1Devel::SmallProf(3) User Contributed Perl Documentation Devel::SmallProf(3)
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6 Devel::SmallProf - per-line Perl profiler
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9 perl5 -d:SmallProf test.pl
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12 The Devel::SmallProf profiler is focused on the time taken for a
13 program run on a line-by-line basis. It is intended to be as "small"
14 in terms of impact on the speed and memory usage of the profiled
15 program as possible and also in terms of being simple to use. Those
16 statistics are placed in the file smallprof.out in the following
17 format:
18 <num> <time> <ctime> <line>:<text>
20 where <num> is the number of times that the line was executed, <time>
22 is the amount of "wall time" (time according the the clock on the wall
23 vs. cpu time) spent executing it, <ctime> is the amount of cpu time
24 expended on it and <line> and <text> are the line number and the actual
25 text of the executed line (read from the file).
26 The package uses the debugging hooks in Perl and thus needs the -d
28 switch, so to profile test.pl, use the command:
29 perl5 -d:SmallProf test.pl
31 Once the script is done, the statistics in smallprof.out can be sorted
33 to show which lines took the most time. The output can be sorted to
34 find which lines take the longest, either with the sort command:
35 sort -k 2nr,2 smallprof.out | less
37 or a perl script:
39 open(PROF,"smallprof.out");
41 @sorted = sort {(split(/\s+/,$b))[2] <=>
42 (split(/\s+/,$a))[2]} <PROF>;
43 close PROF;
44 print join('',@sorted);
45
47 • The "wall time" readings come from Time::HiRes and are reasonably
48 useful, at least on my system. The cpu times come from the 'times'
49 built-in and the granularity is not necessarily as small as with
50 the wall time. On some systems this column may be useful. On
51 others it may not.
52 • SmallProf does attempt to make up for its shortcomings by
54 subtracting a small amount from each timing (null time
55 compensation). This should help somewhat with the accuracy.
56 • SmallProf depends on the Time::HiRes package to do its timings. It
58 claims to require version 1.20, but may work with earlier versions,
59 depending on your platform.
60
62 SmallProf has 4 variables which can be used during your script to
63 affect what gets profiled.
64 $DB::drop_zeros (z)
66 If you do not wish to see lines which were never called, set the
67 variable "$DB::drop_zeros = 1". With "drop_zeros" set, SmallProf
68 can be used for basic coverage analysis.
69 $DB::profile (p)
71 To turn off profiling for a time, insert a "$DB::profile = 0" into
72 your code (profiling may be turned back on with "$DB::profile =
73 1"). All of the time between profiling being turned off and back
74 on again will be lumped together and reported on the "$DB::profile
75 = 0" line. This can be used to summarize a subroutine call or a
76 chunk of code.
77 %DB::packages
79 To only profile code in a certain package, set the %DB::packages
80 array. For example, to see only the code in packages "main" and
81 "Test1", do this:
82 %DB::packages = ( 'main' => 1, 'Test1' => 1 );
84 $DB::grep_format (g)
86 Generates output on a format similar to grep easily parseable from
87 tools like Emacs (see below).
88 grep format output appears as:
90 file name : line num : count : time : ctime : source
92 or
94 file name : line num : count : time : ctime : (eval n: line num) source
96 for code inside evals.
98 Times appear in miliseconds.
100 These variables can be put in a file called .smallprof in the current
102 directory. For example, a .smallprof containing
103 $DB::drop_zeros = 1;
105 $DB::profile = 0;
106 will set SmallProf to not report lines which are never touched for any
108 file profiled in that directory and will set profiling off initially
109 (presumably to be turned on only for a small portion of code).
110 Environment variable "SMALLPROF_CONFIG" can be also used to set those
112 flags, i.e:
113 SMALLPROF_CONFIG=zg perl -d:SmallProf my_script.plx
115 activates "drop_zeros" and "grep_format" modes.
117
119 Just the usual
120 perl Makefile.PL
122 make
123 make test
124 make install
125 and should install fine via the CPAN module.
127
129 Subroutine calls are currently not under the control of %DB::packages.
130 This should not be a great inconvenience in general.
131 The handling of evals is bad news. This is due to Perl's handling of
133 evals under the -d flag. For certain evals, caller() returns '(eval
134 n)' for the filename and for others it doesn't. For some of those
135 which it does, the array "@{'_<filename'}" contains the code of the
136 eval. For others it doesn't. Sometime, when I've an extra tuit or
137 two, I'll figure out why and how I can compensate for this. (Note:
138 5.6.0 made some debugging changes. This may now be fixed, I'm not
139 sure).
140 SmallProf must be invoked from the command line. If it is included on
142 the shebang line, the file in which it is included will not be visible
143 in the symbol table. Profiling will continue as expected, but the
144 contents of the source lines will not be listed. This is new as of
145 5.6.0.
146 Comments, advice and questions are welcome. If you see inefficent
148 stuff in this module and have a better way, please let me know.
149
151 1. Use the "DB::grep_format" flag to turn on grep like format, i.e.
152 SMALLPROF_CONFIG=g perl -d:SmallProf myscript.pl
154 2. Tell Emacs/XEmacs to read smallprof.out as grep output:
156 M-x grep RET C-a C-k cat smallprof.out RET
158 3. Point and click to go to the script hot spots!
160
162 Devel::SmallProf was developed by Ted Ashton <ashted@cpan.org>. It is
163 currently being maintained by Salvador Fandiño <sfandino@yahoo.com>.
164 SmallProf was developed from code originally posted to usenet by
166 Philippe Verdret <philippe.verdret@sonovision-itep.fr>. Special thanks
167 to Geoffrey Broadwell <habusan2@sprynet.com> for his assistance on the
168 Win32 platform and to Philippe for his patient assistance in testing
169 and debugging.
170
172 Copyright (c) 1997-2000 Ted Ashton
173 Copyright (c) 2003-2007 Salvador Fandiño
175 This module is free software and can be redistributed and/or modified
177 under the same terms as Perl itself.
178
180 Devel::FastProf is a simplified and much faster version of this module.
181 Devel::DProf, Time::HiRes.
183
185 Hey! The above document had some coding errors, which are explained
186 below:
187 Around line 384:
189 Non-ASCII character seen before =encoding in 'Fandiño'. Assuming
190 CP1252
191perl v5.36.0 2023-01-20 Devel::SmallProf(3)