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 <ashted@southern.edu>
 
SmallProf was developed from code originally posted to usenet by Philippe
Verdret <philippe.verdret@sonovision-itep.fr>.  Special thanks to
Geoffrey Broadwell <habusan2@sprynet.com> 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.

