the cost of respToken in respHandler is much higher than expected

[chgz]

Observed behavior

In a simple subscription service, about 70k/s qps.
Observed through pprof, the cost of respToken in respHandler is much higher than expected.
I'm not using any wildcard topics, it's all fixed topics.

Expected behavior

less overhead here

Server and client version

github.com/nats-io/nats-server/v2 v2.8.4
github.com/nats-io/nats.go v1.27.1

This part of the code is the same as the latest version.

Host environment

Linux x64
Centos 7.3

Steps to reproduce

[piotrpio]

Hello @chgz, thanks for creating the issue. I'll see if there's a good way to optimize it, we have to verify the subject in respToken though.

[chgz]

Thanks for your reply.
Looking forward to good news.