I noticed that there's a "sort -u /tmp/current_arp_table6.txt" process that is often shooting up in terms of CPU usage on my opnsense, so I checked the size of the file.
it appears there is 110 unique entries (checked using "sort /tmp/current_arp_table6.txt | uniq | wc -l") but there is 1.7 millions lines in total, so there's some cleanup not working.
Any idea where I can do some manual cleanup to start?
Already found the culprit, I think. Seems OPN-Arp is causing this, the file stops growing when I stop the service.