profiling - How do I profile my Perl programs?

Question

I need to improve the performance of my Perl application. How can I find the slow spots?

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Answer 1

(This is the official perlfaq answer, minus any subsequent edits)

The Devel namespace has several modules which you can use to profile your Perl programs. The Devel::DProf module comes with Perl and you can invoke it with the -d switch:

$ perl -d:DProf program.pl

After running your program under DProf, you'll get a tmon.out file with the profile data. To look at the data, you can turn it into a human-readable report with the dprofpp program that comes with Devel::DProf:

$ dprofpp

You can also do the profiling and reporting in one step with the -p switch to dprofpp:

$ dprofpp -p program.pl

The Devel::NYTProf (New York Times Profiler) does both statement and subroutine profiling. It's available from CPAN and you also invoke it with the -d switch:

$ perl -d:NYTProf some_perl.pl

Like DProf, it creates a database of the profile information that you can turn into reports. The nytprofhtml command turns the data into an HTML report similar to the Devel::Cover report:

$ nytprofhtml

CPAN has several other profilers that you can invoke in the same fashion. You might also be interested in using the C to measure and compare code snippets.

You can read more about profiling in Programming Perl, chapter 20, or Mastering Perl, chapter 5.

perldebguts documents creating a custom debugger if you need to create a special sort of profiler. brian d foy describes the process in The Perl Journal, "Creating a Perl Debugger", and "Profiling in Perl".

Perl.com has two interesting articles on profiling: "Profiling Perl", by Simon Cozens, and "Debugging and Profiling mod_perl Applications", by Frank Wiles.

Randal L. Schwartz writes about profiling in "Speeding up Your Perl Programs" for Unix Review and "Profiling in Template Toolkit via Overriding" for Linux Magazine.