1Devel::DProf(3pm) Perl Programmers Reference Guide Devel::DProf(3pm)
2
6 Devel::DProf - a Perl code profiler
7
9 perl -d:DProf test.pl
10
12 The Devel::DProf package is a Perl code profiler. This will collect
13 information on the execution time of a Perl script and of the subs in
14 that script. This information can be used to determine which
15 subroutines are using the most time and which subroutines are being
16 called most often. This information can also be used to create an
17 execution graph of the script, showing subroutine relationships.
18 To profile a Perl script run the perl interpreter with the -d debugging
20 switch. The profiler uses the debugging hooks. So to profile script
21 test.pl the following command should be used:
22 perl -d:DProf test.pl
24 When the script terminates (or when the output buffer is filled) the
26 profiler will dump the profile information to a file called tmon.out.
27 A tool like dprofpp can be used to interpret the information which is
28 in that profile. The following command will print the top 15
29 subroutines which used the most time:
30 dprofpp
32 To print an execution graph of the subroutines in the script use the
34 following command:
35 dprofpp -T
37 Consult dprofpp for other options.
39
41 The old profile is a text file which looks like this:
42 #fOrTyTwO
44 $hz=100;
45 $XS_VERSION='DProf 19970606';
46 # All values are given in HZ
47 $rrun_utime=2; $rrun_stime=0; $rrun_rtime=7
48 PART2
49 + 26 28 566822884 DynaLoader::import
50 - 26 28 566822884 DynaLoader::import
51 + 27 28 566822885 main::bar
52 - 27 28 566822886 main::bar
53 + 27 28 566822886 main::baz
54 + 27 28 566822887 main::bar
55 - 27 28 566822888 main::bar
56 [....]
57 The first line is the magic number. The second line is the hertz
59 value, or clock ticks, of the machine where the profile was collected.
60 The third line is the name and version identifier of the tool which
61 created the profile. The fourth line is a comment. The fifth line
62 contains three variables holding the user time, system time, and
63 realtime of the process while it was being profiled. The sixth line
64 indicates the beginning of the sub entry/exit profile section.
65 The columns in PART2 are:
67 sub entry(+)/exit(-) mark
69 app's user time at sub entry/exit mark, in ticks
70 app's system time at sub entry/exit mark, in ticks
71 app's realtime at sub entry/exit mark, in ticks
72 fully-qualified sub name, when possible
73 With newer perls another format is used, which may look like this:
75 #fOrTyTwO
77 $hz=10000;
78 $XS_VERSION='DProf 19971213';
79 # All values are given in HZ
80 $over_utime=5917; $over_stime=0; $over_rtime=5917;
81 $over_tests=10000;
82 $rrun_utime=1284; $rrun_stime=0; $rrun_rtime=1284;
83 $total_marks=6;
84 PART2
86 @ 406 0 406
87 & 2 main bar
88 + 2
89 @ 456 0 456
90 - 2
91 @ 1 0 1
92 & 3 main baz
93 + 3
94 @ 141 0 141
95 + 2
96 @ 141 0 141
97 - 2
98 @ 1 0 1
99 & 4 main foo
100 + 4
101 @ 142 0 142
102 + & Devel::DProf::write
103 @ 5 0 5
104 - & Devel::DProf::write
105 (with high value of $ENV{PERL_DPROF_TICKS}).
107 New "$over_*" values show the measured overhead of making $over_tests
109 calls to the profiler These values are used by the profiler to subtract
110 the overhead from the runtimes.
111 Lines starting with "@" mark the amount of time passed since the
113 previous "@" line. The numbers following the "@" are integer tick
114 counts representing user, system, and real time. Divide these numbers
115 by the $hz value in the header to get seconds.
116 Lines starting with "&" map subroutine identifiers (an integer) to
118 subroutine packages and names. These should only occur once per
119 subroutine.
120 Lines starting with "+" or "-" mark normal entering and exit of
122 subroutines. The number following is a reference to a subroutine
123 identifier.
124 Lines starting with "*" mark where subroutines are entered by "goto
126 &subr", but note that the return will still be marked as coming from
127 the original sub. The sequence might look like this:
128 + 5
130 * 6
131 - 5
132 Lines starting with "/" is like "-" but mark where subroutines are
134 exited by dying. Example:
135 + 5
137 + 6
138 / 6
139 / 5
140 Finally you might find "@" time stamp marks surrounded by "+ &
142 Devel::DProf::write" and "- & Devel::DProf::write" lines. These 3
143 lines are outputted when printing of the mark above actually consumed
144 measurable time.
145
147 When Devel::DProf finds a call to an &AUTOLOAD subroutine it looks at
148 the $AUTOLOAD variable to find the real name of the sub being called.
149 See "Autoloading" in perlsub.
150
152 "PERL_DPROF_BUFFER" sets size of output buffer in words. Defaults to
153 2**14.
154 "PERL_DPROF_TICKS" sets number of ticks per second on some systems
156 where a replacement for times() is used. Defaults to the value of "HZ"
157 macro.
158 "PERL_DPROF_OUT_FILE_NAME" sets the name of the output file. If not
160 set, defaults to tmon.out.
161
163 Builtin functions cannot be measured by Devel::DProf.
164 With a newer Perl DProf relies on the fact that the numeric slot of
166 $DB::sub contains an address of a subroutine. Excessive manipulation
167 of this variable may overwrite this slot, as in
168 $DB::sub = 'current_sub';
170 ...
171 $addr = $DB::sub + 0;
172 will set this numeric slot to numeric value of the string
174 "current_sub", i.e., to 0. This will cause a segfault on the exit from
175 this subroutine. Note that the first assignment above does not change
176 the numeric slot (it will mark it as invalid, but will not write over
177 it).
178 Another problem is that if a subroutine exits using goto(LABEL),
180 last(LABEL) or next(LABEL) then perl may crash or Devel::DProf will die
181 with the error:
182 panic: Devel::DProf inconsistent subroutine return
184 For example, this code will break under Devel::DProf:
186 sub foo {
188 last FOO;
189 }
190 FOO: {
191 foo();
192 }
193 A pattern like this is used by Test::More's skip() function, for
195 example. See perldiag for more details.
196 Mail bug reports and feature requests to the perl5-porters mailing list
198 at <perl5-porters@perl.org>.
199
201 perl, dprofpp, times(2)
202perl v5.10.1 2009-04-14 Devel::DProf(3pm)