CEF module: seems slow?

```
% time nc localhost 5000 < firewall_cef.log
nc localhost 5000 < firewall_cef.log 0.02s user 0.01s system 0% cpu 8.214 total

% wc -l firewall_cef.log
8064 firewall_cef.log
```

Took 8.2 seconds to write 8000 lines to Logstash. 1000 events-per-second is pretty slow, in my expectation. Can we improve this?

This test was done on my laptop with all services hosted locally.