Issue #21696 has been updated by ufuk (Ufuk Kayserilioglu). Did 3.5-preview1 have the same behaviour? If not, could you bisect between the two releases to find the commit that changed the behaviour? ---------------------------------------- Bug #21696: Performance degradation for long running processes in Ruby 4.0.0-preview2 https://bugs.ruby-lang.org/issues/21696#change-115244 * Author: easydwh (Ivo Herweijer) * Status: Open * 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) -- https://bugs.ruby-lang.org/