bool LowMemoryDetector::has_pending_requests() {

  {- -------------------------------------------
  (1) 全ての MemoryPool を辿り, 
      それらに対応づけられている usage sensor および gc usage sensor を
      SensorInfo::has_pending_requests() で調べていく.

      これらの sensor の中に一つでも pending 状態の通知が存在していれば true を返す.
      ---------------------------------------- -}

      assert(Service_lock->owned_by_self(), "Must own Service_lock");
      bool has_requests = false;
      int num_memory_pools = MemoryService::num_memory_pools();
      for (int i = 0; i < num_memory_pools; i++) {
        MemoryPool* pool = MemoryService::get_memory_pool(i);
        SensorInfo* sensor = pool->usage_sensor();
        if (sensor != NULL) {
          has_requests = has_requests || sensor->has_pending_requests();
        }

        SensorInfo* gc_sensor = pool->gc_usage_sensor();
        if (gc_sensor != NULL) {
          has_requests = has_requests || gc_sensor->has_pending_requests();
        }
      }
      return has_requests;
    }