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scx/scheds/rust
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David Vernet c6ada251ef scx_rustland: use custom pcpu DSQ instead of SCX_DSQ_LOCAL{_ON} 
We still don't have a reliable and non-racy way to manage cpumasks from
the user-space scheduler, so it is quite hard for the scheduler to
enforce the proper CPU affinity behavior.

Despite checking the cpumask in the BPF part, tasks may still be
assigned to a CPU that they cannot use, triggering scheduler errors.

For example, it is really easy to crash the scheduler with a simple CPU
affinity stress test (`stress-ng --race-sched 8 --timeout 5`):

  14:51:28 [WARN] FAIL: SCX_DSQ_LOCAL[_ON] verdict target cpu 1 not allowed for stress-ng-race-[567048] (err=1024)

To prevent this issue from happening, create custom DSQ for each CPU
available in the system and use these per-CPU DSQs to dispatch all the
tasks processed by the user-space scheduler, including the user-space
scheduler itself.

Then consume the these DSQs from the .dispatch() callback of the
respective CPU, to transfer all the tasks to the consuming CPU's local
DSQ, preventing the cpumask race condition encountered using
SCX_DSQ_LOCAL_ON.

With this patch applied the `stress-ng --race-sched N` stress test can
be executed successfully (even with large values of N) without causing
the scheduler to crash.

Signed-off-by: David Vernet <void@manifault.com>
[ arighi: kick target cpu to improve responsiveness, update comments ]
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
2024-01-21 15:47:35 +01:00
..
scx_layered Update descriptions in cargo toml files 2024-01-19 18:19:46 -08:00
scx_rustland scx_rustland: use custom pcpu DSQ instead of SCX_DSQ_LOCAL{_ON} 2024-01-21 15:47:35 +01:00
scx_rusty Update descriptions in cargo toml files 2024-01-19 18:19:46 -08:00
meson.build scx_rustland: rename from scx_rustlite 2023-12-22 00:20:14 +01:00
README.md Add README files for each rust scheduler 2024-01-04 07:35:44 -08:00

README.md

RUST SCHEDULERS

Introduction

This directory contains schedulers with user space rust components.

The README in each scheduler directory provides some background and describes the types of workloads or scenarios they're designed to accommodate. For more details on any of these schedulers, please see the header comment in their main.rs or *.bpf.c files.

Schedulers