


ext::Devel-DProf:PerloProgrammers Refeext::Devel-DProf::DProf(3p)


NAME
       Devel::DProf - a Perl code profiler

SYNOPSIS
               perl -d:DProf test.pl

DESCRIPTION
       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 test.pl the following command
       should be used:

               perl -d:DProf test.pl

       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:

               dprofpp

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

               dprofpp -T

       Consult dprofpp for other options.

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

               #fOrTyTwO
               $hz=100;
               $XS_VERSION='DProf 19970606';
               # All values are given in HZ
               $rrun_utime=2; $rrun_stime=0; $rrun_rtime=7
               PART2
               + 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



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ext::Devel-DProf:PerloProgrammers Refeext::Devel-DProf::DProf(3p)


               - 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:

               #fOrTyTwO
               $hz=10000;
               $XS_VERSION='DProf 19971213';
               # All values are given in HZ
               $over_utime=5917; $over_stime=0; $over_rtime=5917;
               $over_tests=10000;
               $rrun_utime=1284; $rrun_stime=0; $rrun_rtime=1284;
               $total_marks=6;

               PART2
               @ 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




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ext::Devel-DProf:PerloProgrammers Refeext::Devel-DProf::DProf(3p)


       (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 subroutine.

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

       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.

AUTOLOAD
       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.

ENVIRONMENT
       "PERL_DPROF_BUFFER" sets size of output buffer in words.
       Defaults to 2**14.

       "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" macro.



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ext::Devel-DProf:PerloProgrammers Refeext::Devel-DProf::DProf(3p)


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

BUGS
       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 it).

       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: {
            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 <perl5-porters@perl.org>.

SEE ALSO
       perl, dprofpp, times(2)













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