void GenCollectedHeap::collect(GCCause::Cause cause) {

  {- -------------------------------------------
  (1) CMS でかつ条件が満たされていれば, GenCollectedHeap::collect_mostly_concurrent() を呼び出す
      (See: GenCollectedHeap::should_do_concurrent_full_gc)
      そうでなければ, GenCollectedHeap::collect() を呼び出す.
        (なお, 呼び出し元が GCCause::_scavenge_alot の場合のみ Minor GC とする. 他の場合は Full GC)
      ---------------------------------------- -}

      if (should_do_concurrent_full_gc(cause)) {
    #ifndef SERIALGC
        // mostly concurrent full collection
        collect_mostly_concurrent(cause);
    #else  // SERIALGC
        ShouldNotReachHere();
    #endif // SERIALGC
      } else {
    #ifdef ASSERT
        if (cause == GCCause::_scavenge_alot) {
          // minor collection only
          collect(cause, 0);
        } else {
          // Stop-the-world full collection
          collect(cause, n_gens() - 1);
        }
    #else
        // Stop-the-world full collection
        collect(cause, n_gens() - 1);
    #endif
      }
    }