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September 2024

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[ruby-core:118637] [Ruby master Bug#20641] `lib/bundled_gems.rb` makes `Kernel.require` over 100x slower
by byroot (Jean Boussier) 02 Sep '24

02 Sep '24

Issue #20641 has been reported by byroot (Jean Boussier). ---------------------------------------- Bug #20641: `lib/bundled_gems.rb` makes `Kernel.require` over 100x slower https://bugs.ruby-lang.org/issues/20641 * Author: byroot (Jean Boussier) * Status: Open * Backport: 3.1: DONTNEED, 3.2: DONTNEED, 3.3: REQUIRED ---------------------------------------- I just discovered this while profiling Active Record's test suite, and I noticed 40% of the runtime was in `$LOAD_PATH.resolve_feature_path`, so much I thought it was a profiler bug. But it turns out it's real. Various APIs do call `require` late, for instance Psych calls `require 'date'` every single time it parses a date: https://github.com/ruby/psych/blob/be0ba74e5613c20f213403e15914d24944c2652d… I've put together a quick benchmark: ```ruby # frozen_string_literal: true require "bundler/inline" gemfile(true) do source "https://rubygems.org" gem "benchmark-ips" end Benchmark.ips do |x| x.report(RUBY_VERSION) { require "erb" } x.save! "/tmp/require.bench" x.compare! end ``` And the difference is massive: ``` Calculating ------------------------------------- 3.2.2 6.450M (± 1.2%) i/s - 32.822M in 5.089538s Comparison: 3.2.2: 6449899.4 i/s 3.3.3: 46996.8 i/s - 137.24x slower ``` And that's with a small `$LOAD_PATH`, the bigger the application, the worse it is, if I add: ```ruby 100.times do |i| $LOAD_PATH.unshift("/tmp/empty-#{i}") end ``` ``` Calculating ------------------------------------- 3.3.3 6.198k (± 6.1%) i/s - 30.968k in 5.018955s Comparison: 3.2.2: 3380939.6 i/s 3.3.3: 6198.4 i/s - 545.46x slower ``` I'm looking at a way to speed this up, but this is big enough that I believe we should backport the fix. cc @hsbt -- https://bugs.ruby-lang.org/

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