scx_loader & scxctl & scxtui

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. scxtui is an interactive terminal user interface for managing schedulers, inspecting the current loader state, and viewing recent scheduler logs.

These 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 scriptable and manual control
• Interactive terminal client scxtui for scheduler management and status inspection
• Start, switch, stop, restart, and restore schedulers from the terminal UI
• View the active scheduler, mode, arguments, and recent journal entries
• 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
cargo install scxtui

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/
sudo install -Dm755 target/release/scxtui /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/org.scx.Loader.xml \
    -t /usr/share/dbus-1/interfaces/
sudo install -Dm644 configs/org.scx.Loader.policy \
    -t /usr/share/polkit-1/actions/
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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🖥️ Using scxtui

Launch the terminal interface with:

scxtui

scxtui provides an interactive view of the schedulers exposed by the active backend. It can be used to:

• inspect the currently running scheduler, mode, and arguments;
• select and start or switch schedulers and modes;
• stop, restart, or restore the configured default scheduler;
• refresh the scheduler list and runtime state;
• inspect recent scx_loader journal entries.

The interface discovers loader capabilities at runtime and degrades gracefully when optional D-Bus methods are unavailable.

See: scxtui

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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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