Understanding CloudLinux resource limits in cPanel
View CPU, RAM, I/O, and process limits in cPanel Resource Usage. Understand what CloudLinux limits mean, what causes them to be hit,
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UnderHost shared hosting servers run CloudLinux OS. CloudLinux isolates each hosting account so one account's resource spikes cannot affect others. It enforces per-account limits on CPU, RAM, disk I/O, and the number of simultaneous processes.
What is CloudLinux?
On a traditional shared server, one busy website can slow down every other account on the machine. CloudLinux prevents this by putting each account in an isolated container (LVE-Lightweight Virtual Environment). Your account gets a guaranteed slice of resources and cannot use more than its limit.
This is good for reliability-other accounts cannot impact your site. But it does mean your own site can hit its limits if traffic spikes or if a script is inefficient.
View your resource usage
- Log in to cPanel
- Go to Metrics → Resource Usage
- The page shows current and historical usage across CPU, RAM, Input/Output, Entry Processes, and Physical Memory
The graphs show usage over the last hour, day, and week. Spikes that regularly hit 100% of a limit indicate a problem that needs to be addressed.
What the limits mean
| Limit | What it controls | Effect when reached |
|---|---|---|
| CPU | Percentage of a CPU core your account can use at one time | PHP scripts slow down; pages take longer to load |
| Physical Memory (PMEM) | RAM available to your PHP processes | PHP processes are killed; 500 or 503 errors appear |
| Virtual Memory (VMEM) | Virtual address space (less commonly hit) | Processes terminate with memory errors |
| I/O | Disk read/write speed available to your account | File operations slow significantly; database queries take longer |
| Entry Processes (EP) | Number of simultaneous PHP processes | Additional requests get a 503 or "Resource limit reached" error |
| Number of Processes (NPROC) | Total processes your account can run at once | New processes cannot start; cron jobs may not run |
When you hit a limit
Symptoms of hitting a CloudLinux limit:
- Your site shows a 508 Resource Limit Reached error
- Pages return 503 Service Unavailable during traffic spikes
- WordPress or PHP pages are very slow without an obvious cause
- Cron jobs stop running
Check the Resource Usage dashboard to see which limit is being hit. If the graph shows repeated CPU or PMEM spikes hitting 100%, you have identified the cause.
How to reduce resource usage
Reducing resource consumption usually involves making your site run more efficiently:
- Enable a caching plugin (WordPress: WP Super Cache, W3 Total Cache, or LiteSpeed Cache)-cached pages do not execute PHP, dramatically reducing CPU and memory usage
- Disable unused plugins-each active plugin adds overhead to every page load
- Optimise images-large image files increase I/O on every page load; use a compression plugin
- Limit WordPress revisions-add
define('WP_POST_REVISIONS', 3);towp-config.phpto cap revision history - Check for malware-compromised sites often run scripts that consume resources without your knowledge; see Malware cleanup
- Upgrade your plan-if legitimate traffic is pushing you over limits consistently, upgrading to a higher shared hosting tier or a Cloud VPS will give you more headroom
Related: Disk and bandwidth usage in cPanel: find storage and traffic problems | WordPress performance optimization | Understanding shared hosting resource limits | What is CloudLinux and how does it protect shared hosting? | How to upgrade or downgrade your hosting account
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