void work(int i) {

  {- -------------------------------------------
  (1) (変数宣言など)
      ---------------------------------------- -}

        double start = os::elapsedTime();
        FreeRegionList local_cleanup_list("Local Cleanup List");
        HumongousRegionSet humongous_proxy_set("Local Cleanup Humongous Proxy Set");
        HRRSCleanupTask hrrs_cleanup_task;
        G1NoteEndOfConcMarkClosure g1_note_end(_g1h, i, &local_cleanup_list,
                                               &humongous_proxy_set,
                                               &hrrs_cleanup_task);

  {- -------------------------------------------
  (1) G1NoteEndOfConcMarkClosure を引数として
      G1CollectedHeap::heap_region_par_iterate_chunked() または G1CollectedHeap::heap_region_iterate() を呼び出し, 
      Cleanup 処理を行う.

      (G1CollectedHeap::use_parallel_gc_threads() が true であれば, 
       G1CollectedHeap::heap_region_par_iterate_chunked() を使ってマルチスレッドで処理する.
       そうでなければ, G1CollectedHeap::heap_region_iterate() によるシングルスレッド処理を行う.)
      ---------------------------------------- -}

        if (G1CollectedHeap::use_parallel_gc_threads()) {
          _g1h->heap_region_par_iterate_chunked(&g1_note_end, i,
                                                HeapRegion::NoteEndClaimValue);
        } else {
          _g1h->heap_region_iterate(&g1_note_end);
        }

  {- -------------------------------------------
  (1) (assert)
      ---------------------------------------- -}

        assert(g1_note_end.complete(), "Shouldn't have yielded!");

  {- -------------------------------------------
  (1) 
      ---------------------------------------- -}

        // Now update the lists
        _g1h->update_sets_after_freeing_regions(g1_note_end.freed_bytes(),
                                                NULL /* free_list */,
                                                &humongous_proxy_set,
                                                true /* par */);
        {
          MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
          _max_live_bytes += g1_note_end.max_live_bytes();
          _freed_bytes += g1_note_end.freed_bytes();

          _cleanup_list->add_as_tail(&local_cleanup_list);
          assert(local_cleanup_list.is_empty(), "post-condition");

          HeapRegionRemSet::finish_cleanup_task(&hrrs_cleanup_task);
        }

  {- -------------------------------------------
  (1) (トレース出力)
      ---------------------------------------- -}

        double end = os::elapsedTime();
        if (G1PrintParCleanupStats) {
          gclog_or_tty->print("     Worker thread %d [%8.3f..%8.3f = %8.3f ms] "
                              "claimed %d regions (tot = %8.3f ms, max = %8.3f ms).\n",
                              i, start, end, (end-start)*1000.0,
                              g1_note_end.regions_claimed(),
                              g1_note_end.claimed_region_time_sec()*1000.0,
                              g1_note_end.max_region_time_sec()*1000.0);
        }
      }