prelude: |
  long_lived = []

  if RUBY_VERSION > "2.2.0"
    3.times{ GC.start(full_mark: false, immediate_mark: true, immediate_sweep: true) }
  elsif
    GC.start
  end

  short_lived = ''

benchmark:
  vm_gc_wb_ary_promoted: |
    long_lived[0] = short_lived # write barrier
loop_count: 30000000