The main differences are that NetBSD scales O(1) on forking new
processes while FreeBSD scales O(n). For memory mapping and socket
creation both scale O(1) but NetBSD is twice as fast as FreeBSD
But for binding addresses to sockets, FreeBSD scales O(1) while
NetBSD scales O(n) but is twice as fast for a small number of bound
sockets. Also for POSIX thread creation FreeBSD scales O(1) while
NetBSD scales something like O(n) and is twice as fast for a small
number of threads.
This paper has presented a suite of benchmarks and results for comparing the performance of NetBSD 2.0 and FreeBSD 5.3 in the areas of core operating system functionality, network scalability and thread performance.
The results clearly indicate that recent architectural decisions in the NetBSD operating system have closed the performance gap between NetBSD and FreeBSD. In fact, NetBSD has surpassed FreeBSD in performance in the areas investigated in this paper. Significant performance improvements are obviously visible in the thread implementation.