I have tested with

jackd -P 90 -d alsa -p 256 -n 2
jack_netsource -n 3 -H xxxx

jackd -P 90 -d netone -n 3
zita-a2j -p 128 -n 3
zita-j2a -p 128 -n 3 and zita-j2a -p 256 -n 3
jackminimix

Every process in the list is in audio cgroup that allocates 95% of CPU time to realtime threads to members.

Did I configure -p improperly?