public LlapFileSystemStatisticsData subtract(LlapFileSystemStatisticsData other) {
      if (other == null){
        return this;
      }
      this.bytesRead -= other.bytesRead;
      this.bytesWritten -= other.bytesWritten;
      this.readOps -= other.readOps;
      this.largeReadOps -= other.largeReadOps;
      this.writeOps -= other.writeOps;
      return this;
    }
Convenience class over Hadoop's FileSystem.Statistics.StatisticsData.
Unfortunately, neither the fields, nor the convenience methods (e.g. StatisticsData.add, StatisticsData.negate)
are available here as they are package protected, so we cannot reuse them.
llap-common/src/java/org/apache/hadoop/hive/llap/LlapThreadLocalStatistics.java