[ruby-core:112618] [Ruby master Bug#18572] Performance regression when invoking refined methods

27 Feb 2023

      Issue #18572 has been updated by Eregon (Benoit Daloze).

Potential fix: https://github.com/ruby/ruby/pull/4323

----------------------------------------
Bug #18572: Performance regression when invoking refined methods
https://bugs.ruby-lang.org/issues/18572#change-102065

* Author: palkan (Vladimir Dementyev)
* Status: Assigned
* Priority: Normal
* Assignee: ko1 (Koichi Sasada)
* Backport: 2.6: UNKNOWN, 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
Since Ruby 3.0, defining a refinement for a method slows down its execution even if we do not activate the refinement:

```ruby
require "benchmark_driver"

source = <<~RUBY
class Hash
  def symbolize_keys
    transform_keys { |key| key.to_sym rescue key }
  end
  def refined_symbolize_keys
    transform_keys { |key| key.to_sym rescue key }
  end
end
module HashRefinements
  refine Hash do
    def refined_symbolize_keys
      raise "never called"
    end
  end
end
HASH = {foo: 1, bar: 2, baz: 3}
class Foo
  def original
  end
  def refined
  end
end
module FooRefinements
  refine Foo do
    def refined
      raise "never called"
    end
  end
end
FOO = Foo.new
RUBY

Benchmark.driver do |x|
  x.prelude %Q{
    #{source}
  }
  x.report "#symbolize_keys original", %{ HASH.symbolize_keys }
  x.report "#symbolize_keys refined", %{ HASH.refined_symbolize_keys }
end

Benchmark.driver do |x|
  x.prelude %Q{
    #{source}
  }
  x.report "no-op original", %{ FOO.original }
  x.report "no-op refined", %{ FOO.refined }
end
```

The results for Ruby 3.1:

```sh
...

Comparison:
#symbolize_keys original:   2372420.1 i/s 
 #symbolize_keys refined:   1941019.0 i/s - 1.22x  slower

...

Comparison:
      no-op original:  51790974.2 i/s 
       no-op refined:  14456518.9 i/s - 3.58x  slower
```

For Ruby 2.6 and 2.7:

```sh
Comparison:
#symbolize_keys original:   2278339.7 i/s 
 #symbolize_keys refined:   2264153.1 i/s - 1.01x  slower

...

Comparison:
       no-op refined:  64178338.5 i/s 
      no-op original:  63357980.1 i/s - 1.01x  slower
```

You can find the full code and more results in this [gist](https://gist.github.com/palkan/637dc83edd86d70b5dbf72f2a4d702e5).

P.S.  The problem was originally noticed by @byroot, see https://github.com/ruby-i18n/i18n/pull/573

-- 
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