openbsd might want a different sysctl for counting cpus.

[icepic]

sysctl hw|egrep '(ncpu|smt)'

hw.ncpu=8
hw.ncpufound=8
hw.ncpuonline=4

In case of hyperthreading, obsd might not activate all found threads and only have the scheduler use the "real" cores.
For better or worse, but ncpuonline=X is probably the sysctl you should use.