[ruby-core:115252] [Ruby master Bug#19989] Fix refinement refine performance

5 Nov 2023

      Issue #19989 has been updated by ahorek (Pavel Rosický).
...
By fixing this, we could improve refinement performance and encourage more adoption since refinements are a powerful way to make small adjustments to the language without resorting to more complicated solutions -- or worse -- using monkey patches.
this shouldn't really affect the runtime performance of real programs unless you're dynamically creating refined modules like in your benchmark (which is also slow). Do you have an example where this could be a problem?

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Bug #19989: Fix refinement refine performance
https://bugs.ruby-lang.org/issues/19989#change-105163

* Author: bkuhlmann (Brooke Kuhlmann)
* Status: Open
* Priority: Normal
* ruby -v: ruby 3.2.2 (2023-03-30 revision e51014f9c0) +YJIT [arm64-darwin22.4.0]
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN
----------------------------------------
## Why

Hello. 👋 Would it be possible to improve the performance of refining an object as I'm seeing a significant performance cost? I know some of this is already known but, when searching through existing issues, I couldn't find any issue that specifically mentioned or called attention to `refine` performance.

My C skills are not that great but it seems that `rb_mod_refine` ([source](https://github.com/ruby/ruby/blob/master/eval.c#L1412-L1459)) might be the primary source of complexity and performance degradation?

By fixing this, we could improve refinement performance and encourage more adoption since refinements are a powerful way to make small adjustments to the language without resorting to more complicated solutions -- or worse -- using monkey patches.

## How

Here's the benchmark I'm using:

``` 
#! /usr/bin/env ruby
# frozen_string_literal: true

require "bundler/inline"

gemfile true do
  source "https://rubygems.org"

  gem "benchmark-ips"
end

Benchmark.ips do |benchmark|
  benchmark.config time: 5, warmup: 2

  benchmark.report "With" do
    Module.new do
      refine String do
        def dud = true
      end
    end
  end

  benchmark.report "Without" do
    Module.new do
      def dud = true
    end
  end

  benchmark.compare!
end
```

When running the above, I'm getting the following results (this is a random sample):

**Ruby 2.6.6** (ruby 2.6.6p146 (2020-03-31 revision 67876) [-darwin22])

*ℹ️ Temporarily refactored the benchmark to not use endless methods for this version.*

``` 
Warming up --------------------------------------
                With   745.000  i/100ms
             Without    67.593k i/100ms
Calculating -------------------------------------
                With     10.849k (±168.6%) i/s -     18.625k in   5.359230s
             Without    680.199k (± 5.8%) i/s -      3.447M in   5.085558s

Comparison:
             Without:   680198.8 i/s
                With:    10849.1 i/s - 62.70x  slower
```

**Ruby 3.2.2** (ruby 3.2.2 (2023-03-30 revision e51014f9c0) +YJIT [arm64-darwin22.4.0])

``` 
Warming up --------------------------------------
                With   959.000  i/100ms
             Without   297.091k i/100ms
Calculating -------------------------------------
                With     21.856k (±198.5%) i/s -     30.688k in   5.509103s
             Without      3.281M (± 5.8%) i/s -     16.637M in   5.082246s

Comparison:
             Without:  3281310.6 i/s
                With:    21856.1 i/s - 150.13x  slower
```

**Ruby 3.3.3 Preview 2** (ruby 3.3.0preview2 (2023-09-14 master e50fcca9a7) +YJIT [arm64-darwin22.6.0])

``` 
Warming up --------------------------------------
                With     1.044k i/100ms
             Without   288.264k i/100ms
Calculating -------------------------------------
                With     24.044k (±192.0%) i/s -     29.232k in   5.305651s
             Without      3.096M (± 8.0%) i/s -     15.566M in   5.059470s

Comparison:
             Without:  3095640.6 i/s
                With:    24043.8 i/s - 128.75x  slower
```

## Notes

Here's the environment I'm using:

- **macOS**: 13.6.1, Apple M1

-- 
https://bugs.ruby-lang.org/