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21.15. Benchmarking a mod_perl Application

You have an idea to speed up your
application, but you're not sure whether your change will help.

21.15.2. Solution

Use Apache::Timeit to time how long your content handler takes to
run:

PerlModule Apache::Timeit
PerlFixupHandler Apache::Timeit

For more detailed analysis, use the Apache::DProf module available
from CPAN:

PerlModule Apache::DProf

21.15.3. Discussion

The Apache::Timeit module is available at http://perl.apache.org/dist/contrib/Timeit.pm.

This module records in the error log the amount of time that elapsed
while the content handler ran. By scanning the logs and averaging
these numbers, you can see which pages take longer to generate, and
you can then start to figure out why.

To drill down into your code and figure out which parts of the
content handler are taking the most time, use the Apache::DProf
module. This module connects the standard (as of v5.8) Devel::DProf
module to Apache and mod_perl.

The profiler records time spent in every subroutine the Perl module
executes. The record of times is written to a file named
dprof/$$/tmon.out
($$ is the process ID of the Apache child
process), located under the ServerRoot directory. This file
corresponds to every Perl subroutine encountered during the lifetime
of the Apache child process. To profile just a single request, set
the MaxRequestsPerChild directive in the
httpd.conf file:

MaxRequestsPerChild 1

You must create and chmod this directory yourself:

cd $APACHE_SERVER_ROOT
mkdir logs/dprof
chmod 777 logs/dprof

To analyze the output, use the dprofpp program:

dprofpp -r dprof/13169/tmon.out
Total Elapsed Time = 89.93962 Seconds
Real Time = 89.93962 Seconds
Exclusive Times
%Time ExclSec CumulS #Calls sec/call Csec/c Name
0.01 0.010 0.010 1 0.0100 0.0100 Apache::Reload::handler
0.00 0.000 -0.000 1 0.0000 - Apache::DProf::handler
0.00 0.000 -0.000 1 0.0000 - MP002::trans
0.00 0.000 -0.000 1 0.0000 - MP002::fixup
0.00 0.000 -0.000 1 0.0000 - MP002::content

The -r option makes
dprofpp display elapsed time instead of the
default CPU time. The difference is important for mod_perl
applications, where I/O and other non-CPU tasks are often significant
causes of user-perceived delay.

There are a lot of options to dprofpp that
refine and manipulate timing data. For example, -R gives separate timing data for each
anonymous subroutine in a package, rather than lumping them together;
-l sorts by the number of times the
subroutine was called, rather than how long it took. See the
dprofpp manpage for a complete list.

21.15.4. See Also

Recipe 9.12 in mod_perl Developer's Cookbook;
documentation for the CPAN module Apache::DProf; documentation for
the standard module Devel::DProf; the dprofpp(1)
manpage; the section "The Perl Profiler" in Chapter 20 of
Programming Perl

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21.14. Reloading Changed Modules		21.16. Templating with HTML::Mason

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