Issue #21032 has been updated by byroot (Jean Boussier). I dug more into this today, based on @nobu's review. `autoload?` isn't the only thing slowed down in such case. Perhaps we should try to emit a performance warning when a relative path or non-string object is appended to `$LOAD_PATH`. That would at least make it easier to notice this issue. The problem of course is that `$LOAD_PATH` is just a regular array, so there isn't a clean hook where to check for this. ---------------------------------------- Bug #21032: `Module#autoload?` is slow when `$LOAD_PATH` contains a relative path https://bugs.ruby-lang.org/issues/21032#change-111484 * Author: byroot (Jean Boussier) * Status: Open * Backport: 3.1: WONTFIX, 3.2: REQUIRED, 3.3: REQUIRED, 3.4: REQUIRED ---------------------------------------- Reproduction script: ```ruby require 'benchmark' $LOAD_PATH << 'relative-path' autoload :FOO, '/tmp/foo.rb' puts Benchmark.realtime { 500_000.times do Object.autoload?(:FOO) end } ``` The above takes 2.5 to 3 seconds on my machine, but just removing `$LOAD_PATH << 'relative-path'` make it complete in 50ms. It's such a stark difference that I think it is a bug, and it cause Zeitwerk, a very popular gem, to be way slower than it should when the load path contains relative paths. I have a patch for it, that passes all tests, but I'd appreciate some eyes on it: https://github.com/ruby/ruby/pull/12562 cc @fxn -- https://bugs.ruby-lang.org/