Performance Issues Running Cpp Runtime on Many Threads

[wangtao9]

When I use the Cpp parser in multiple threads (around 30+), the performance drops a lot compared to using a single thread.

I'm guessing it's the lock/mutex, so I simply removed all locks and re-tested, and it did run a lot faster.

But removing locks makes the parser no longer thread-safe, I would like to ask is there any way to improve the performance of multi-threaded parser?

[andreasbuhr]

@wangtao9 is this solved as #4237 is merged?