From: "k0kubun (Takashi Kokubun) via ruby-core" <ruby-core@...>
Date: 2026-09-14T20:16:51+00:00
Subject: [ruby-core:126711] [Ruby Bug#22220] Performance regression when requiring `aws-sdk-ec2` in Ruby 4.0.6

Issue #22220 has been updated by k0kubun (Takashi Kokubun).

Backport changed from 3.3: DONTNEED, 3.4: DONTNEED, 4.0: REQUIRED to 3.3: DONTNEED, 3.4: DONTNEED, 4.0: DONE

ruby_4_0 commit:faa5caf1b734f371ce0ea0b1ae544b47d865e551.

----------------------------------------
Bug #22220: Performance regression when requiring `aws-sdk-ec2` in Ruby 4.0.6
https://bugs.ruby-lang.org/issues/22220#change-119009

* Author: emanuelevans (Emanuel Evans)
* Status: Closed
* ruby -v: 4.0.6
* Backport: 3.3: DONTNEED, 3.4: DONTNEED, 4.0: DONE
----------------------------------------
Ruby 4.0.6 introduced a large performance regression when loading `aws-sdk-ec2` (~30s on my machine, compared to <1s for ruby 4.0.5). Script to reproduce:

```
for v in 4.0.5 4.0.6; do
  docker run --rm ruby:$v-slim bash -c '
    gem install --no-document aws-sdk-ec2 -v 1.402.0 >/dev/null 2>&1
    ruby -e "t = Process.clock_gettime(Process::CLOCK_MONOTONIC)
             require \"aws-sdk-ec2\"
             printf(\"ruby %s: %.2fs\n\", RUBY_VERSION, Process.clock_gettime(Process::CLOCK_MONOTONIC) - t)"'
done
```

It appears to be related to `Shape.new` and/or `Class.new` compile times; minimal reproduction:

```
for v in 4.0.5 4.0.6; do
  docker run --rm ruby:$v-slim ruby -e '
    src = "class Shape\n  def self.new(**) = nil\nend\nmodule M\n" +
          (1..16_000).map { |i| %(  K_#{i} = Shape.new(name: "k#{i}")) }.join("\n") + "\nend\n"
    File.write("/tmp/bench.rb", src)
    t = Process.clock_gettime(Process::CLOCK_MONOTONIC)
    RubyVM::InstructionSequence.compile_file("/tmp/bench.rb")
    printf("ruby %s: %.2fs\n", RUBY_VERSION, Process.clock_gettime(Process::CLOCK_MONOTONIC) - t)'
done
```



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