[syslog-ng] Syslog-ng 3.4 ans json output.

I am looking at the json output module and am wondering on how fast it should run. From what I have tested, it can only handle a sustained stream of approx 2,500 - 3,000 messages per second. This seems too slow to me, so I ask others if anyone is having a problem with the performance of the json output macro. To the developers - is this expected? It seems to be the same speed under 3.3 and 3.4. Evan.