Switcheroo Rust Port

A Rust port of the original switcheroo-control daemon and CLI tool by Bastien Nocera.

From a switcheroo-control man page:

switcherooctl is the command-line interface for switcheroo-control, a daemon that manages hybrid graphics on Linux laptops with multiple GPUs. It provides a simple way to list available graphics adapters and launch applications on a specific GPU.

On hybrid graphics systems with both integrated (power-efficient) and discrete (high-performance) GPUs, applications default to the integrated GPU. Using switcherooctl, you can run specific applications on the discrete GPU for better graphics performance.

This port uses the udev crate for GPU monitoring, combined with the nix crate for low-level ioctl driver queries (amdgpu, i915, nouveau, and xe drivers) to determine whether a card is discrete or integrated.

It reimplements the standard net.hadess.SwitcherooControl interface using the zbus crate.

switcherooctl provides a user-friendly CLI via the clap crate, including implicit subcommands which are also present in the original project. The daemon likewise uses clap for its own --replace flag.

Also, just like the original project, it includes a regex-based cleanup module to prettify GPU information before it is published over D-Bus

Workspace Members

Crate	Description
switcheroo-daemon	Background system service that monitors hardware and exposes it over D-Bus
switcherooctl	CLI utility used to list GPUs and launch binaries using a specific GPU
switcheroo-common	Shared types, serialization/deserialization logic and D-Bus definitions

Architecture

flowchart TB
    User((User))

    subgraph Userspace [Userspace Context]
        CLI(switcherooctl)
        Daemon(switcheroo-daemon)
        DBus{{D-Bus System Bus}}
        TargetApp[[Target Application]]
    end

    subgraph OS_Kernel [OS & Kernel Interface]
        subgraph UdevSub [udev Subsystem]
            Udev[udev crate]
            LibUdev[libudev C FFI]
        end

        subgraph IOCTL_Sub [DRM Subsystem]
            DRM_Nodes[(/dev/dri/render*)]
            Drivers[/amdgpu, i915, xe, nouveau, nvidia/]
        end
    end

    User -->|Runs| CLI
    
    CLI -->|Queries GPUs| DBus
    DBus <-->|net.hadess.SwitcherooControl| Daemon
    DBus -->|GPU info & env| CLI
    
    CLI -.->|Spawns with env vars| TargetApp
    
    Daemon -->|Queries GPUs & watch events| Udev
    Udev -->|GPUs info & events| Daemon
    
    Daemon -->|switcheroo-discrete-gpu tag check| LibUdev
    LibUdev -->|is_discrete| Daemon
    
    Daemon -->|IOCTL probe| DRM_Nodes
    DRM_Nodes -->|VRAM / LMEM status| Daemon
    
    DRM_Nodes --- Drivers
    TargetApp -.->|Render offload| Drivers

Loading

Installation

Ensure you have the libudev library installed where it can be found by pkg-config.

Example:

sudo apt-get install libudev-dev    # Debian-based Linux distributions
sudo zypper install systemd-devel   # openSUSE/SLE
sudo dnf install systemd-devel      # Fedora/RHEL

You can either compile a release build using Cargo:

git clone https://github.com/LuMarans30/switcheroo-control-rs
cd switcheroo-control-rs
cargo build --release

OR

Install them from crates.io:

cargo install switcherooctl switcheroo-daemon

System Service Installation (Optional)

You can install the provided Systemd and D-Bus configuration files to automatically start the daemon on boot as a service:

sudo cp ./data/switcheroo-daemon.service /usr/lib/systemd/system/
sudo cp ./data/net.hadess.SwitcherooControl.conf /usr/share/dbus-1/system.d/
sudo cp ./target/release/switcheroo-daemon /usr/libexec

sudo systemctl daemon-reload
sudo systemctl enable --now switcheroo-daemon

Usage

To test the daemon manually, stop the original system service first to avoid D-Bus conflicts:

sudo systemctl stop switcheroo-control
sudo env "PATH=$PATH" switcheroo-daemon # or sudo ./target/release/switcheroo-daemon

Tip

The daemon supports a --replace flag to replace an already running instance. Without it, the daemon will exit immediately if another instance holds the bus name.

You can now use the CLI tool:

switcherooctl help

Usage: switcherooctl [OPTIONS] [COMMAND]

Commands:
  list    List the known GPUs
  launch  Launch a command on a specific GPU
  help    Print this message or the help of the given subcommand(s)

Options:
  -g, --gpu <GPU>
  -h, --help       Print help

Example

Launch glmark2's refract benchmark on a discrete GPU:

switcherooctl launch --gpu 1 glmark2 -b refract

For simplicity, you can also omit subcommands:

switcherooctl            # "switcherooctl list"
switcherooctl <program>  # "switcherooctl launch <program>" 

Performance

The Rust CLI shows significant performance gains over the Python CLI by eliminating the interpreter startup overhead. The Rust daemon has roughly the same performance and memory footprint as the original C daemon.

Below are some benchmarks using hyperfine. To demonstrate full interoperability, I tested the clients against both daemons.

Using the switcheroo-daemon

List GPUs:

~/projects/switcheroo-control-rs > hyperfine --warmup 10 -N \
  'switcherooctl list' \
  './target/release/switcherooctl list'
Benchmark 1: switcherooctl list
  Time (mean ± σ):     138.9 ms ±  34.0 ms    [User: 111.2 ms, System: 26.4 ms]
  Range (min … max):   104.5 ms … 227.5 ms    19 runs

Benchmark 2: ./target/release/switcherooctl list
  Time (mean ± σ):       5.6 ms ±   1.1 ms    [User: 1.7 ms, System: 5.7 ms]
  Range (min … max):     3.4 ms …  11.1 ms    711 runs

Summary
  ./target/release/switcherooctl list ran
   24.62 ± 7.74 times faster than switcherooctl list

Launch glxinfo:

~/projects/switcheroo-control-rs > hyperfine --warmup 10 --min-runs 50 -N \
  'switcherooctl launch glxinfo -B' \
  './target/release/switcherooctl launch glxinfo -B'
Benchmark 1: switcherooctl launch glxinfo -B
  Time (mean ± σ):     262.3 ms ±  31.8 ms    [User: 122.3 ms, System: 133.1 ms]
  Range (min … max):   221.5 ms … 364.4 ms    50 runs

Benchmark 2: ./target/release/switcherooctl launch glxinfo -B
  Time (mean ± σ):     146.0 ms ±  12.6 ms    [User: 34.0 ms, System: 107.4 ms]
  Range (min … max):   123.0 ms … 172.8 ms    50 runs

Summary
  ./target/release/switcherooctl launch glxinfo -B ran
    1.80 ± 0.27 times faster than switcherooctl launch glxinfo -B

Using the original switcheroo-control service

List GPUs:

~/projects/switcheroo-control-rs > hyperfine --warmup 10 -N \
  'switcherooctl list' \
  './target/release/switcherooctl list'
Benchmark 1: switcherooctl list
  Time (mean ± σ):     153.8 ms ±  45.9 ms    [User: 120.3 ms, System: 32.2 ms]
  Range (min … max):   102.7 ms … 236.2 ms    27 runs

Benchmark 2: ./target/release/switcherooctl list
  Time (mean ± σ):       5.9 ms ±   1.1 ms    [User: 1.8 ms, System: 5.9 ms]
  Range (min … max):     3.5 ms …  12.6 ms    478 runs

Summary
  ./target/release/switcherooctl list ran
   26.01 ± 9.07 times faster than switcherooctl list

Launch glxinfo:

~/projects/switcheroo-control-rs > hyperfine --warmup 10 --min-runs 50 -N \
  'switcherooctl launch glxinfo -B' \
  './target/release/switcherooctl launch glxinfo -B'
Benchmark 1: switcherooctl launch glxinfo -B
  Time (mean ± σ):     270.2 ms ±  40.9 ms    [User: 130.1 ms, System: 133.1 ms]
  Range (min … max):   214.3 ms … 359.0 ms    50 runs

Benchmark 2: ./target/release/switcherooctl launch glxinfo -B
  Time (mean ± σ):     142.1 ms ±  11.3 ms    [User: 31.2 ms, System: 106.4 ms]
  Range (min … max):   119.5 ms … 177.0 ms    50 runs

Summary
  ./target/release/switcherooctl launch glxinfo -B ran
    1.90 ± 0.33 times faster than switcherooctl launch glxinfo -B

Memory footprint

The Rust CLI also has a much smaller memory footprint:

~/projects/switcheroo-control-rs > /usr/bin/time -v ./target/release/switcherooctl list 2>&1 | grep "Maximum resident set size"
        Maximum resident set size (kbytes): 6024

~/projects/switcheroo-control-rs > /usr/bin/time -v switcherooctl list 2>&1 | grep "Maximum resident set size"
        Maximum resident set size (kbytes): 31740

The daemons have roughly the same memory footprint:

~/projects/switcheroo-control-rs > ps -o pid,rss,comm -C switcheroo-control
    PID   RSS COMMAND
 117108  9056 switcheroo-cont

~/projects/switcheroo-control-rs > ps -o pid,rss,comm -C switcheroo-daemon
    PID   RSS COMMAND
 133147  9380 switcheroo-daem

License

The project is licensed under GPL-3.0-or-later to match upstream.