NAME

Devel::SmallProf - a small Perl profiler

SYNOPSIS

perl5 -d:SmallProf test.pl

DESCRIPTION

The Devel::SmallProf is a small profiler which I find useful (or at least interesting :-) when used in conjuction with Devel::DProf. It collects statistics on the run times of the lines in the various files being run. Those statistics are placed in the file smallprof.out in one of two formats. If $DB::print_lines is false (the default), it prints:

<num> <time> <file>:<line>

where <num> is the number of times that the line was executed, <time> is the amount of time spent executing it and <file> and <line> are the filename and line number, respectively.

If, on the other hand, $DB::print_lines is true, it print:

<num> <time> <text>

where <num> and <time> are as above and <text> is the actual text of the executed line (read from the file). If the executed line, however, is in an eval, no line is printed.

The package uses the debugging hooks in Perl and thus needs the -d switch, so to profile test.pl, use the command:

perl5 -d:SmallProf test.pl

Once the script is done, the statistics in smallprof.out can be sorted to show which lines took the most time. The output can be sorted to find which lines take the longest, either with the sort command:

sort -nrk 2 smallprof.out | less

or a perl script:

	open(PROF,"smallprof.out");
	@sorted = sort {(split(/\s+/,$b))[2] <=> 
                        (split(/\s+/,$a))[2]} <PROF>;
        close PROF;
	print join('',@sorted);

NOTES

• Determining the accuracy or signifiance of the results is left as an exercise for the reader. I've tried to keep the timings pretty much just to the profiled code, but no guarantees of any kind are made.

• SmallProf depends on syscall() and gettimeofday() (see "syscall" in perlfunc) to do its timings. If your system lacks them SmallProf won't work.

• There is a variable called $DB::profile_evals which sets up some code to try to help the programmer evaluate *which* eval is taking all the time. You can activate this code by putting a BEGIN{$DB::profile_evals =1} at the beginning of your script. It is not clear whether this should be considered a feature or a bug. See "BUGS".

BUGS

The handling of evals is poor. The results, even with $DB::profile_evals on, are ugly. The code to handle $DB::profile_evals is even uglier. The eval profiling uses the @{"main::_<$filename"} array to find the code which is currently being executed. I expect that things could be improved somewhat by dealing appropriately with packages, but the reference in perldebug calls it only @{"_<$filename"}. As it is, the eval lines reported are blank some of the time. Even when they show up, it can be hard to tell where they originated.

Also, there has got to be a better way to switch that stuff on and off than "bootstrapping" &DB::DB. If there is a slick, computationally cheap way of dealing with evals, I'm intending to set it to always debug evals and try to forget that I ever wrote kludge that is there now, but it's there now because I'm trying to keep the expense of this module as low as possible.

Comments, advice and insulting remarks about kludges are welcome. If you see inefficent stuff in this module and have a better way, please let me know.

AUTHOR

Ted Ashton <ashted@southern.edu>

SmallProf was developed from code orignally posted to usenet by Philippe Verdret. I've attempted to contact him but have had no success.

Copyright (c) 1997 Ted Ashton

This module is free software and can be redistributed and/or modified under the same terms as Perl itself.

SEE ALSO

Devel::DProf, gettimeofday()