Ralph, you may want to look back at the archives. Michal and I think Justin had posted an extensive discussion on how to identify and pin cpus. See:
http://mailman.icsi.berkeley.edu/pipermail/bro/2016-October/010743.html
The suggested lstopo is a very good way to enumerate your cores, as indicated in that thread.
Also, regarding 32 workers, we are handling 6Gb/s traffic with af_packet with just 18 workers, minimum memory usage, but fairly high rate of cpu usage. Our drop rate is under .5% across all workers.
Lastly, read the Bro bit here:
We have found that this is indeed fairly accurate with regards to worker count and pps consumption by bro.