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Devel::DProf(3pm)		 Perl Programmers Reference Guide		Devel::DProf(3pm)

       Devel::DProf - a Perl code profiler

	       perl5 -d:DProf test.pl

       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 pro-
       filer uses the debugging hooks.	So to profile script test.pl the following command should
       be used:

	       perl5 -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:


       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 pro-
       filer These values are used by the profiler to subtract the overhead from the runtimes.

       The lines starting with "@" mark time passed from the previous "@" line.  The lines start-
       ing with "&" introduce new subroutine id and show the package and the subroutine name of
       this id.  Lines starting with "+", "-" and "*" mark entering and exit of subroutines by
       ids, and "goto &subr".

       The old-style "+"- and "-"-lines are used to mark the overhead related to writing to pro-
       filer-output file.

       When Devel::DProf finds a call to an &AUTOLOAD subroutine it looks at the $AUTOLOAD vari-
       able 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 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.

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

       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).

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

       perl, dprofpp, times(2)

perl v5.8.0				    2002-06-01				Devel::DProf(3pm)
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