scx_loader & scxctl

scx_loader is a system daemon and DBus-based loader for sched_ext schedulers. scxctl is the command-line client for interacting with the loader, allowing users to switch schedulers, modes, and arguments dynamically.

Both tools were originally part of the main sched-ext/scx repository and are now developed independently.

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✨ Features

• Systemd service: scx_loader.service
• DBus interface for scheduler management (org.scx.Loader)
• CLI client scxctl for manual control
• Multiple runtime modes (Auto, Gaming, LowLatency, PowerSave, Server)
• Per-scheduler arguments via TOML configuration
• Installable directly from crates.io or buildable from source

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🚀 Installation

1. Install from crates.io

cargo install scx_loader
cargo install scxctl

The binaries will be installed in ~/.cargo/bin. Ensure this directory is in your PATH:

export PATH="$HOME/.cargo/bin:$PATH"

2. Build from source

Clone and compile the repository:

git clone https://github.com/sched-ext/scx-loader.git
cd scx-loader

# Build optimized binaries
cargo build --release

Then install them system-wide:

sudo install -Dm755 target/release/scx_loader /usr/bin/
sudo install -Dm755 target/release/scxctl /usr/bin/

or

sudo find target/release \
    -maxdepth 1 -type f -executable ! -name '*.so' \
    -exec install -Dm755 -t /usr/bin/ {} +

Make sure you have also installed the necessary configuration files.

sudo install -Dm644 services/scx_loader.service \
    -t /usr/lib/systemd/system/
sudo install -Dm644 services/org.scx.Loader.service \
    -t /usr/share/dbus-1/system-services/
sudo install -Dm644 configs/org.scx.Loader.conf \
    -t /usr/share/dbus-1/system.d/
sudo install -Dm644 configs/scx_loader.toml \
    /usr/share/scx_loader/config.toml

3. Install with xtask

Alternatively, you can use xtask to install the required files:

cargo xtask install

Environment Variables for xtask

The xtask install command respects several environment variables for customizing installation paths, which is useful for packaging by distributions:

• VENDOR_PREFIX: Overrides the default /usr prefix for installation paths. (e.g., /usr/local)
• VENDOR_DATADIR: Overrides the default /usr/share for data files.
• VENDOR_SYSCONFDIR: Overrides the default /etc for configuration files.
• VENDOR_LIBDIR: Overrides the default $VENDOR_PREFIX/lib for library files.

Additionally, the --destdir flag can be used with xtask install to create package:

cargo xtask install --destdir $pkgdir

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⚙️ Configuration

scx_loader reads a TOML configuration file that defines the default scheduler and mode, along with per-scheduler arguments.

Example configuration:

# This field specifies the scheduler that will be started automatically when scx_loader starts (e.g., on boot).
default_sched = "scx_cosmos"

# This field specifies the mode which will be used when scx_loader starts (e.g., on boot).
default_mode = "Auto"

# This "structure" allows configuring flags for each scheduler mode of particular scx scheduler
#[scheds.'scheduler']
#auto_mode = []
#gaming_mode = []
#lowlatency_mode = []
#powersave_mode = []
#server_mode = []

Configuration lookup order

scx_loader searches configuration files in the following order:

1. /etc/scx_loader/config.toml
2. /etc/scx_loader.toml
3. $VENDORDIR/scx_loader/config.toml
4. $VENDORDIR/scx_loader.toml

$VENDORDIR defaults to /usr/share, but distributions may override it.

This environment variable applies only at build time, so developers or distributions must set it before building.

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🧩 Systemd Integration

The package provides a systemd service unit for automatic startup:

sudo systemctl enable --now scx_loader.service

You can check its status using:

systemctl status scx_loader.service

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💡 Using scxctl

See: scxctl

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🧠 Troubleshooting

📖 Full usage guide available in the CachyOS wiki.

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🤝 Contributing

Pull requests and discussions are welcome! Follow Rust coding conventions and include descriptive commit messages. Bug reports and proposals can be submitted in the scx-tools issue tracker.

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