manpagez: man pages & more
man Devel::DProf(3)
Home | html | info | man
Devel::DProf(3pm)      Perl Programmers Reference Guide      Devel::DProf(3pm)


       Devel::DProf - a Perl code profiler


               perl -d:DProf


       The Devel::DProf package is a Perl code profiler.  This will collect
       information on the execution time of a Perl script and of the subs in
       that script.  This information can be used to determine which
       subroutines are using the most time and which subroutines are being
       called most often.  This information can also be used to create an
       execution graph of the script, showing subroutine relationships.

       To profile a Perl script run the perl interpreter with the -d debugging
       switch.  The profiler uses the debugging hooks.  So to profile script the following command should be used:

               perl -d:DProf

       When the script terminates (or when the output buffer is filled) the
       profiler will dump the profile information to a file called tmon.out.
       A tool like dprofpp can be used to interpret the information which is
       in that profile.  The following command will print the top 15
       subroutines which used the most time:


       To print an execution graph of the subroutines in the script use the
       following command:

               dprofpp -T

       Consult dprofpp for other options.


       The old profile is a text file which looks like this:

               $XS_VERSION='DProf 19970606';
               # All values are given in HZ
               $rrun_utime=2; $rrun_stime=0; $rrun_rtime=7
               + 26 28 566822884 DynaLoader::import
               - 26 28 566822884 DynaLoader::import
               + 27 28 566822885 main::bar
               - 27 28 566822886 main::bar
               + 27 28 566822886 main::baz
               + 27 28 566822887 main::bar
               - 27 28 566822888 main::bar

       The first line is the magic number.  The second line is the hertz
       value, or clock ticks, of the machine where the profile was collected.
       The third line is the name and version identifier of the tool which
       created the profile.  The fourth line is a comment.  The fifth line
       contains three variables holding the user time, system time, and
       realtime of the process while it was being profiled.  The sixth line
       indicates the beginning of the sub entry/exit profile section.

       The columns in PART2 are:

               sub entry(+)/exit(-) mark
               app's user time at sub entry/exit mark, in ticks
               app's system time at sub entry/exit mark, in ticks
               app's realtime at sub entry/exit mark, in ticks
               fully-qualified sub name, when possible

       With newer perls another format is used, which may look like this:

               $XS_VERSION='DProf 19971213';
               # All values are given in HZ
               $over_utime=5917; $over_stime=0; $over_rtime=5917;
               $rrun_utime=1284; $rrun_stime=0; $rrun_rtime=1284;

               @ 406 0 406
               & 2 main bar
               + 2
               @ 456 0 456
               - 2
               @ 1 0 1
               & 3 main baz
               + 3
               @ 141 0 141
               + 2
               @ 141 0 141
               - 2
               @ 1 0 1
               & 4 main foo
               + 4
               @ 142 0 142
               + & Devel::DProf::write
               @ 5 0 5
               - & Devel::DProf::write

       (with high value of $ENV{PERL_DPROF_TICKS}).

       New "$over_*" values show the measured overhead of making $over_tests
       calls to the profiler These values are used by the profiler to subtract
       the overhead from the runtimes.

       Lines starting with "@" mark the amount of time passed since the
       previous "@" line.  The numbers following the "@" are integer tick
       counts representing user, system, and real time.  Divide these numbers
       by the $hz value in the header to get seconds.

       Lines starting with "&" map subroutine identifiers (an integer) to
       subroutine packages and names.  These should only occur once per

       Lines starting with "+" or "-" mark normal entering and exit of
       subroutines.  The number following is a reference to a subroutine

       Lines starting with "*" mark where subroutines are entered by "goto
       &subr", but note that the return will still be marked as coming from
       the original sub.  The sequence might look like this:

               + 5
               * 6
               - 5

       Lines starting with "/" is like "-" but mark where subroutines are
       exited by dying.  Example:

               + 5
               + 6
               / 6
               / 5

       Finally you might find "@" time stamp marks surrounded by "+ &
       Devel::DProf::write" and "- & Devel::DProf::write" lines.  These 3
       lines are outputted when printing of the mark above actually consumed
       measurable time.


       When Devel::DProf finds a call to an &AUTOLOAD subroutine it looks at
       the $AUTOLOAD variable to find the real name of the sub being called.
       See "Autoloading" in perlsub.


       "PERL_DPROF_BUFFER" sets size of output buffer in words.  Defaults to

       "PERL_DPROF_TICKS" sets number of ticks per second on some systems
       where a replacement for times() is used.  Defaults to the value of "HZ"

       "PERL_DPROF_OUT_FILE_NAME" sets the name of the output file.  If not
       set, defaults to tmon.out.


       Builtin functions cannot be measured by Devel::DProf.

       With a newer Perl DProf relies on the fact that the numeric slot of
       $DB::sub contains an address of a subroutine.  Excessive manipulation
       of this variable may overwrite this slot, as in

         $DB::sub = 'current_sub';
         $addr = $DB::sub + 0;

       will set this numeric slot to numeric value of the string
       "current_sub", i.e., to 0.  This will cause a segfault on the exit from
       this subroutine.  Note that the first assignment above does not change
       the numeric slot (it will mark it as invalid, but will not write over

       Another problem is that if a subroutine exits using goto(LABEL),
       last(LABEL) or next(LABEL) then perl may crash or Devel::DProf will die
       with the error:

          panic: Devel::DProf inconsistent subroutine return

       For example, this code will break under Devel::DProf:

          sub foo {
            last FOO;
          FOO: {

       A pattern like this is used by Test::More's skip() function, for
       example.  See perldiag for more details.

       Mail bug reports and feature requests to the perl5-porters mailing list
       at <>.


       perl(1), dprofpp(1), times(2)

perl v5.10.0                      2007-12-18                 Devel::DProf(3pm)

Mac OS X 10.6 - Generated Thu Sep 17 20:11:35 CDT 2009
© 2000-2024
Individual documents may contain additional copyright information.