// Allocation. We report all successful allocations to the size policy
// Note that the perm gen does not use this method, and should not!

HeapWord* PSOldGen::allocate(size_t word_size, bool is_tlab) {

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

      assert_locked_or_safepoint(Heap_lock);

  {- -------------------------------------------
  (1) まずは PSOldGen::allocate_noexpand() で確保を試みる.
      ---------------------------------------- -}

      HeapWord* res = allocate_noexpand(word_size, is_tlab);

  {- -------------------------------------------
  (1) 成功しなければ PSOldGen::expand_and_allocate() で確保を試みる.
      ---------------------------------------- -}

      if (res == NULL) {
        res = expand_and_allocate(word_size, is_tlab);
      }

  {- -------------------------------------------
  (1) 確保が成功した場合は, PSAdaptiveSizePolicy::tenured_allocation() を呼び出して成功したことを報告しておく.
      ---------------------------------------- -}

      // Allocations in the old generation need to be reported
      if (res != NULL) {
        ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
        heap->size_policy()->tenured_allocation(word_size);
      }

  {- -------------------------------------------
  (1) 結果をリターン
      ---------------------------------------- -}

      return res;
    }