scx-upstream/services/README.md

A Quick Start Guide

This guide provides instructions for running the SCX schedulers as a systemd service and checking its logs.

Getting Started

At the very beginning, configure the /etc/default/scx file:

• in the SCX_SCHEDULER variable, select the scheduler you are interested in

• in the SCX_FLAGS variable, specify the flags you want to add. To do this, execute and read what flags you can add.

scx_SCHEDNAME --help

To start the SCX scheduler at boot, you need to run the systemd service as root. Here are the steps:

• Enable the service:

systemctl enable scx.service

• Start the service:

systemctl start scx.service

Alternatively, you can use a shortened version of these commands:

systemctl enable --now scx.service

• To check the status of the service, use the following command:

systemctl status scx.service

Override global configuration

It is possible to override the global scx settings using systemd environment variables SCX_SCHEDULER_OVERRIDE and SCX_FLAGS_OVERRIDE.

Example:

systemctl set-environment SCX_SCHEDULER_OVERRIDE=scx_rustland
systemctl set-environment SCX_FLAGS_OVERRIDE="-s 10000"
systemctl restart scx

If you want to restore the default value from the /etc/default/scx file execute:

systemctl unset-environment SCX_SCHEDULER_OVERRIDE
systemctl unset-environment SCX_FLAGS_OVERRIDE
systemctl restart scx

Checking Journald Logs

The SCX schedulers do not log to the default journald namespace. Instead, they save logs in a dedicated sched-ext namespace. This is where you should look for information about possible errors.

• To view the logs, use the following command:

journalctl --namespace=sched-ext

• To find logs from another system startup and identify when a potential error might have occurred, use:

journalctl --namespace=sched-ext --list-boots

• To verify the amount of space taken up by the logs, use:

journalctl --namespace=sched-ext --disk-usage