@Override
  protected double cost() {
    double cost = 0;
    for (int tableIdx = 0; tableIdx < cluster.numTables; tableIdx++) {
      cost += costsPerTable[tableIdx].cost();
    }
    return cost;
  }
Compute the cost of a potential cluster configuration based upon how evenly distributed tables
are.
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/TableSkewCostFunction.java