scx-upstream/scheds/rust/scx_layered
David Vernet 56ff3437a2
layered: Set layered cpumask in scheduler init call
In layered_init, we're currently setting all bits in every layers'
cpumask, and then asynchronously updating the cpumasks at later time to
reflect their actual values at runtime. Now that we're updating the
layered code to initialize the cpumasks before we attach the scheduler,
we can instead have the init path actually refresh and initialize the
cpumasks directly.

Signed-off-by: David Vernet <void@manifault.com>
2024-02-21 15:38:23 -06:00
..
src layered: Set layered cpumask in scheduler init call 2024-02-21 15:38:23 -06:00
.gitignore Restructure scheds folder names 2023-12-17 13:14:31 -08:00
build.rs Restructure scheds folder names 2023-12-17 13:14:31 -08:00
Cargo.toml [scx_layered] downgrade prometheus-client 2024-01-31 04:36:01 -08:00
LICENSE Restructure scheds folder names 2023-12-17 13:14:31 -08:00
meson.build Restructure scheds folder names 2023-12-17 13:14:31 -08:00
README.md Add README files for each rust scheduler 2024-01-04 07:35:44 -08:00
rustfmt.toml Restructure scheds folder names 2023-12-17 13:14:31 -08:00

scx_layered

This is a single user-defined scheduler used within sched_ext, which is a Linux kernel feature which enables implementing kernel thread schedulers in BPF and dynamically loading them. Read more about sched_ext.

Overview

A highly configurable multi-layer BPF / user space hybrid scheduler.

scx_layered allows the user to classify tasks into multiple layers, and apply different scheduling policies to those layers. For example, a layer could be created of all tasks that are part of the user.slice cgroup slice, and a policy could be specified that ensures that the layer is given at least 80% CPU utilization for some subset of CPUs on the system.

How To Install

Available as a Rust crate: cargo add scx_layered

Typical Use Case

scx_layered is designed to be highly customizable, and can be targeted for specific applications. For example, if you had a high-priority service that required priority access to all but 1 physical core to ensure acceptable p99 latencies, you could specify that the service would get priority access to all but 1 core on the system. If that service ends up not utilizing all of those cores, they could be used by other layers until they're needed.

Production Ready?

Yes. If tuned correctly, scx_layered should be performant across various CPU architectures and workloads.

That said, you may run into an issue with infeasible weights, where a task with a very high weight may cause the scheduler to incorrectly leave cores idle because it thinks they're necessary to accommodate the compute for a single task. This can also happen in CFS, and should soon be addressed for scx_layered.