== create the usbpf tap clone (root), NO bpf listener attached ==
usbus0: flags=800001<UP,PROXY> metric 0 mtu 0
	groups: usbus
== run the tap-cost rig ==
== cleanup ==
RUN_DONE
HAMMER2: INITIATE SPANs
swap low/high-water marks set to 41940/62910
DF5531: bus ifp=0xfffff80118725ac0 if_bpf=0 (expect NULL: no listener)
DF5531: payload=4096 bytes, 20000 iters
DF5531: (A) ifp set,   if_bpf==NULL : 1256 cycles/call
DF5531: (B) ifp NULL (early-return) : 34 cycles/call
DF5531: overhead ratio A/B          : 36.2 x
TAP_RESULT=done