then, we will demonstrate how to write a qdisc using eBPF. Finally, we will showcase three use cases of eBPF qdiscs.
