Homebrew startup performance tweaks#21734
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MikeMcQuaid merged 1 commit intomainfrom Mar 14, 2026
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Pull request overview
This PR targets improved cold startup performance for common brew invocations by deferring or hoisting work out of hot paths in the shell and Ruby entrypoints.
Changes:
- Optimize
bin/brewstartup by avoidingdirnameand by precomputing the exported-vars exclusion regex once. - Defer more expensive initialization in
brew.sh(e.g., macOS version parsing, wrapper checks, curl setup) until it’s actually needed. - Refactor
brew.rbcommand detection/dispatch to reduce work on startup and avoid repeated external command path lookups.
Reviewed changes
Copilot reviewed 2 out of 3 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
bin/brew |
Replaces dirname with parameter expansion in symlink resolution; hoists env-file exported-var regex construction. |
Library/Homebrew/brew.sh |
Defers wrapper checking and macOS version parsing; moves setup_curl and default domain initialization later. |
Library/Homebrew/brew.rb |
Refactors command parsing and external command detection to reduce startup work. |
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Move some stuff around to improve cold startup performance. `brew --prefix` went from about 16.5 ms to 9.0 ms `brew help` went from about 16.5 ms to 8.7 ms.
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p-linnane
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Mar 14, 2026
Bo98
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Mar 17, 2026
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| if [[ -n "${HOMEBREW_MACOS}" ]] | ||
| then | ||
| HOMEBREW_MACOS_VERSION="$(/usr/bin/sw_vers -productVersion)" |
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Looks like this is now set too late for shellenv:
brew/Library/Homebrew/cmd/shellenv.sh
Line 31 in aba2263
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Move some stuff around to improve cold startup performance.
brew --prefixwent from about 16.5 ms to 9.0 msbrew helpwent from about 16.5 ms to 8.7 ms.brew lgtm(style, typechecking and tests) with your changes locally?Used OpenAI Codex to test with manual testing and human review passes on both high-level approach and specific code changes.