The hwpmc support Brendan's using here is in stock FreeBSD, but the default callchain capture depth is only 8 frames in FreeBSD 10.0, so you'd want to set in lo

The hwpmc support Brendan's using here is in stock FreeBSD, but the default callchain capture depth is only 8 frames in FreeBSD 10.0, so you'd want to set in loader.conf: kern.hwpmc.callchaindepth=32 The default is 32 in FreeBSD-Current and the upcoming 10.1 release.