// VM Thread interface for determining safepoint rate

  static long last_non_safepoint_interval() {

  {- -------------------------------------------
  (1) 現在時刻 (= os::javaTimeMillis() の値) から
      _end_of_last_safepoint の値を引いたものをリターン.

      (_end_of_last_safepoint は, 最後の Safepoint 処理が終わった時刻が記録されている.
       See: SafepointSynchronize::end())
      ---------------------------------------- -}

        return os::javaTimeMillis() - _end_of_last_safepoint;
      }