[ruby-core:115995] [Ruby master Bug#20112] Ractors not working properly in ruby 3.3.0

3 Jan 2024

      Issue #20112 has been reported by ariasdiniz (Aria Diniz).

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Bug #20112: Ractors not working properly in ruby 3.3.0
https://bugs.ruby-lang.org/issues/20112

* Author: ariasdiniz (Aria Diniz)
* Status: Open
* Priority: Normal
* ruby -v: 3.3.0
* Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN
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I recently installed Ruby 3.3.0, and noticed that some of my scripts that use Ractors started to struggle with performance. After doing some benchmarks, I noticed that, while Ractors seem to be working well on Ruby 3.2.2, they're not working properly on 3.3.0.

I'm using Ubuntu 22.04.3 LTS

Here is the benchmark code:

``` ruby
# frozen_string_literal: true

require 'benchmark'

Ractor.new { :warmup } if defined?(Ractor)

Benchmark.bmbm do |x|
  x.report("Thread: ") do
    threads = []
    8.times do |i|
      threads << Thread.new do
        20000000.times do |j|
          ((i * 20000000) + j)**2
        end
      end
    end
    threads.each(&:join)
  end
  x.report("Ractor: ") do
    ractors = []
    0..8.times do |i|
      ractors << Ractor.new(i) do |k|
        20000000.times do |j|
          ((k * 20000000) + j)**2
        end
      end
    end
    ractors.map(&:take)
  end
end

```

Here is the results for Ruby 3.2.2:

Rehearsal --------------------------------------------
Thread:    7.666909   0.001091   7.668000 (  7.675266)
Ractor:   19.318528   0.012017  19.330545 (  2.505888)
---------------------------------- total: 26.998545sec

               user     system      total        real
Thread:    7.918141   0.004011   7.922152 (  7.928772)
Ractor:   19.366414   0.003954  19.370368 (  2.517993)

Here is the results for Ruby 3.3.0:

Rehearsal --------------------------------------------
Thread:    8.634152   0.010895   8.645047 (  8.645104)
Ractor:  100.172179   0.035985 100.208164 ( 15.213245)
--------------------------------- total: 108.853211sec

               user     system      total        real
Thread:    9.451236   0.004002   9.455238 (  9.460132)
Ractor:  118.463294   0.119942 118.583236 ( 18.462157)

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