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Discussion on: Performance Comparison, Rust vs Crystal with Redis

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tamas profile image
Tamás Szelei

Great comparison. What happens if you enable LTO in rust?

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jgaskins profile image
Jamie Gaskins Author

I'm not sure what that is. Is that the same as the --release flag?

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aidiakapi profile image
Aidiakapi

Add:

[profile.release]
lto = true

In Cargo.toml to enable it. It allows more optimizations between crates at the cost of longer compile time. Though it's unlikely to give a 2x improvement.

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tamas profile image
Tamás Szelei

Sorry, just saw your answer and after I practically typed the same. I agree that it's unlikely to give a 2x speedup.

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tamas profile image
Tamás Szelei

LTO stands for link-time optimization, which is a great feature of LLVM (thus, rustc). You can enable it in your Cargo.toml:

[profile.release]
lto = true

The above will make --release builds use "fat" LTO, meaning all dependencies and the project itself is link-time optimized (you could set it to "thin" which means LTO is only applied to the current crate).

Another option to go even further is PGO, but that is a bit more involved and I haven't tried it with rust. Here is some documentation if you are interested: doc.rust-lang.org/rustc/profile-gu...

Combining both can go pretty far in optimizing performance.