@Override
    public synchronized GcData clone() {
      try {
        return (GcData) super.clone();
      } catch (CloneNotSupportedException e) {
        throw new RuntimeException(e);
      }
    }
Returns the percentage (0..100) of time that the JVM spent in GC pauses within the
observation window of the associated GCTimeMonitor.

@return GcTimePercentage.
iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/service/metric/JvmGcMonitorMetrics.java