Since installing Mac OS 10.5 I've been falling in love with dtrace. I'd like to have dtrace instrumentation built into Perl as standard. Last night I started playing around with Alan Burlison's experimental dtrace patch and in particular with Richard Dawe's modified version of Alan's patch.
I made some progress and got the patch to apply cleanly against bleadperl and made a couple of changes (simplifications actually) to correspond with how dtrace itself has evolved.
This morning it occurred to me that I might be able to add the dtrace probes to a replacement runops loop instead of making it a compile time option for Perl itself. As a result I've just released Devel::DTrace.
Having launched a Perl process like this
perl -MDevel::DTrace someprog.pl
you can attach to it with dtrace and watch the subroutine calls go by.
For the next release of Devel::DTrace I plan to have it build a custom probe-enabled interpreter, dtperl (which is quite simple) which will be nearly as good as having probes hard wired into Perl.
I'd still like to get dtrace into core but doing so depends on minimising the performance hit that's incurred. At the moment the probe code works out the subroutine name, file and line number for every entry and exit even if the probe is disabled. The recommended solution (as per Alan's article linked above) is to move that decode logic out of Perl and into dtrace - but that's not trivial because the code has to do different things depending on how Perl is built.
In the mean time if you have a system that supports dtrace please give Devel::DTrace a try.
