It applies to more than DBs. Running VoIP software, we found that just by setting CPU affinity, we got a major increase in performance. The software in question, FreeSWITCH, is inanely-threaded in a misguided believe that "more threads=more performance" (well that, and it's also just easier to program). When there's thousands of threads going, keeping them and their data local to one NUMA node or less really makes a huge difference.