global: tweak active_support requires.

[MikeMcQuaid]

I was hoping that these would speed up boot but unfortunately they make no difference. They are a bit more minimal anyway so probably a good idea.

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[Bo98]

I was hoping that these would speed up boot but unfortunately they make no difference

The problem I suspect is because require is not exactly the quickest thing in the world.

The load path in brew is quite large, and that is what require searches every time. It doesn't just check for a file's existance in a directory and move on however - it does other things like resolving symlinks etc so it's not the cheapest operation.

I wonder how much quicker things would be if we (for other requiring brew files - not gems) used either require_relative or require with an absolute path (can be a helper function). Ruby sort of nudges you this way anyway - brew files wouldn't ordinarily be in the load path but we make it so.

[MikeMcQuaid]

The load path in brew is quite large, and that is what require searches every time. It doesn't just check for a file's existance in a directory and move on however - it does other things like resolving symlinks etc so it's not the cheapest operation.

Yeh, I was thinking that too. Perhaps if we turned these all into require with a path or require_relative then things could be faster (as you've mentioned).

Another option is extracting the actual logic we care about and vendoring that.

[Bo98]

Played around with the require stuff. It is quicker to give an absolute path but the total savings were only about 75ms. If I can read prof properly (I probably can't) I think the changes I did covered about one quarter of the total require calls.

I didn't touch any taps however.

[MikeMcQuaid]

Yeh, that doesn't sound like much. My guess is it may be the actual code that ActiveSupport is running rather than purely the require lookups.

[Bo98]

There's other micro-optimisations like only requiring debrew/irb when it's actually needed (it takes 30ms to load on its own). It's just a case of seeing what is worth it because it'll be a combination of things rather than one specific cause.

[Bo98]

require "formula" is also a good target that I've played around with. I drafted changes to avoid that requiring file unless needed and saw as much as 150ms improvements.

Cask commands are some of the biggest culprits of requiring half of Homebrew (I profiled cask/cmd.rb as the slowest file to load in Homebrew). They're not lazily loaded like regular brew commands, probably purely because of the brew cask output that lists all subcommands. Subcommands in taps are lazily loaded.

[MikeMcQuaid]

I think active_support is the elephant in the room here; I'm not sure it's worth dealing with other things before that.

[Bo98]

Reducing the requires to just active_support/core_ext/object/blank and active_support/core_ext/object/try saves about 70ms.