[luke-gruber]

This is intended to be used with the ractor-harness with --ractor-gc to see per-iteration accumulation of ractor GC data.

[thomasklemm]

Heads-up in case it's useful: gc_balloon fails on Ruby 4.0 and TruffleRuby with GC.start: unknown keyword: :global; only Ruby master accepts that keyword. Also, main renamed the harnesses after this branch was created (a1c61f6, bcee592), so on main default_harness: harness-gc and ../harness/loader now raise LoadError. The change below checks for the keyword the way harness/ractor.rb does. With it, gc_balloon runs with the gc and ractor harnesses on 4.0.9 and master, and on master with YJIT and ZJIT. Fork CI: https://github.com/thomasklemm/ruby-bench/actions/runs/42081299470

--- a/benchmarks.yml
-  default_harness: harness-gc
+  default_harness: gc
--- a/benchmarks/gc_balloon.rb
-require_relative '../harness/loader'
+require_relative '../lib/harness/loader'
@@
-  LOCAL_MAJOR_ONLY = true
+  LOCAL_MAJOR_ONLY = GC.method(:start).parameters.include?([:key, :global])

With #569 and #570, the gc harness on master also shows gc_balloon's marking time per minor and per major GC (about 9.2 ms and 1.6 ms here; the majors are the four GC.start(global: false) calls per iteration).