Joomla is a popular CMS that is highly extensible and customizable. Here are some steps to optimize your Joomla installation, and reduce the CPU consumption of this script.
This is probably the most important. You can lower the footprint of your site on the server noticibly by enabling caching. This should be enabled at all times.
Change your template
Some templates may look nice, but they can use up to 70 images per page request, each of which generates an HTTP connection to the server. When many people visit your site, you will end up consuming enough CPU to cause the server’s load to rise. You should consider clean template styles instead of image heavy templates.
Disable Gzip compression
The CPU has to work harder to compress each of your pages before it sends it out. If you have Gzip compression enabled, an extra overhead is added to each page request.
Be careful about components
Many components are heavy CPU consumers, and will cause your site to raise the server’s load. Make sure you’re only using the minimum amount of components that are necessary to the operation of your site.
Do not use statistics components
These use a lot of SQL queries to constantly update and display your site statistics. Use Awstats or Google Analytics to track users.
If you are using a forum bridge/extension such as FireBoard or something similar, make sure to require visitors to register before they are allowed to search and post, and employ captchas for your board.
These steps are not guaranteed fixes to bring a site to normal CPU consumption, but they will drastically reduce the amount of CPU consumed by a Joomla installation. If there are any questions about this, please don’t hesitate to contact firstname.lastname@example.org