Issue #21856 has been updated by byroot (Jean Boussier). I reduced the benchmark to: ```ruby # frozen_string_literal: true require "bundler/inline" gemfile do source 'https://rubygems.org' gem "benchmark-ips" end Benchmark.ips do |x| x.report("singleton") do Object.new.singleton_class end end ``` `3.4.7`: ``` ruby 3.4.7 (2025-10-08 revision 7a5688e2a2) +PRISM [arm64-darwin25] Warming up -------------------------------------- singleton 742.338k i/100ms Calculating ------------------------------------- singleton 7.381M (± 2.2%) i/s (135.48 ns/i) - 37.117M in 5.031106s ``` `4.0.0` ``` ruby 4.0.0 (2025-12-25 revision 553f1675f3) +PRISM [arm64-darwin25] Warming up -------------------------------------- singleton 13.919k i/100ms Calculating ------------------------------------- singleton 146.202k (±28.4%) i/s (6.84 μs/i) - 668.112k in 5.059563s ``` So that's a pretty massive regression in class sweeping. I'll see what I can do. ---------------------------------------- Bug #21856: Nokogiri performance degradation since Ruby 4.0 https://bugs.ruby-lang.org/issues/21856#change-116252 * Author: ahorek (Pavel Rosický) * Status: Open * ruby -v: ruby 4.1.0dev (2026-01-31T09:41:30Z master 7ef8c470d2) +PRISM [x86_64-linux] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- Loofah sanitization is noticeably slower ``` Ruby: 3.4.8 Loofah: 2.25.0 Nokogiri: 1.19.0 Iterations: 100000 user system total real Loofah.fragment + scrub!(:prune) 26.091872 0.000000 26.091872 ( 25.110925) Loofah.scrub_fragment(:prune) 25.913185 0.010392 25.923577 ( 24.948464) Nokogiri HTML parse only 3.852690 0.000000 3.852690 ( 3.705930) Ruby: 4.0.0 & 4.0.1 Loofah: 2.25.0 Nokogiri: 1.19.0 Iterations: 100000 user system total real Loofah.fragment + scrub!(:prune) 38.094207 0.041753 38.135960 ( 36.669463) Loofah.scrub_fragment(:prune) 40.168795 0.000045 40.168840 ( 38.561806) Nokogiri HTML parse only 4.012936 0.052024 4.064960 ( 3.913272) Ruby: 4.1.0 (ruby 4.1.0dev (2026-01-31T09:41:30Z master 7ef8c470d2) +PRISM [x86_64-linux]) Loofah: 2.25.0 Nokogiri: 1.19.0 Iterations: 100000 user system total real Loofah.fragment + scrub!(:prune) 39.004228 0.000000 39.004228 ( 37.694873) Loofah.scrub_fragment(:prune) 39.043199 0.031284 39.074483 ( 37.182785) Nokogiri HTML parse only 3.889100 0.010427 3.899527 ( 3.741622) ``` Originally reported https://www.redmine.org/issues/43737 ---Files-------------------------------- benchmark.rb (1002 Bytes) -- https://bugs.ruby-lang.org/