Brew: `brew --prefix <package>` is much slower than `brew --prefix`

[rotu]

• [X] ran brew update and can still reproduce the problem?
• [X] ran brew doctor, fixed all issues and can still reproduce the problem?
• [X] ran brew config and brew doctor and included their output with your issue?

What you were trying to do (and why)

Edit my .zshrc to use a brew-installed package

What happened (include command output)

My .zshrc ran very slowly. It appears brew --prefix <package> takes almost a second,

time brew --prefix openssl
/usr/local/opt/[email protected]
brew --prefix openssl  0.76s user 0.54s system 92% cpu 1.412 total

time brew --prefix bzip2
/usr/local/opt/bzip2
brew --prefix bzip2  0.73s user 0.47s system 92% cpu 1.288 total

time brew --prefix autoconf
/usr/local/opt/autoconf
brew --prefix autoconf  0.79s user 0.55s system 90% cpu 1.483 total

## What you expected to happen I expect `brew --prefix ` to run about as fast as `brew --prefix`, which takes 0.02 seconds.

$ time brew --prefix
/usr/local
brew --prefix  0.02s user 0.03s system 77% cpu 0.062 total

## Step-by-step reproduction instructions (by running `brew` commands)

brew install openssl
time brew --prefix openssl

## Output of `brew config` and `brew doctor` commands NB: although this is on a beta MacOS version, I strongly suspect the issue is not limited to it.

HOMEBREW_VERSION: 2.4.9-164-gdf16e9f
ORIGIN: https://github.com/Homebrew/brew
HEAD: df16e9f2de5df897f2a4ae95b1a40edc54dfc1b8
Last commit: 8 hours ago
Core tap ORIGIN: https://github.com/Homebrew/homebrew-core
Core tap HEAD: 16a20d5f3c9a9868f61f312b62c2cb6e1f27c53a
Core tap last commit: 29 minutes ago
HOMEBREW_PREFIX: /usr/local
HOMEBREW_EDITOR: subl -w
HOMEBREW_MAKE_JOBS: 4
CPU: quad-core 64-bit haswell
Homebrew Ruby: 2.6.3 => /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/bin/ruby
Clang: 12.0 build 1200
Git: 2.24.3 => /Library/Developer/CommandLineTools/usr/bin/git
Curl: 7.64.1 => /usr/bin/curl
Java: 14.0.2
macOS: 11.0-x86_64
CLT: 12.0.0.0.1.1595091463
Xcode: N/A

Please note that these warnings are just used to help the Homebrew maintainers

with debugging if you file an issue. If everything you use Homebrew for is

working fine: please don't worry or file an issue; just ignore this. Thanks!


Warning: You are using macOS 11.0.

We do not provide support for this pre-release version.

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Please create pull requests instead of asking for help on Homebrew's GitHub,

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[jonchang]

We'd accept a pull request to improve the speed, but no maintainers are working on this currently. See brew prof to use the Ruby profiler to see where things are slow.

[claui]

I’ve given up on trying to fix this. In my personal shell profile, I now eval "$(brew shellenv)", and I’ve replaced all invocations of brew --prefix _FORMULA_ with:

"${HOMEBREW_PREFIX:-$(brew --prefix)}/opt/nvm"

[rotu]

@jonchang Seems like brew prof is functionally broken:

$ brew prof --prefix openssl
Usage: brew prof command

Run Homebrew with the Ruby profiler, e.g. brew prof readall.

    -q, --quiet                      Suppress any warnings.
    -v, --verbose                    Make some output more verbose.
    -d, --debug                      Display any debugging information.
    -h, --help                       Show this message.
Error: invalid option: --prefix

[Bo98]

Opened #8192 to fix that.

[rotu]

Thanks, @Bo98. Using your code I was able to make some traces. But the data doesn't tell me much, largely because I have no idea what I'm doing in Ruby. prof.zip

Strangely, running this with prof closes the absolute time difference between --prefix and --prefix <pkg>. I think that some heavy modules are being instantiated with brew --prefix <pkg>, and the interpreter causes this to be cached.

Whatever it is, the stack profile just looks like a tower of Kernel#require followed by a tiiiiny bit of application code.

➜  ~ time brew --prefix
/usr/local
brew --prefix  0.01s user 0.02s system 78% cpu 0.050 total
➜  ~ time brew --prefix openssl
/usr/local/opt/[email protected]
brew --prefix openssl  0.87s user 0.52s system 92% cpu 1.499 total

➜  ~ time brew prof --prefix        
/usr/local
brew prof --prefix  3.44s user 1.13s system 97% cpu 4.687 total
➜  ~ time brew prof --prefix openssl
/usr/local/opt/[email protected]
brew prof --prefix openssl  3.75s user 1.24s system 97% cpu 5.112 total

[jonchang]

brew --prefix <formula> needs Ruby, but brew --prefix has a bash shortcut with a Ruby fallback. brew prof calls the Ruby version in both cases.

[rotu]

Thank, @jonchang! That makes a lot of sense. So I guess this would be huge project to make performant :-(

[MikeMcQuaid]

So I guess this would be huge project to make performant :-(

Yes. The issue is Homebrew's "boot time" due to gem usage e.g. ActiveSupport.