[ruby/psych] Optimize cache with `compare_by_identity`

Using `compare_by_identity` gives a 4x performance boost on cache hits.
Benchmark in https://github.com/JuanitoFatas/fast-ruby/issues/189

1 files changed, 3 insertions, 0 deletions

diff --git a/test/psych/test_ractor.rb b/test/psych/test_ractor.rb
index 90e40360c0..2f8d5ca18d 100644
--- a/test/psych/test_ractor.rb
+++ b/test/psych/test_ractor.rb
@@ -24,6 +24,9 @@ class TestPsychRactor < Test::Unit::TestCase
   end
 
   def test_ractor_config
+    # Config is ractor-local
+    # Test is to make sure it works, even though usage is probably very low.
+    # The methods are not documented and might be deprecated one day
     assert_ractor(<<~RUBY, require_relative: 'helper')
       r = Ractor.new do
         Psych.add_builtin_type 'omap' do |type, val|