// Checkpoint the roots into this generation from outside
// this generation. [Note this initial checkpoint need only
// be approximate -- we'll do a catch up phase subsequently.]

void ConcurrentMark::checkpointRootsInitial() {

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

      assert(SafepointSynchronize::is_at_safepoint(), "world should be stopped");

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

      G1CollectedHeap* g1h = G1CollectedHeap::heap();

  {- -------------------------------------------
  (1) (変数宣言など)
      (処理の開始時間を記録しておく)
      ---------------------------------------- -}

      double start = os::elapsedTime();

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

      G1CollectorPolicy* g1p = G1CollectedHeap::heap()->g1_policy();

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

      g1p->record_concurrent_mark_init_start();
      checkpointRootsInitialPre();

      // YSR: when concurrent precleaning is in place, we'll
      // need to clear the cached card table here

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

      ResourceMark rm;
      HandleMark  hm;

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

      g1h->ensure_parsability(false);
      g1h->perm_gen()->save_marks();

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

      CMMarkRootsClosure notOlder(this, g1h, false);
      CMMarkRootsClosure older(this, g1h, true);

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

      g1h->set_marking_started();
      g1h->rem_set()->prepare_for_younger_refs_iterate(false);

  {- -------------------------------------------
  (1) CMMarkRootsClosure を引数として SharedHeap::process_strong_roots() を呼び出し, 
      strong root から辿り着けるオブジェクト全てに mark を付ける.
      ---------------------------------------- -}

      g1h->process_strong_roots(true,    // activate StrongRootsScope
                                false,   // fake perm gen collection
                                SharedHeap::SO_AllClasses,
                                &notOlder, // Regular roots
                                NULL,     // do not visit active blobs
                                &older    // Perm Gen Roots
                                );

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

      checkpointRootsInitialPost();

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

      // Statistics.
      double end = os::elapsedTime();
      _init_times.add((end - start) * 1000.0);

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

      g1p->record_concurrent_mark_init_end();
    }