public double calculateChunkHitRatio() {
    return lruCache.stats().hitRate();
  }
This class is used to cache <code>Chunk</code> of <code>ChunkMetaData</code> in IoTDB. The
caching strategy is LRU.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/buffer/ChunkCache.java