protected static byte[][] getSplits(TestOptions opts) {
    if (opts.presplitRegions == DEFAULT_OPTS.presplitRegions) return null;

    int numSplitPoints = opts.presplitRegions - 1;
    byte[][] splits = new byte[numSplitPoints][];
    long jump = opts.totalRows / opts.presplitRegions;
    for (int i = 0; i < numSplitPoints; i++) {
      long rowkey = jump * (1 + i);
      splits[i] = format(rowkey);
    }
    return splits;
  }
generates splits based on total number of rows and specified split regions
hbase-diagnostics/src/main/java/org/apache/hadoop/hbase/PerformanceEvaluation.java