"Since the conclusion of the SMPng project, the focus of SMP development in FreeBSD has shifted from deploying locking infrastructure to careful profiling and optimization of kernel SMP strategies for increased performance on common workloads. FreeBSD 7.0 was the first release to benefit from this optimization work." The status of this work includes
MySQL workload benchmarks and
memory allocator performance in the new FreeBSD 8 branch. Also, here is a recent
presentation showing FreeBSD compared to several other operating systems like NetBSD, DrangonFly, Solaris, and Linux.