Issue #21696 has been updated by easydwh (Ivo Herweijer). @luke-gru FWIW 4.0.0-preview3 performs normally. ---------------------------------------- Bug #21696: Performance degradation for long running processes in Ruby 4.0.0-preview2 https://bugs.ruby-lang.org/issues/21696#change-115825 * Author: easydwh (Ivo Herweijer) * Status: Closed * ruby -v: ruby 4.0.0preview2 (2025-11-17 master 4fa6e9938c) +PRISM [x86_64-linux] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- When running my RubyMeasureResponsetime tool (https://github.com/easydatawarehousing/ruby_measure_responsetime) on Ruby 4.0.0-preview2, a slow but steady performance degradation is measurable. Both the Rails and the Roda based test applications show this. And both with and without yjit. The Rails application when using yjit also seems to have increasing memory usage over time. Running the same tests on Ruby 3.4.7 shows stable performance and memory usage. I have included some plots showing this behavior. ---Files-------------------------------- rails_devise_2_ruby-4.0.0.jpg (965 KB) rodauth_2_ruby-4.0.0 YJIT.jpg (973 KB) rodauth_2_ruby-4.0.0.jpg (1.02 MB) rails_devise_2_ruby-4.0.0 YJIT.jpg (917 KB) rails_devise_0_memory.png (31.2 KB) rodauth_0_overview.png (43.8 KB) rodauth_0_memory.png (15.6 KB) rodauth_1_ruby-3.4.7.png (152 KB) rodauth_1_ruby-3.4.7 YJIT.png (121 KB) rodauth_1_ruby-4.0.0.png (119 KB) rodauth_1_ruby-4.0.0 YJIT.png (118 KB) -- https://bugs.ruby-lang.org/