Here's a detailed comparison table of the four strategies for running a Rust binary on boot, covering boot latency, complexity, performance, and other relevant metrics:
π Comparison Table: Rust in Initramfs vs Kernel Module vs Built-in vs No Kernel
| Strategy | Boot Time | Latency to Rust Code | Complexity | Syscall/Kernel Dependency | Runtime Flexibility | Performance Potential | Notes |
|---|---|---|---|---|---|---|---|
π¦ Rust Binary in initramfs (as /init) | ~50β200 ms | ~10β30 ms | π΅ Low | β Full Linux userspace | β High | βͺοΈ Moderate | Most practical setup; just add binary to initramfs |
| π¨ Rust as a Kernel Module | ~30β100 ms | ~1β5 ms | π‘ Medium | β Partial Kernel Dep | βͺοΈ Limited | π‘ High | Requires modprobe or boot-time module loading |
| π₯ Rust Built into Kernel (built-in) | ~5β50 ms | ~100β500 ΞΌs | π΄ High | β No userspace required | β Fixed binary | π΄ Very High | Requires kernel recompilation and linking Rust code in-tree |
| β«οΈ Bare Metal Rust (No Linux Kernel) | ~<5 ms (custom) | ~10β100 ΞΌs | β«οΈ Very High | β None | β None | π’ Max Possible | Real-time control, full custom OS (ex: no_std, custom bootloader) |
π§ Key Takeaways
- Rust in initramfs: Great balance of performance and simplicity.
- Kernel module: Gains early access to hardware and kernel functions, but needs root + careful loading.
- Built-in: Latency and cold-start optimized, but tightly coupled to Linux internals.
- Bare-metal: Ultimate control and speed, but youβre writing your own OS.
Let me know if you want a real-world example of compiling Rust into the kernel, or a minimal bootable initramfs with your Rust binary only β whichever path you're targeting.