Profilers identify bottlenecks in Perl programs
Not Without Side Effects
Just like any other profiler, Devel::NYTProf also involves some overhead that can completely falsify the measured results in some cases. The profiler's activities are particularly invasive if a program is not waiting for external events, such as network traffic or disk access, which are magnitudes of scale slower.
For a program running at full CPU speed, the run time can be 10 times longer if you enable the profiler.
Figure 7 shows the effect the NYT profiler has on the short l4ptest test program (Listing 4). The program configures Log4perl for the $INFO logging priority and then issues $DEBUG messages, which should be suppressed because of their lower priority. Log4perl has optimized this case; after all, a disabled logging system shouldn't have any measurable effect.
Listing 4
l4ptest
#!/usr/local/bin/perl -w
use strict;
use Log::Log4perl qw(:easy);
Log::Log4perl->easy_init($INFO);
for(1..100_000) {
DEBUG "waah!";
}
The script running without the profiler achieves around 100,000 calls in about 100msec; the script run time is about 10 times longer with NYTProf enabled.
This by no means detracts from the quality of the profiler, but it is important to take this into consideration when measuring script run time and interpreting the results.
The module also is quite at home in the Apache server's mod_perl. Adding PerlModule Devel::NYTProf::Apache to the configuration loads the module and tells it to append profile data to the /tmp/nytprof.$$.out file for incoming requests, where $$ represents the PID for the Apache process handling the request.
Calling nytprofhtml again creates a collection of web pages for in-depth analysis of the web application's performance that could very well point you to critical code sections that need improvement.
Infos
- Listings for this article: http://www.linux-magazine.com/resources/article_code
- Amazon Web Services (developer token application): http://amazon.com/soap
- Devel::NYTProf: http://search.cpan.org/dist/Devel-NYTProf/
- Tim Bunce blog "NYTProf v2 – the background story," http://blog.timbunce.org/2008/07/16/nytprof-v2-the-background-story/
- Tim Bunce at OSCON 2008: http://en.oreilly.com/oscon2008/public/schedule/speaker/6816
The Author
Michael Schilli works as a software engineer with Yahoo! in Sunnyvale, California. He is the author of Goto Perl 5 (German) and Perl Power (English), both published by Addison-Wesley, and he can be contacted at mailto:mschilli@perlmeister.com. Michael's homepage is at http://perlmeister.com.
« Previous 1 2 3
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
US / Canada
UK / Australia
Subscribe to our Linux newsletters
News
-
Alpine Linux 3.17 Now Available to the General Public
The developers of Alpine Linux have officially announced the release of the latest version of the security-focused Linux distribution.
-
The New StarFighter Linux Laptop Now Available for Preorder
A new, completely customizable Linux laptop is now available to preorder from Star Labs.
-
Critical Escalation Vulnerability Found in the Linux Kernel
A new local privilege escalation vulnerability has been discovered in the Linux kernel and users are encouraged to upgrade/patch immediately.
-
AlmaLinux 8.7 Now Available
The developers of AlmaLinux have released the latest version of the OS, named Stone Smilodon, to the general public.
-
New Arch-Based Linux Distribution Aims to be Beginner-Friendly
CachyOS has been created to serve as a Linux distribution for everyone, even while being based on the more complex Arch Linux.
-
elementary OS 7 Getting Closer to Release
The team behind elementary OS has announced they are now focused on putting the finishing touches on the next major release of the Linux distribution.
-
Nitrux 2.5 Released with Kernel 6.0 and KDE Plasma 5.26
Nitrux 2.5 has been officially released and is the first systemd-free distribution to include both kernel 6.0 and KDE Plasma 5.26.
-
Zorin OS 16.02 Now Available
Zorin OS 16.2 has been officially released just seven months after the first point release of the user-friendly Linux operating system.
-
Linus Torvalds Considers Dropping i486 Support
In a message to the Linux kernel mailing list, creator Linus Torvalds indicates that it's time to jettison support for i486 machines in with Linux kernel.
-
Firefox 106 Lands with Back-Forward Swipe Gesture Support
The latest release of Firefox is out, and it adds two important new features to the open source browser.