ext::Devel::DProfPerlrProgrammers Refext::Devel::DProf::DProf(3p)NAMEDevel::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:
perl v5.8.8 2005-02-05 1
ext::Devel::DProfPerlrProgrammers Refext::Devel::DProf::DProf(3p)
#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 pro-
file 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 pro-
cess 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;
perl v5.8.8 2005-02-05 2
ext::Devel::DProfPerlrProgrammers Refext::Devel::DProf::DProf(3p)
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 previ-
ous "@" 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 over-
head 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.
perl v5.8.8 2005-02-05 3
ext::Devel::DProfPerlrProgrammers Refext::Devel::DProf::DProf(3p)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 assign-
ment 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)perl v5.8.8 2005-02-05 4
