The Perl Profiler (Perl in a Nutshell, 2nd Edition)

6.5. The Perl Profiler

You can supply an alternative debugger for Perl to run by invoking your script with the -d:module switch. One of the most popular alternative debuggers for Perl is DProf, the Perl profiler. As of this writing, DProf is not included with the standard Perl distribution, but it is expected to be included soon.

Meanwhile, you can fetch the Devel::DProf module from CPAN. Once it has been properly installed on your system, you can use it to profile the Perl program in testpgm by typing:

perl -d:DProf testpgm

As your script runs, DProf gathers profile information. When the script terminates, the profiler dumps the gathered information to a file called tmon.out. A tool such as dprofpp, which is supplied with the Devel::DProf package, can be run to interpret the profile. If you run dprofpp against the tmon.out file created by DProf in the example above, you'll see something like the following:

% dprofpp tmon.out
Total Elapsed Time =    0.15 Seconds
  User+System Time =     0.1 Seconds
Exclusive Times
%Time Seconds     # Calls sec/call Name
 30.0   0.030          1   0.0300 Text::Wrap::CODE(0x175f08)
 20.0   0.020          1   0.0200 main::CODE(0xc7880)
 20.0   0.020          1   0.0200 main::CODE(0xfe480)
 10.0   0.010          1   0.0100 Text::Wrap::CODE(0x17151c)
 10.0   0.010         10   0.0010 Text::Tabs::expand
 0.00   0.000          1   0.0000 lib::CODE(0xfe5b8)
 0.00   0.000          3   0.0000 Exporter::export
 0.00   0.000          1   0.0000 Config::FETCH
 0.00   0.000          1   0.0000 lib::import
 0.00   0.000          1   0.0000 Text::Wrap::CODE(0x171438)
 0.00   0.000          3   0.0000 vars::import
 0.00   0.000          3   0.0000 Exporter::import
 0.00   0.000          2   0.0000 strict::import
 0.00   0.000          1   0.0000 Text::Wrap::CODE(0x171684)
 0.00   0.000          1   0.0000 lib::CODE(0xfe4d4)

The output shows the 15 subroutines that use the most time; you can then focus your efforts on those subroutines where tuning the code will have the greatest effect. This output is an example of running the dprofpp command with the default option set. The following are the options that are available:

-a


6.4. Customizing the Debugger		6.6. The perlbug Program