Tuning server parameters¶
If you are looking for methods to improve the performance of AtoM and your deployment, you are now in the right place!
First of all, most common performance issues could be solved by redesigning the code, and that’s something that we are working on constantly. But there’s no doubt that some configuration tweaks in your servers can give you better results.
This page describes the most common performance tweaks used in AtoM.
PHP opcode cache¶
PHP is an interpreted language. Each time a client requests a PHP page, the server will read the source code and compile it before it’s executed. APC is one of the solutions available that caches the compiled output of each PHP script in order to save CPU cycles in subsequent requests.
Deploying APC is really easy:
sudo apt-get install php-apc
We consider this component so important that it’s listed as a mandatory extension under Technical Requirements. Really, don’t ignore this: we consider compiling the same source code again and again in a per-request basis to be a huge waste of time and computing resources.
In addition, there is one particular directive in APC that you should tweak to
get the best performance: apc.stat, enabled by default, is a directive
that forces APC to check the PHP scripts on each request to determine if they
have been modified. Modifying PHP scripts may happen frequently in development
environments, but in production you don’t really need this. When you are
upgrading AtoM, just restart the PHP pool and the APC cache will be flushed.
Note
APC has not been ported to PHP 5.5. Instead, Zend has contributed their Zend Optimizer+ opcode cache (OPcache). However, user-data cache is not something that OPcache implements, so if you are planning to use PHP 5.5 please look at APCu as a valid replacement for user-land caching, which emulates its functionality while providing the same API.
Other components that can be tweaked¶
This document is work in progress. We are planning to describe more tweaking options in at least the following components:
- MySQL
- Nginx
- PHP-FPM
- Linux
- Caching proxy servers (HTTP accelerators)
- etc…