OpenShift started to use up to 4 threads in northd [0] about a year ago. There is ongoing work for 17.1 adding this capability [1] in tripleo-ansible [2] and tripleo-heat-templates [3].

This feature should remove northd as a bottleneck in OVN performance. It should just involve adding a variable for the number of threads and passing it to ovn-ctl when it starts ovn-northd.

[0] https://github.com/openshift/cluster-network-operator/pull/1471
[1] https://bugzilla.redhat.com/show_bug.cgi?id=2213566
[2] https://code.engineering.redhat.com/gerrit/c/tripleo-ansible/+/447943/
[3] https://code.engineering.redhat.com/gerrit/c/openstack-tripleo-heat-templates/+/447941/