Enable Link-Time Optimization (LTO) and codegen-units = 1 for Release builds

[zamazan4ik]

Hi. Congratulations with the 3.0 release!

I noticed that after the Rust rewrite, in the Cargo.toml file Link-Time Optimization (LTO) for the project is not enabled. I suggest switching it on since it will reduce the binary size (always a good thing to have) and will likely improve the application's CPU performance a bit. If you want to read more about LTO and its possible modes, I recommend starting from this Rustc documentation.

I think you can enable LTO only for the Release builds so as not to sacrifice the developers' experience while working on the project, since LTO consumes an additional amount of time to finish the compilation routine. In this case, we can create a dedicated [profile.optimized-dev] profile where LTO will be disabled (so developers experience will not be affected). If we enable it on the Cargo profile level for the Release profile, users, who install the application with cargo install, will get the LTO-optimized version of the app "automatically". Actually, I can propose to use flags directly from the ripgrep profile.

Basically, it can be enabled with the following lines to the root Cargo.toml file:

[profile.release]
codegen-units = 1
lto = true
... # other flags

I have made quick tests (AMD Ryzen 9 5900x, Fedora 42, Rust 1.89, the latest version of the project at the moment, cargo build --release command) - here are the results:

• Release: 8.5 Mib, clean build time: 22s
• Release + codegen-units = 1 + Fat LTO: 6.8 Mib, clean build time: 57s

The same tests for MacBook M1 Pro, macOS, Rust 1.89:

• Release: 7.6 Mib, clean build time: 39s
• Release + codegen-units = 1 + Fat LTO: 5.6 Mib, clean build time: 1m 17s

Thank you.

[ku1ik]

Thanks. The 2 options shaved off exactly 2MB of the binary on my NixOS system, nice!

asciinema/asciinema@71e54b2

[ku1ik]

Although the build time is brutal now /m\

[zamazan4ik]

Yeah, that's the price. However, in my opinion this tradeoff is completely fine since we enable it only for Release builds :) So users can build the application once and wait for the build more, but after that they will get the more optimized binary that will be stored on their machines for much longer time.