Devel::SmallProf - per-line Perl profiler

            perl5 -d:SmallProf

    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, use the command:

            perl5 -d:SmallProf

    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:

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

    *   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.

    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

    Just the usual

            perl Makefile.PL
            make test
            make install

    and should install fine via the CPAN module.

    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. (Note: 5.6.0 made some
    debugging changes. This may now be fixed, I'm not sure).

    SmallProf must be invoked from the command line. If it is included on
    the shebang line, the file in which it is included will not be visible
    in the symbol table. Profiling will continue as expected, but the
    contents of the source lines will not be listed. This is new as of

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

    Devel::SmallProf was developed by Ted Ashton <>. It is
    currently being maintained by Salvador Fandiño <>.

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

    Copyright (c) 1997-2000 Ted Ashton

    Copyright (c) 2003 Salvador Fandiño

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

    Devel::DProf, Time::HiRes.