DistributedInformation

I’ve been promising myself some time to try out DTrace on TWiki’s codebase for over a year. By following Bryan Allen’s
instructions using Richard Dawe’s adaption of Alan Burlison’s work… I now have a Perl 5.8.8 with DTrace probes.

Sounds great, except for one thing…. I now have to learn enough about DTrace to use it The patch that Alan and Richard have (or at least their DTrace scripts) seem to require a priori knowledge of the Perl process’ pid… not something thats going to work out for what I want to do.

For a quick test, DTrace -c ./view -s /export/home/sven/src/dtrace/subs-tree.d does show the program flow.

The following is while running some perl scripts - the 2 numbers are their pids.

# dtrace -l | grep -i perl

17803  perl17669        libperl.so                      Perl_pp_sort sub-entry

17804  perl17669        libperl.so                   Perl_pp_dbstate sub-entry

17805  perl17669        libperl.so                  Perl_pp_entersub sub-entry

17806  perl17669        libperl.so                      Perl_pp_last sub-return

17807  perl17669        libperl.so                    Perl_pp_return sub-return

17808  perl17669        libperl.so                     Perl_dounwind sub-return

17809  perl17669        libperl.so                Perl_pp_leavesublv sub-return

17810  perl17669        libperl.so                  Perl_pp_leavesub sub-return

88501  perl17760        libperl.so                      Perl_pp_sort sub-entry

88502  perl17760        libperl.so                   Perl_pp_dbstate sub-entry

88503  perl17760        libperl.so                  Perl_pp_entersub sub-entry

88504  perl17760        libperl.so                      Perl_pp_last sub-return

88505  perl17760        libperl.so                    Perl_pp_return sub-return

88506  perl17760        libperl.so                     Perl_dounwind sub-return

88507  perl17760        libperl.so                Perl_pp_leavesublv sub-return

88508  perl17760        libperl.so                  Perl_pp_leavesub sub-return

so… first ignorant modification - in subs-tree.d, it wants to trace perl$target:::sub-entry - change that to perl*:::sub-entry, and of course, it works exactly as I want - attaches to all subsequent perl process (running my dtrace-perl build) and tells me whats going on. The only caveat being that the DTrace script will only start if there is a Perl process running - the provider is obviously not persistent.

Brilliant!

Should be a fun Christmas holiday adventure - 410 pages of dtrace book, and a myriad of web pages to consume and digest.