While OS X doesn't have something like Linux's NUMA interface to explicitly lock a thread to a core, 10.5 shipped a thread affinity API which allows you to help the scheduler make better placement decisions:
“OS X does not export interfaces that identify processors or control thread placement—explicit thread to processor binding is not supported. Instead, the kernel manages all thread placement. Applications expect that the scheduler will, under most circumstances, run its threads using a good processor placement with respect to cache affinity.
However, the application itself knows the detailed caching characteristics of its threads and its data—in particular, the organization of threads as disjoint sets characterized by their association with (affinity to) distinct shared data.
While threads within such a set exhibit affinity with each other via shared data, they share a disaffinity or negative affinity with respect to other sets. In other words, a set expresses an affinity with an L2 cache and the scheduler should seek to run threads in a set on processors sharing that L2 cache.”
https://developer.apple.com/library/mac/releasenotes/Perform...
