Devel::SmallProf(3) User Contributed Perl Documentation Devel::SmallProf(3)NAMEDevel::SmallProf - per-line Perl profiler
SYNOPSIS
perl5 -d:SmallProf test.pl
DESCRIPTION
The Devel::SmallProf profiler is focused on the time taken for a
program run on a line-by-line basis. It is intended to be as "small"
in terms of impact on the speed and memory usage of the profiled
program as possible and also in terms of being simple to use. Those
statistics are placed in the file smallprof.out in the following
format:
<num> <time> <ctime> <line>:<text>
where <num> is the number of times that the line was executed, <time>
is the amount of "wall time" (time according the the clock on the wall
vs. cpu time) spent executing it, <ctime> is the amount of cpu time
expended on it and <line> and <text> are the line number and the actual
text of the executed line (read from the file).
The package uses the debugging hooks in Perl and thus needs the -d
switch, so to profile test.pl, use the command:
perl5 -d:SmallProf test.pl
Once the script is done, the statistics in smallprof.out can be sorted
to show which lines took the most time. The output can be sorted to
find which lines take the longest, either with the sort command:
sort -k 2nr,2 smallprof.out | less
or a perl script:
open(PROF,"smallprof.out");
@sorted = sort {(split(/\s+/,$b))[2] <=>
(split(/\s+/,$a))[2]} <PROF>;
close PROF;
print join('',@sorted);
NOTES
· The "wall time" readings come from Time::HiRes and are reasonably
useful, at least on my system. The cpu times come from the 'times'
built-in and the granularity is not necessarily as small as with
the wall time. On some systems this column may be useful. On
others it may not.
· SmallProf does attempt to make up for its shortcomings by
subtracting a small amount from each timing (null time
compensation). This should help somewhat with the accuracy.
· SmallProf depends on the Time::HiRes package to do its timings. It
claims to require version 1.20, but may work with earlier versions,
depending on your platform.
OPTIONS
SmallProf has 4 variables which can be used during your script to
affect what gets profiled.
$DB::drop_zeros (z)
If you do not wish to see lines which were never called, set the
variable "$DB::drop_zeros = 1". With "drop_zeros" set, SmallProf
can be used for basic coverage analysis.
$DB::profile (p)
To turn off profiling for a time, insert a "$DB::profile = 0" into
your code (profiling may be turned back on with "$DB::profile =
1"). All of the time between profiling being turned off and back
on again will be lumped together and reported on the "$DB::profile
= 0" line. This can be used to summarize a subroutine call or a
chunk of code.
%DB::packages
To only profile code in a certain package, set the %DB::packages
array. For example, to see only the code in packages "main" and
"Test1", do this:
%DB::packages = ( 'main' => 1, 'Test1' => 1 );
$DB::grep_format (g)
Generates output on a format similar to grep easily parseable from
tools like Emacs (see below).
grep format output appears as:
file name : line num : count : time : ctime : source
or
file name : line num : count : time : ctime : (eval n: line num) source
for code inside evals.
Times appear in miliseconds.
These variables can be put in a file called .smallprof in the current
directory. For example, a .smallprof containing
$DB::drop_zeros = 1;
$DB::profile = 0;
will set SmallProf to not report lines which are never touched for any
file profiled in that directory and will set profiling off initially
(presumably to be turned on only for a small portion of code).
Environment variable "SMALLPROF_CONFIG" can be also used to set those
flags, i.e:
SMALLPROF_CONFIG=zg perl -d:SmallProf my_script.plx
activates "drop_zeros" and "grep_format" modes.
INSTALLATION
Just the usual
perl Makefile.PL
make
make test
make install
and should install fine via the CPAN module.
BUGS
Subroutine calls are currently not under the control of %DB::packages.
This should not be a great inconvenience in general.
The handling of evals is bad news. This is due to Perl's handling of
evals under the -d flag. For certain evals, caller() returns '(eval
n)' for the filename and for others it doesn't. For some of those
which it does, the array "@{'_<filename'}" contains the code of the
eval. For others it doesn't. Sometime, when I've an extra tuit or
two, I'll figure out why and how I can compensate for this. (Note:
5.6.0 made some debugging changes. This may now be fixed, I'm not
sure).
SmallProf must be invoked from the command line. If it is included on
the shebang line, the file in which it is included will not be visible
in the symbol table. Profiling will continue as expected, but the
contents of the source lines will not be listed. This is new as of
5.6.0.
Comments, advice and questions are welcome. If you see inefficent
stuff in this module and have a better way, please let me know.
EMACS/XEMACS HACK
1. Use the "DB::grep_format" flag to turn on grep like format, i.e.
SMALLPROF_CONFIG=g perl -d:SmallProf myscript.pl
2. Tell Emacs/XEmacs to read smallprof.out as grep output:
M-x grep RET C-a C-k cat smallprof.out RET
3. Point and click to go to the script hot spots!
AUTHORDevel::SmallProf was developed by Ted Ashton <ashted@cpan.org>. It is
currently being maintained by Salvador Fandin~o <sfandino@yahoo.com>.
SmallProf was developed from code originally posted to usenet by
Philippe Verdret <philippe.verdret@sonovision-itep.fr>. Special thanks
to Geoffrey Broadwell <habusan2@sprynet.com> for his assistance on the
Win32 platform and to Philippe for his patient assistance in testing
and debugging.
COPYRIGHT AND LICENSE
Copyright (c) 1997-2000 Ted Ashton
Copyright (c) 2003-2007 Salvador Fandin~o
This module is free software and can be redistributed and/or modified
under the same terms as Perl itself.
SEE ALSO
Devel::FastProf is a simplified and much faster version of this module.
Devel::DProf, Time::HiRes.
perl v5.14.0 2007-05-11 Devel::SmallProf(3)
