trident partitionBy dramatically low down the thoughput？

[vlhf刘海峰 <hf...@Ctrip.com>]

As I tested in local mode，with or without partitionBy, the throughputs are quit different, I saw partitionBy dramatically low down the throughput. That surprised me, as I thought partitionBy may cause  higher latency but should do nothing with throughput. Is that normal or I should check my test?