Evaluate using more optimizations like LTO and PGO

[zamazan4ik]

Hi!

I noticed that 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 performance a bit (in this case, it's not critical at all but anyway).

I suggest enabling 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. If you think that a regular Release build should not be affected by such a change as well, then I suggest adding an additional release-lto profile where additionally to regular release optimizations LTO also will be added. Such a change simplifies life for maintainers and others interested in the project persons who want to build the most performant version of the application. Using ThinLTO also should help).

Additionally to LTO, I can suggest evaluating for Possum more advanced optimizations like Profile-Guided Optimization (PGO) and Post-Link Optimization (PLO). I have a lot of information (including a lot of benchmarks!) in my repository: https://github.com/zamazan4ik/awesome-pgo . However, right now LTO and PGO cannot be enabled at the same time due to a bug in Rustc: rust-lang/rust#115344 (comment) . So for now I suggest just enabling LTO and waiting for the fix in the Rustc's upstream.

Thank you.

P.S. I created the Issue since Discussions are disabled for the repository. It's not a bug report - just an improvement idea.

[anacrolix]

Thank you kindly! The LTO optimization would make sense, the library is used in embedded cases where it's likely that reducing its space footprint is positive. I'm not sure that in general the library is CPU sensitive, but it all helps.

[anacrolix]

I opened discussions, thanks.

[anacrolix]

I tried with

[profile.release]
lto = "fat"
opt-level = "s"

And got some milld size improvements. I didn't check any benchmarks.