High CPU usage
If you are experiencing high CPU usage on your site, there are a few possible ways WP Rocket could cause this:
Pages are not cached
Make sure that WP Rocket is active and caches your pages:
How to check if WP Rocket is caching your pages
Preload and Remove Unused CSS
If you or your host notices too many requests related to WP Rocket in your server logs, you can check the User Agent to find the source of the problematic ones:
WP Rocket/Preloadindicates PreloadWP-Rocket/SaaSindicates Remove Unused CSS
In either case you can install this helper plugin which modifies both of them at once:
📥 Download (.zip): WP Rocket | Change Parameters
Developers: You can find the code for this plugin on GitHub.
The next time the Preload and Used CSS generation run, the above helper will change the parameters as follows:
- Changes the limits of the preloading batch like this:
- Maximum number of URLs decreases from 45 to 25 URLs.
- Minimum number of URLs decreases from 5 to 3 URLs.
- Increase the waiting time between preloading batches, from 60 seconds to 120 seconds.
- Increase the waiting time between preload requests, from 0.5 seconds to 1 second.
- Reduce the batch of maximum URLs to generate the Used CSS for, from 100 URLs to 25 URLs.
- Increase the waiting time between Used CSS generation batches, from 60 seconds to 120 seconds.
When using this helper plugin, both options are limited at the same time because, in most cases, the Preload speed defines the Used CSS generation speed (as per this). And, limiting the Used CSS generation speed as such acts as guard too.
Therefore, this plugin is the solution for sites that need to keep using the Preload and Remove Unused CSS features, but without affecting the CPU and resources usage of their server.
Limit Preload to your site's most visited pages
In some cases, it’s more efficient to focus the preload process on your most visited pages. This can be useful for large websites with limited server resources, where preloading all URLs causes high CPU usage. This also gives you more control over specific pages to preload.
In this case, you can install the Smart Preload Helper:
📥 Download (.zip): WP Rocket | Smart Preload
Developers: You can find the code for this plugin on GitHub.
Important! Using this helper will introduce a major modification to the default Preload feature. This approach doesn't have known issues so far. Also, further customization beyond the current functionality is not available.
This helper works automatically to monitor the number of page views to each of your site's pages and only Preloads the most visited pages.
You can set the limit for the maximum number of pages to be preloaded and also specify specific pages that should be preloaded in the settings page that it creates:
Note: While the Smart Preload Helper will automatically monitor your site, analyzing the traffic on your site doesn't take effect immediately. So please allow some time for the tool to analyze each page to see the full results.
LazyLoad for CSS background images
The LazyLoad for CSS background images feature has to process all the CSS of your pages.
Therefore, this feature can cause problems to the CPU usage if the site has a lot of CSS or the server doesn't have enough resources. The more CSS the site has, the higher the impact this can have on the CPU usage.
Unfortunately, there's no available workaround. So, if you're having this problem when using this feature, you'd need to keep it deactivated.
Excessive cache clearing
Sometimes, you might notice the cache is being cleared randomly, without a clear explanation, and this can cause CPU issues because cached won't be available, and the requests will reach the server with more frequency.
Please check our Cache is incomplete, cleared too frequently or randomly guide for more information.
Priority Elements
If admin-ajax requests from WP Rocket's Beacon script are causing an issue, you can try disabling the Priority Elements features.
Other file optimizations
Occasionally some of the other options on the File Optimization tab, such as Minify/Combine can cause high CPU usage in cases where your site has a lot of CSS or JS files. Try disabling these options and then monitor your CPU usage to see if it helps.