public double getIOTimePerHit() {
    long time = ioHitTime.sum() / NANO_TIME;
    long count = ioHitCount.sum();
    return ((float) time / (float) count);
  }
Class that implements cache metrics for bucket cache.
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/bucket/BucketCacheStats.java