How Rust and eBPF Enable User‑Space Linux Schedulers: The scx_rustland Experiment

Ubuntu kernel engineer Andrea Righi used Rust to implement a new Linux scheduler called scx_rustland , which runs in user space and leverages eBPF for dynamic runtime loading.

Righi’s original idea was to hot‑plug a Linux kernel scheduler at runtime and replace it with a user‑space program, because user space offers greater flexibility and safety.

Based on this concept, Righi combined eBPF, the new sched‑ext scheduling class, and Rust on Ubuntu to create the scheduler.

eBPF is a Linux kernel technology that allows sandboxed programs to be injected from user space into the kernel.

sched‑ext is a new scheduling class in the Linux kernel that enables implementing scheduling policies as eBPF programs.

Righi chose Rust for its memory safety, zero‑cost abstractions, and strong type system, which provide significant coding flexibility and advantages.

Ubuntu has not committed to ship the scheduler as part of the distribution; Righi describes it as an experimental kernel project to explore Rust on Ubuntu and discusses the future possibility of “micro‑kernel design” using Rust and eBPF.

The scheduler benefits developers by simplifying development and can also benefit users by loading optimized schedulers based on workload or special conditions.

“We are moving toward a micro‑kernel design that could gain Linux recognition: if a user‑space scheduler crashes, tasks seamlessly fall back to the default kernel scheduler, ensuring continuous system availability without downtime.” This suggests similar approaches could be applied to other subsystems, allowing the Linux kernel to provide fully redundant and crash‑safe systems.

Related links:

GitHub pull request

Scheduler source code

Ubuntu blog article