FAQ 3.6 How do I profile my Perl programs?

PerlFAQ Server · *nix forums Guru Joined: 09 Apr 2005 Posts: 1008

This is an excerpt from the latest version perlfaq3.pod, which
comes with the standard Perl distribution. These postings aim to
reduce the number of repeated questions as well as allow the community
to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .

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3.6: How do I profile my Perl programs?

You should get the Devel::DProf module from the standard distribution
(or separately on CPAN) and also use Benchmark.pm from the standard
distribution. The Benchmark module lets you time specific portions of
your code, while Devel::DProf gives detailed breakdowns of where your
code spends its time.

Here's a sample use of Benchmark:

use Benchmark;

@junk = `cat /etc/motd`;
$count = 10_000;

timethese($count, {
'map' => sub { my @a = @junk;
map { s/a/b/ } @a;
return @a },
'for' => sub { my @a = @junk;
for (@a) { s/a/b/ };
return @a },
});

This is what it prints (on one machine--your results will be dependent
on your hardware, operating system, and the load on your machine):

Benchmark: timing 10000 iterations of for, map...
for: 4 secs ( 3.97 usr 0.01 sys = 3.98 cpu)
map: 6 secs ( 4.97 usr 0.00 sys = 4.97 cpu)

Be aware that a good benchmark is very hard to write. It only tests the
data you give it and proves little about the differing complexities of
contrasting algorithms.

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