Ref: https://github.com/ruby/json/issues/655 Followup: https://github.com/ruby/json/issues/657 Assuming the generator might be used for fairly small documents we can start with a reasonable buffer size of the stack, and if we outgrow it, we can spill on the heap. In a way this is optimizing for micro-benchmarks, but there are valid use case for fiarly small JSON document in actual real world scenarios, so trashing the GC less in such case make sense. Before: ``` ruby 3.3.4 (2024-07-09 revision https://github.com/ruby/json/commit/be1089c8ec) +YJIT [arm64-darwin23] Warming up -------------------------------------- Oj 518.700k i/100ms JSON reuse 483.370k i/100ms Calculating ------------------------------------- Oj 5.722M (± 1.8%) i/s (174.76 ns/i) - 29.047M in 5.077823s JSON reuse 5.278M (± 1.5%) i/s (189.46 ns/i) - 26.585M in 5.038172s Comparison: Oj: 5722283.8 i/s JSON reuse: 5278061.7 i/s - 1.08x slower ``` After: ``` ruby 3.3.4 (2024-07-09 revision https://github.com/ruby/json/commit/be1089c8ec) +YJIT [arm64-darwin23] Warming up -------------------------------------- Oj 517.837k i/100ms JSON reuse 548.871k i/100ms Calculating ------------------------------------- Oj 5.693M (± 1.6%) i/s (175.65 ns/i) - 28.481M in 5.004056s JSON reuse 5.855M (± 1.2%) i/s (170.80 ns/i) - 29.639M in 5.063004s Comparison: Oj: 5692985.6 i/s JSON reuse: 5854857.9 i/s - 1.03x faster ``` https://github.com/ruby/json/commit/fe607f4806