NAME

Devel::Timer - Track and report execution time for parts of code

SYNOPSIS

  use Devel::Timer;

  my $t = Devel::Timer->new();

  $t->mark("first db query");

  ## do some work

  $t->mark("second db query");

  ## do some more work

  $t->mark("end of second db query");

  $t->report();

DESCRIPTION

Devel::Timer allows developers to accurately time how long a specific piece of code takes to execute. This can be helpful in locating the slowest parts of an existing application.

First, the Devel::Timer module is used and instantiated.

  use Devel::Timer;

  my $t = Devel::Timer->new();

Second, markers are placed before and after pieces of code that need to be timed. For this example, we are profiling the methods get_user_score() and get_average_user_score().

  $t->mark("first db query");
  &get_user_score($user);

  $t->mark("second db query");
  &get_average_user_score();

Finally, at the end of the code that you want to profile, and end marker is place, and a report is generated on stderr.

  $t->mark("END");
  $t->report();

Sample report:

  Devel::Timer Report -- Total time: 0.3464 secs
  Interval  Time    Percent
  ----------------------------------------------
  02 -> 03  0.3001  86.63%  second db query -> END
  01 -> 02  0.0461  13.30%  first db query -> second db query
  00 -> 01  0.0002   0.07%  INIT -> first db query

The report is output using the method Devel::Timer::print() which currently just prints to stderr. If you want to send the output to a custom location you can override the print() method. The initialize() and shutdown() methods can also overridden if you want to open and close log files or database connections.

METHODS

new

Create a new instance. No parameters are processed.

initialize

Empty method. Can be implemented in the subclass.

mark(NAME)

Set a timestamp with a NAME.

print

Prints to STDERR. Can be overridden in the subclass.

report

Prints the report to STDOUT. By default report() looks like this:

  $t->report;

  Devel::Timer Report -- Total time: 7.0028 secs
  Interval  Time    Percent
  ----------------------------------------------
  05 -> 06  3.0006  42.85%  something begin -> something end
  03 -> 04  2.0007  28.57%  something begin -> something end
  06 -> 07  1.0009  14.29%  something end -> END
  01 -> 02  1.0004  14.29%  something begin -> something end
  00 -> 01  0.0000   0.00%  INIT -> something begin
  04 -> 05  0.0000   0.00%  something end -> something begin
  02 -> 03  0.0000   0.00%  something end -> something begin

Which is great for small or non-iterative programs, but if there's hundreds of loops of "something begin -> something end" the report gets very painful very quickly. :)

In that scenario you might find collapse useful:

  $t->report(collapse => 1);

  Devel::Timer Report -- Total time: 7.0028 secs
  Count     Time    Percent
  ----------------------------------------------
         3  6.0018  85.71%  something begin -> something end
         1  1.0009  14.29%  something end -> END
         2  0.0001   0.00%  something end -> something begin
         1  0.0000   0.00%  INIT -> something begin

The stats for all combinations of labels are added together.

We also accept a sort_by parameter. By default the report is sorted by total time spent descending (like the default report()), but you can sort by count descending instead if you want:

  $t->report(collapse => 1, sort_by => 'count');

  Devel::Timer Report -- Total time: 7.0028 secs
  Count     Time    Percent
  ----------------------------------------------
         3  6.0018  85.71%  something begin -> something end
         2  0.0001   0.00%  something end -> something begin
         1  0.0000   0.00%  INIT -> something begin
         1  1.0009  14.29%  something end -> END

get_stats

Returns the accumulated statistics for a specific a combination of mark()'s that have occurred while your program ran. These values are the exact same statistics that report() prints. get_stats() simply returns them to you so you can do something creative with them.

For example, to get the cumulative stats for every time your program has specifically moved from mark("X") to mark("Y"), you can run this:

  my ($time, $percent, $count) = $t->get_stats("X", "Y");

$time is the total number of seconds elapsed between "X" and "Y".

$percent is the percentage of total program run time that you have spent between "X" and "Y".

$count is the number of times your program has moved from "X" to "Y".

shutdown

Empty method. Can be implemented in subclass.

SUBCLASSING

e.g.

package MyTimer;

use strict; use Devel::Timer; use vars qw(@ISA);

@ISA = ("Devel::Timer");

sub initialize { my $log = "/tmp/timer.log"; open(LOG, ">>$log") or die("Unable to open [$log] for writing."); }

sub print { my($self, $msg) = @_; print LOG $msg . "\n"; }

sub shutdown { close LOG; }

You would then use the new module MyTimer exactly as you would use Devel::Timer.

  use MyTimer;
  my $t = MyTimer->new();
  $t->mark("about to do x");
  $t->mark("about to do y");
  $t->mark("done y");
  $t->report();

TO DO

Devel::Timer does not currently do any reporting or statistics of any kind based on nested trees of mark() calls. So if your program runs these mark() calls:

  A 
    B, C
    B, C
  D
  E

Devel::Timer never tells you anything about how much time you spent moving from A to D. Depth aware reporting might be an interesting project to tackle.

COPYRIGHT

Jason Moore

This is free software. It is licensed under the same terms as Perl itself.

AUTHOR

  Author:      Jason Moore - jmoore@sober.com (no longer valid)
  Maintainer:  Gabor Szabo - gabor@pti.co.il
  Contributor: Jay Hannah  - jay@jays.net