vm.pmap.pti=0 performance regression

[Slawa Olhovchenkov]

I am try to do different benchmark for my application (NETMAP based
packet filtering) and see strange behavior:

vm.pmap.pti=0
machdep.hyperthreading_allowed=0

caused performance drop about 20% on network thread. In case of

vm.pmap.pti=1
machdep.hyperthreading_allowed=0

or

vm.pmap.pti=1
SMT=off in bios

or

vm.pmap.pti=0
SMT=off in bios

performance about same and high about 20%.

How does that work?