DTrace on FreeBSD
FreeBSD includes a substantial port of DTrace: an advanced event-based performance analysis and troubleshooting tool. DTrace can help you identify and quantify the root cause of virtually any performance issue, in both user-level and kernel code. It can be executed using custom and powerful one-liners and scripts.
Learn DTrace for FreeBSD in 12 easy lessons: /Tutorial
A library of handy DTrace one-liners: /One-Liners
Useful examples for kernel performance or functional analysis: /Examples
Adding support to the FreeBSD kernel: /KernelSupport
Howto add SDT probes to DTrace in the kernel: /HowToAddSDTProbes
The Dynamic Tracing Guide (aka DTrace Guide) is the language and provider reference. Currently focuses on illumos DTrace.
FreeBSD Handbook section on DTrace: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/dtrace.html
The website, which includes scripts, for the Prentice Hall 2011 book: DTrace: Dynamic Tracing in Oracle Solaris, Mac OS X, and FreeBSD
USENIX 2004 paper on DTrace: Dynamic Instrumentation of Production Systems
ACM Queue 2006 article: Hidden in Plain Sight
DTrace Review in Google tech talks (2007)
jb@'s 2008 BSDCan presentation: dtrace_bsdcan2008_jb.pdf