public static long computeKVMemUsageInMap(final String key, final @Nonnull Binary value) {
    return 40L + estimateStringSize(key) + value.ramBytesUsed();
  }
The basic memory occupied by any BasicMNode object.

<ol>
  <li>MapEntry in parent
      <ol>
        <li>key reference, 8B
        <li>value reference, 8B
        <li>entry size, see ConcurrentHashMap.Node, 28
      </ol>
</ol>
iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/schema/MemUsageUtil.java