Issue #19875 has been updated by Freaky (Thomas Hurst). I've updated [fast-bytecount](https://github.com/Freaky/fast-bytecount) with autotools support, which detects the needed compiler features and exposes flags to disable bits of it. Perhaps there are other places in MRI that would benefit from some of this, which would help amortize the cost somewhat. ---------------------------------------- Bug #19875: Ruby 3.0 -> 3.1 Performance regression in String#count https://bugs.ruby-lang.org/issues/19875#change-104769 * Author: iz (Illia Zub) * Status: Open * Priority: Normal * ruby -v: 3.2.2 * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- `String#count` became slower since Ruby 3.1. Originally found by `@Freaky`: https://github.com/ruby/ruby/pull/4001#issuecomment-1714779781 Compared using the [`benchmark-driver` gem](https://github.com/benchmark-driver/benchmark-driver). ``` $ benchmark-driver tmp/string_count_benchmark_driver.yml --rbenv '3.1.1;3.1.4;2.7.2;3.2.2;3.0.6' Calculating ------------------------------------- 3.1.1 3.1.4 2.7.2 3.2.2 3.0.6 count 465.804 463.741 865.783 462.711 857.395 i/s - 10.000k times in 21.468251s 21.563768s 11.550239s 21.611783s 11.663235s Comparison: count 2.7.2: 865.8 i/s 3.0.6: 857.4 i/s - 1.01x slower 3.1.1: 465.8 i/s - 1.86x slower 3.1.4: 463.7 i/s - 1.87x slower 3.2.2: 462.7 i/s - 1.87x slower ``` Benchmark: ```yml $ cat ./tmp/string_count_benchmark_driver.yml loop_count: 10_000 prelude: | html = "\nruby\n" * 1024 * 1024 benchmark: count: html.count($/) ``` --- *Initially, I noticed the difference between `str.count($/)` and `str.lines.size` when working on the performance improvement: https://serpapi.com/blog/lines-count-failed-deployments/* ---Files-------------------------------- rb_str_len.fast (31.9 KB) rb_str_len.slow (34 KB) revert-4001.patch (1.71 KB) rb_str_count.S (11.8 KB) bytecount.c (7.23 KB) -- https://bugs.ruby-lang.org/