Software profiling is a powerful technique when you want to optimize your code. Among other things, a profile snapshot will show you which parts of your software are the slower.
In this article I will explain how to create a profile snapshot for a PHP script.
Requirements
I assume you are using Ubuntu and you already have PHP installed. Please also install XDebug 3 and KCachegrind:
$ apt install php-xdebug
$ apt install kcachegrind
Create profile file
As an example, I will profile tests from jawira/plantuml-encoding.
$ git clone https://github.com/jawira/plantuml-encoding.git
$ cd plantuml-encoding
$ php tests/vanilla.php
Execute the following command to profile tests/vanilla.php
:
$ php -dxdebug.mode=profile -dxdebug.output_dir=. tests/vanilla.php
After the execution is finished, a new profile snapshot will be created. This profile file has the following name pattern cachegrind.out.xxxxx
(where xxxxx
is a number).
XDebug can be configured in php.ini
. Here we have configured XDebug on-the-fly passing php.ini
configuration through the terminal.
-
-dxdebug.mode=profile: This option makes
profile mode
enabled for this command. -
-dxdebug.output_dir=.: Save profile snapshots in current dir "
.
", otherwise snapshots are saved in/tmp
.
In our case profiling mode
is ephemeral, but it can be a problem if you are activating profiling by other means (for example directly editing php.ini
file). Profile snapshots can take a LOT of disk space, never leave profile mode permanently enabled.
Opening profile file
To visualize your profile snapshot, simply open the snapshot (in our case cachegrind.out.14476
) with KCachegrind.
The reading and interpretation of profiling files are beyond the scope of this article, yet I recommend you to see this video https://www.youtube.com/watch?v=h-0HpCblt3A presenting KCachegrind.
Conclusion
Creating a profile snapshot is easy if you understand how to configure XDebug properly. Using -d
options is very convenient technique to enable profiling from the terminal.
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