Enable Link-Time Optimization (LTO)

[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.

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 dist or release-lto profile where additionally to regular release optimizations LTO will also 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 should also help to reduce the build-time overhead with LTO. If we enable it on the Cargo profile level, users, who install the application with cargo install, will get the LTO-optimized version "automatically". E.g., check cargo-outdated Release profile.

Basically, it can be enabled with the following lines:

[profile.release]
lto = true

Thank you.

[icepuma]

https://github.com/johnthagen/min-sized-rust is also a good source on how to do this :)

[zamazan4ik]

Yeah! I also can recommend a handy Cargo extension - https://github.com/Kobzol/cargo-wizard

[bomgar]

I had to deactivate it here explicitly. If I enable it there it breaks the build.

I did not investigate this further. But I don't want to enable it if I don't understand why this breaks.

[bomgar]

The log is longer than that but a lot of those:

  = note: /usr/bin/ld: fblog-aur/src/fblog-4.13.0/target/release/deps/fblog-50db4c743190de0e.fblog.e5a3c9bd97f2765e-cgu.02.rcgu.o: in function `mlua::function::Function::call':
          fblog.e5a3c9bd97f2765e-cgu.02:(.text._ZN4mlua8function8Function4call17h23ab9af08fb82300E+0x23): undefined reference to `lua_gettop'
          /usr/bin/ld: fblog.e5a3c9bd97f2765e-cgu.02:(.text._ZN4mlua8function8Function4call17h23ab9af08fb82300E+0x39): undefined reference to `lua_checkstack'
          /usr/bin/ld: fblog.e5a3c9bd97f2765e-cgu.02:(.text._ZN4mlua8function8Function4call17h23ab9af08fb82300E+0x54): undefined reference to `lua_pushcclosure'
          /usr/bin/ld: fblog.e5a3c9bd97f2765e-cgu.02:(.text._ZN4mlua8function8Function4call17h23ab9af08fb82300E+0x5d): undefined reference to `lua_gettop'
          /usr/bin/ld: fblog.e5a3c9bd97f2765e-cgu.02:(.text._ZN4mlua8function8Function4call17h23ab9af08fb82300E+0x83): undefined reference to `lua_pcallk'
          /usr/bin/ld: fblog.e5a3c9bd97f2765e-cgu.02:(.text._ZN4mlua8function8Function4call17h23ab9af08fb82300E+0xd3): undefined reference to `lua_gettop'
          /usr/bin/ld: fblog.e5a3c9bd97f2765e-cgu.02:(.text._ZN4mlua8function8Function4call17h23ab9af08fb82300E+0xea): undefined reference to `lua_toboolean'

[zamazan4ik]

Does it come from lto = true (aka Fat LTO)? Did you try to use lto = "thin" (aka Thin LTO) instead?

Seems like one of the project's dependencies is surprisingly not okay with enabling LTO.

[bomgar]

I did not modify the Cargo.toml. It seems to be enabled by default with pkgbuild

[zamazan4ik]

What kind of LTO is enabled by pkgbuild by default in Arch? Is it possible to override this setting if we want for example use Thin LTO instead of Fat?

[bomgar]

I don't know. I did not have the time to investigate further.