(exa PR) 1160: Update Cargo.toml to optimise binaries for size

[cafkafk]

https://github.com/ogham/exa/pulls/1160

[cafkafk]

This looks obviously correct, but opinionated. What do you think @sbatial ?

Specially codegen-units = 1 is interesting, because while it would definitely be preferred for e.g. release binaries it would add a long build time for people compiling from source. I'm not for or against, but I'm not sure what the best option is.

[sbatial]

I've ran the possible combinations and I'd say strip = true would be sufficient.

lto = true	strip = true	opt-level = "z"	codegen-units = 1	size in MB
x	x	x		1.2
x	x	x	x	1.2
x	x			1.5
x	x		x	1.5
x		x		3.3
x		x	x	3.3
x				3.6
x			x	3.6

Because I didn't know what to make of the opt-levels and the cargo documentation specifically says

It is recommended to experiment with different levels to find the right balance for your project.

I did do just that:

lto = true	strip = true	opt-level	size in MB
x	x	0	3.0
x	x	1	1.6
x	x	2	1.4
x	x	3	1.5
x	x	s	1.2
x	x	z	1.5

With the opt-levels being:

• 0: no optimizations
• 1: basic optimizations
• 2: some optimizations
• 3: all optimizations
• "s": optimize for binary size
• "z": optimize for binary size, but also turn off loop vectorization.

(once again from the cargo book section linked above)

What is vectorization? I have no clue either, but apparently it is optimizing for modern CPU architectures by/and using some level of parallelization for loops: https://en.wikipedia.org/wiki/Automatic_vectorization

So my final verdict:

• strip: ✔️
• opt-level: "s" or "z", i don't really care. Let's just go with "s" and see if there are any problems
• codegen-units = 1 ❌

[sbatial]

See previous comment

[sbatial]

🚀

[sbatial]

Forgot to mention: strip needs nightly cargo