Github user sihuazhou commented on the issue:
https://github.com/apache/flink/pull/5465
Aha, for now I would like to leave it to 128 ... Even I can't find a best
value, but this value is not a bad value and is also a safety value.. If I
found any another value that is better than it (on production), I will feed
back to community at that time.---
