Index for Section 3

Alphabetical listing for D

Bottom of page

Devel::DProf(3)
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
	  - 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

  (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.

  The lines starting with "@" mark time passed from the previous "@" line.
  The lines starting 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 profiler-output file.

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.

  "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)

Index for Section 3

Alphabetical listing for D

Top of page