void PSParallelCompact::compact() {

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

      EventMark m("5 compact");
      // trace("5");
      TraceTime tm("compaction phase", print_phases(), true, gclog_or_tty);

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

      ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
      assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
      PSOldGen* old_gen = heap->old_gen();
      old_gen->start_array()->reset();
      uint parallel_gc_threads = heap->gc_task_manager()->workers();
      TaskQueueSetSuper* qset = ParCompactionManager::region_array();
      ParallelTaskTerminator terminator(parallel_gc_threads, qset);

  {- -------------------------------------------
  (1) GCTaskQueue::create() で GCTaskQueue を作り, 
      そこに DrainStacksCompactionTask, UpdateDensePrefixTask, および 
      StealRegionCompactionTask をつめる.

      (See: PSParallelCompact::enqueue_region_draining_tasks(), 
            PSParallelCompact::enqueue_dense_prefix_tasks(), 
            PSParallelCompact::enqueue_region_stealing_tasks())
      ---------------------------------------- -}

      GCTaskQueue* q = GCTaskQueue::create();
      enqueue_region_draining_tasks(q, parallel_gc_threads);
      enqueue_dense_prefix_tasks(q, parallel_gc_threads);
      enqueue_region_stealing_tasks(q, &terminator, parallel_gc_threads);

      {

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

        TraceTime tm_pc("par compact", print_phases(), true, gclog_or_tty);

  {- -------------------------------------------
  (1) 最後に, 以上の処理が終了するまで待機するための WaitForBarrierGCTask も追加しておく.
      ---------------------------------------- -}

        WaitForBarrierGCTask* fin = WaitForBarrierGCTask::create();
        q->enqueue(fin);

  {- -------------------------------------------
  (1) GCTaskManager::add_list() で, GCTask をキューに追加して GCTaskThread 達に実行させる.
      ---------------------------------------- -}

        gc_task_manager()->add_list(q);

  {- -------------------------------------------
  (1) WaitForBarrierGCTask::wait_for() で GCTask が全て実行されるまで待機する.
      待機が解けたら, WaitForBarrierGCTask::destroy() で WaitForBarrierGCTask オブジェクトを破棄する.
      ---------------------------------------- -}

        fin->wait_for();

        // We have to release the barrier tasks!
        WaitForBarrierGCTask::destroy(fin);

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

    #ifdef  ASSERT
        // Verify that all regions have been processed before the deferred updates.
        // Note that perm_space_id is skipped; this type of verification is not
        // valid until the perm gen is compacted by regions.
        for (unsigned int id = old_space_id; id < last_space_id; ++id) {
          verify_complete(SpaceId(id));
        }
    #endif
      }

  {- -------------------------------------------
  (1) PSParallelCompact::update_deferred_objects() を呼んで, 
      複数 region にまたがっていたために
      ポインタの修正が行えていないオブジェクトに対して処理を行う.
      (なお, ここで使用する ParCompactionManager は何でもいいので, 適当に 0 番のものを使っている)
      ---------------------------------------- -}

      {
        // Update the deferred objects, if any.  Any compaction manager can be used.
        TraceTime tm_du("deferred updates", print_phases(), true, gclog_or_tty);
        ParCompactionManager* cm = ParCompactionManager::manager_array(0);
        for (unsigned int id = old_space_id; id < last_space_id; ++id) {
          update_deferred_objects(cm, SpaceId(id));
        }
      }
    }