static long generateRandomRow(final long totalRows) {
    return ThreadLocalRandom.current().nextLong(Long.MAX_VALUE) % totalRows;
  }
Compute a throughput rate in MB/s.
@param rows   Number of records consumed.
@param timeMs Time taken in milliseconds.
@return String value with label, ie '123.76 MB/s'
hbase-diagnostics/src/main/java/org/apache/hadoop/hbase/PerformanceEvaluation.java