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Profilers, profiles and profiling

Written by Wilco Jansen Saturday, 03 April 2010 14:22

Joomla profiling

Joomla has an internal profile mechanism. It times performance from within the code-base, and gives some information about execution timings and memory usage. Profiling can be activated in the Global Configuration -> System under Debug settings.

After enabling this setting some profiling information will be rendered in the front-end. A default installation gives the following results on my system (left out all specific queries). This gives a nice overview of the timing on my test system. Around 0.5 second to render the page, and a dazzling 13Mb of internal memory used to render the page.

**Profile Information**

Application 0.002 seconds (+0.002); 0.50 Mb (+0.50) - afterLoad
Application 0.121 seconds (+0.119); 5.12 Mb (+4.62) - afterInitialise
Application 0.154 seconds (+0.034); 6.88 Mb (+1.76) - afterRoute
Application 0.469 seconds (+0.315); 11.38 Mb (+4.50) - afterDispatch
**Memory Usage**

12,962,136
**24 Queries Logged**

You can add your own profiling information in your extension to validate the timing and memory usage of your extension. Most of the times you do this after you have almost finalized your extension and want to do a final piece of quality assurance. But if you want to validate the bahaviour of your code in more detail, PHP offers you some real professional tools to profile your application. Let us take a look on this.

PHP profiling

When you develop for PHP there are a truckload of free tools available to help you improve the quality of your code as I already explained in the continuous integration building blocks blog-post from past year. When you write unit tests and enabled XDebug, you will not only have the testing results available. XDebug can do a lot more then only helping you with debugging, or generating code coverage reports, it also provides you with the opportunity to profile you code.

When you have XDebug installed, you need to set it up for generating the profile files, also referred to as cachegrind files. I use the following settings in my php.ini file to generate these cachegrind files:

; Profiling
xdebug.profiler_append=0
xdebug.profiler_enable=1
xdebug.profiler_enable_trigger=0
xdebug.profiler_output_dir=/tmp
;xdebug.profiler_output_name=crc32

See the documentation setting of XDebug to understand the meaning of these settings. Make sure to restart Apache to apply the settings. From then on there will be files with the following pattern "cachegrind.out.xxxxxx" where the xxxxxx refers to the process id of the http request. Make sure the volume has enough space, since these files can be very big on a CMS like Joomla.

The generated cachegrind files can be analysed using KCacheGrind (Linux) or Webgrind (Windows). I have found the Linux tools to be easier to install and more complete, but it is of course up to you what to use. KCachegrind can generate hierarchical overviews that give absolute, but also percentage of total use within the run. When you have setup Xdebug properly, you can drill even down on the execution flow, up till the source-code. This actually enables you to determine potential code that can be improved.

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