NAME
   Devel::SmallProf - per-line Perl profiler

SYNOPSIS
           perl5 -d:SmallProf test.pl

DESCRIPTION
   The Devel::SmallProf profiler is focused on the time taken for a program
   run on a line-by-line basis. It is intended to be as "small" in terms of
   impact on the speed and memory usage of the profiled program as possible
   and also in terms of being simple to use. Those statistics are placed in
   the file smallprof.out in the following format:

           <num> <time> <ctime> <line>:<text>

   where <num> is the number of times that the line was executed, <time> is
   the amount of "wall time" (time according the the clock on the wall vs.
   cpu time) spent executing it, <ctime> is the amount of cpu time expended
   on it and <line> and <text> are the line number and the actual text of
   the executed line (read from the file).

   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 -k 2nr,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
   *   The "wall time" readings come from Time::HiRes and are reasonably
       useful, at least on my system. The cpu times come from the 'times'
       built-in and the granularity is not necessarily as small as with the
       wall time. On some systems this column may be useful. On others it
       may not.

   *   SmallProf does attempt to make up for its shortcomings by subtracting a
       small amount from each timing (null time compensation). This should
       help somewhat with the accuracy.

   *   SmallProf depends on the Time::HiRes package to do its timings. It
       claims to require version 1.20, but may work with earlier versions,
       depending on your platform.

OPTIONS
   SmallProf has 3 variables which can be used during your script to affect
   what gets profiled.

   *   If you do not wish to see lines which were never called, set the
       variable `$DB::drop_zeros = 1'. With `drop_zeros' set, SmallProf can
       be used for basic coverage analysis.

   *   To turn off profiling for a time, insert a `$DB::profile = 0' into your
       code (profiling may be turned back on with `$DB::profile = 1'). All
       of the time between profiling being turned off and back on again
       will be lumped together and reported on the `$DB::profile = 0' line.
       This can be used to summarize a subroutine call or a chunk of code.

   *   To only profile code in a certain package, set the `%DB::packages'
       array. For example, to see only the code in packages `main' and
       `Test1', do this:

               %DB::packages = ( 'main' => 1, 'Test1' => 1 );

   *   These variables can be put in a file called .smallprof in the current
       directory. For example, a .smallprof containing

               $DB::drop_zeros = 1;
               $DB::profile = 0;

       will set SmallProf to not report lines which are never touched for
       any file profiled in that directory and will set profiling off
       initially (presumably to be turned on only for a small portion of
       code).

INSTALLATION
   Just the usual

           perl Makefile.PL
           make
           make test
           make install

   and should install fine via the CPAN module.

BUGS
   Subroutine calls are currently not under the control of %DB::packages.
   This should not be a great inconvenience in general.

   The handling of evals is bad news. This is due to Perl's handling of
   evals under the -d flag. For certain evals, caller() returns '(eval n)'
   for the filename and for others it doesn't. For some of those which it
   does, the array `@{'_<filename'}' contains the code of the eval. For
   others it doesn't. Sometime, when I've an extra tuit or two, I'll figure
   out why and how I can compensate for this.

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

AUTHOR

Ted Ashton <[email protected]>

SmallProf was developed from code originally posted to usenet by Philippe
Verdret <[email protected]>.  Special thanks to
Geoffrey Broadwell <[email protected]> for his assistance on the
Win32 platform and to Philippe for his patient assistance in testing and
debugging.

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
   the Devel::DProf manpage, the Time::HiRes manpage.

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