Profilers identify bottlenecks in Perl programs
Run-Time Speed

© Dominic Ziegler, Fotolia
Instead of souped up CPUs, simple programming tricks are often all it takes to speed up a program. Profilers can discover bottlenecks that need more TLC from the developer.
If you don't spend all day playing video games, you will be quite happy without the latest and greatest CPU, and you can save money on hardware while saving power and reducing your personal CO² footprint.
But what happens if a Perl program does not perform as well as you would like? As a first step, you might be able to accelerate the program with very little effort by optimizing the code at neuralgic points.
In most cases, just one or two targeted improvements will help you achieve 90 percent of the total optimization potential. The remaining 10 percent are more likely to involve wide-ranging, architectural changes that take 10 times as long to implement and make the resulting program so difficult to maintain that more experienced developers are likely to turn down the option.
Profilers are programs that discover bottlenecks, or hotspots. They show you where the program spends most of its time and help to optimize these crucial sections in a targeted way.
Perl has many tools of this kind. For example, if a module uses the Log4perl logging framework, it is simple to display the number of milliseconds (msec) that elapse along with the log messages, thus creating a timescale.
Finding Bottlenecks
The simple test script amzntest (Listing 1) uses the CPAN Net::Amazon module to retrieve book details from the Amazon Web API (assuming you enter a valid token, which you can get from Amazon Web Services [2]).
Listing 1
amzntest
A request takes about a second, but what does the script use this time for – picking up the data or the analyzing the XML response? Adding
use Log::Log4perl; Log::Log4perl->init("timer.l4p");
to the script header enables the Log4perl statements embedded in Net::Amazon by loading the timer.l4p configuration file. This outputs the date (%d) and the number of milliseconds since the program started (%r) for each message it logs. The logging level is set to DEBUG and is thus fairly verbose.
To cut down on lengthy log messages, the configuration file in Listing 2 uses the abbreviation %S to define a so-called Custom Cspec. This appears in the layout, instead of the more typical %m (for the log message).
The associated Perl subroutine returns a shorter, 25-character message to the screen appender. The layout closes with a platform-dependent newline character defined by %n.
Listing 2
timer.l4p
Quick Fix
Figure 1 shows that Net::Amazon sends a web request to Amazon 79msec after the program launches; however, the XML parser does not start working until 739msec have elapsed. Thus, the web request takes 75 percent of the 800msec required by the script.

As you will agree, it makes sense to use a web cache for frequently retrieved ASIN numbers, and Net::Amazon enables this if we ask it to (see Listing 3). This really does reduce the script run time, which drops to 180msec for repetitions (see Figure 2) with the use of File::Cache as a persistent cache.

Listing 3
Web Cache
Quick Results
Now you might argue that tricks of this kind aren't always going to help, but the decisive issue here is that five lines of code and a minute spent thinking about options achieved a speed boost of 400 percent.
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you've found an article to be beneficial.
News
-
Fedora 39 Beta is Now Available for Testing
For fans and users of Fedora Linux, the first beta of release 39 is now available, which is a minor upgrade but does include GNOME 45.
-
Fedora Linux 40 to Drop X11 for KDE Plasma
When Fedora 40 arrives in 2024, there will be a few big changes coming, especially for the KDE Plasma option.
-
Real-Time Ubuntu Available in AWS Marketplace
Anyone looking for a Linux distribution for real-time processing could do a whole lot worse than Real-Time Ubuntu.
-
KSMBD Finally Reaches a Stable State
For those who've been looking forward to the first release of KSMBD, after two years it's no longer considered experimental.
-
Nitrux 3.0.0 Has Been Released
The latest version of Nitrux brings plenty of innovation and fresh apps to the table.
-
Linux From Scratch 12.0 Now Available
If you're looking to roll your own Linux distribution, the latest version of Linux From Scratch is now available with plenty of updates.
-
Linux Kernel 6.5 Has Been Released
The newest Linux kernel, version 6.5, now includes initial support for two very exciting features.
-
UbuntuDDE 23.04 Now Available
A new version of the UbuntuDDE remix has finally arrived with all the updates from the Deepin desktop and everything that comes with the Ubuntu 23.04 base.
-
Star Labs Reveals a New Surface-Like Linux Tablet
If you've ever wanted a tablet that rivals the MS Surface, you're in luck as Star Labs has created such a device.
-
SUSE Going Private (Again)
The company behind SUSE Linux Enterprise, Rancher, and NeuVector recently announced that Marcel LUX III SARL (Marcel), its majority shareholder, intends to delist it from the Frankfurt Stock Exchange by way of a merger.