The PmcTools project now has a new discussion group pmctools-discuss, hosted on groups.google.com.
If you have a question on how to use PmcTools, or about its internals, please ask it there.
In April 2009 I was invited to speak on FreeBSD/PmcTools by the Bangalore chapter of the ACM. The slides for this talk are available at: http://people.freebsd.org/~jkoshy/download/acm-apr-09.pdf (550KB, PDF).
This was an overview talk. The talk briefly touched upon: the motivations and goals of the project, the programming APIs, some aspects of the implementation and on possible future work.
A couple of (lagged!) updates on my FreeBSD/PmcTools work:
More recently, Nokia, via Jeff Roberson, contributed basic support for the PMCs in the Core/i7™ CPU, the next member in the Core™ family of CPUs (SVN #187761).
With these additions PmcTools supports most Intel CPUs that have PMCs in them. (I have plans to finish support for 166Mhz Pentium MMX™ CPUs soon.)
A couple of tricky bugs were tracked down and fixed:
The NMI handler code I had written for the amd64 architecture needed to be more robust than it was. Fixed in SVN #188065.
A bug in callchain capture code that would appear only under high loads and only on SMP machines. Fixed in SVN #186037.
Thanks to Artem Belevich, Fabien Thomas, George Neville-Neil and Jeff Roberson for their assistance with debugging.