Compile Faster: Rust Optimization Tips!

Rust is slow

Really?

Looking at 500+ crates when building a simple hello world webapp…

Visualization

知彼知己百战百胜《孙子兵法》- The art of war

Show cargo build timings

$ cargo build --timings

cargo check instead of cargo build

• skip compilation but have linting, type-checking and borrow-checking
• usually when it compiles, it works applies to check too
• alternative, use rust-analyzer LSP

Remove unused dependencies

• https://github.com/est31/cargo-udeps
• cargo install cargo-udeps
• cargo +nightly udeps

Find duplicate dependencies

• sometimes dependencies have late peer-dependencies
  • A 1.0 depends on B 1.0
  • C 1.0 depends on B 0.1
  • B 1.0 and B 0.1 both needs compilation
• find these with cargo tree --duplicates
  • contribute back to the community! benefits everyone

Replace heavy dependencies

• cargo tree and cargo bloat https://github.com/RazrFalcon/cargo-bloat
• examples
  • serde -> miniserde
  • reqwests -> ureq
  • clap -> pico-args
• going extreme, prevent dependencies on procedural macro crates

Use workspaces - split into mulitple small crates

• move one big crate into multiple small crates
• https://doc.rust-lang.org/book/ch14-03-cargo-workspaces.html

Use cargo-nextest for faster test execution

• https://nexte.st

• Up to 3× as fast as cargo test

Combine all integration tests into a single binary

• https://azriel.im/will/2019/10/08/dev-time-optimization-part-1-1.9x-speedup-65-less-disk-usage/
• create a main.rs in your test folder and add your test files as mod in there

Use a faster linker

• linux - mold

tl;dr

control your dependencies

References

• https://endler.dev/2020/rust-compile-times/