1. Remove any unwanted plugins.
Sometimes users did kept the old plugins by just deactivating them which this process can cause issue on the usage or CPU/Virtual Memory usage.
2. Update plugins to the latest version available.
The plugins involve will required updates to fixed their bug or any problem which may lead to further complication on the plugins itself that may lead to other related problem mostly on the CPU/Virtual Memory usage.
3. Routine database tables optimization.
To keep things running smoothly, you need to log onto PhpMyAdmin on a routine bases and optimize the database tables. Unoptimized data tables can overload the server. More over, the CPU usage is also more for reading unoptimized data tables. Besides data table optimization, you can also delete spam/unapproved data.
4. Themes usage and compatibility.
This is the most common reason or causes on the CPU/Virtual Memory limit hit problems. Before proceed to install a theme, the best is to check on its compatibility and requirement which normally some fancy themes required more resources to operate normally.
5. WordPress upgrading and caching.
Are you still laid behind with the older WordPress version? Well, if that is so then it is high time you upgrade to an advanced and latest version. Most of us ignore the idea of upgrading wordpress just because it works perfectly. An upgradation helps because the newer versions are better in terms of security and optimization.
You may also install wordpress caching program. Caching archives each web page on your site. This lowers server load as it doesn’t require sending multiple queries to the database for generating multiple pages.
6. Reduce widgets usage.
In certain WordPress run by user may contain some unnecessary widgets which normally leads to complication to whereby more usag on the CPU/Virtual Memory is required to operate.
7. Lower PHP or Database calls.
PHP scripts and database calls also consume a lot of CPU resource. Caching your sites helps but certain database/PHP calls cannot be avoided. Hence, you should go through the plugins documentation carefully and disable the unnecessary options.
8. Lower the load on index.php file.
At peak hours, your homepage may create a load on your server during the peak hours. To lower this load, ensure keeping your homepage simple. Try to lower the number of posts on your homepage and remove unwanted files, links and high resolution images. It would be even better if you choose a CDN service like Cloudfront
9. Disable WP-Cron.
Disable WP-Cron or change to a scheduled task to run every hour. This will greatly reduce your CPU usage. WP-Cron manages all your scheduled events so it is continuaally active on many sites when it isn’t necesssary.
10 Avoid plugins that use excessive CPU load.
These are often backup and security pluggins. These functions are best being offered by a quality host provider that has integrated solutions.