@Override
      public int compare(ServerAndLoad s1, ServerAndLoad s2) {
        if (s1.getLoad() == s2.getLoad()) {
          return 0;
        } else {
          return (s1.getLoad() > s2.getLoad()) ? 1 : -1;
        }
      }
If we need to balanceoverall, we need to add one more round to peel off one region from each
max. Together with other regions left to be assigned, we distribute all regionToMove, to the RS
that have less regions in whole cluster scope.
hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/SimpleLoadBalancer.java