Github user ivmaykov commented on the issue:
https://github.com/apache/zookeeper/pull/669
@maoling it will be hard to do perf comparison of netty3 vs netty4 for us
because we are currently using the NIO transports, and we don't plan on
switching to netty3 in production. Comparing NIO vs netty4 is kind of
apples-and-oranges. A quick perf test with this patch showed that NIO to netty4
did not result in any obvious performance regressions, so I think we can say
they are at least comparable :)---
