Understanding Hosting Resource Limits:CPU, RAM, Entry Processes and I/O
CPU, memory, entry processes, I/O and inode limits decide how a shared hosting account behaves under load. What each limit means, how to read your usage, and how to reduce it.
Table of Contents
On shared and cloud hosting, each account is given limits on CPU, physical memory, entry processes, total processes, disk I/O and inodes. When a site reaches one of these limits, the server slows it down or refuses extra requests, which visitors experience as slow pages or errors such as 508 Resource Limit Is Reached.
Knowing what each limit measures lets you tell whether you need optimisation or a bigger plan.
Why limits exist
Shared servers host many accounts. Without per-account limits, one busy or compromised site could use all the CPU and memory and slow every other site on the machine. Many hosts enforce limits with CloudLinux, which places each account in its own lightweight virtual environment (LVE) with a fixed resource budget. Other platforms use similar mechanisms; the names below follow the common CloudLinux terms.
The limits, one by one
| Limit | What it measures | What happens when it is reached |
|---|---|---|
| CPU (SPEED) | Share of CPU time, often as a percentage of one core (100% = one core) | Processes are slowed down; pages load slowly |
| Physical memory (PMEM) | RAM used by the account's processes | New processes fail; PHP may return 500 or 503 errors |
| Entry processes (EP) | Simultaneous connections being handled by PHP/CGI at the same moment | Extra requests are refused with a 508 error |
| Number of processes (NPROC) | All processes the account runs, including cron, SSH and mail | New processes cannot start |
| I/O (IO) | Disk read/write speed | Disk-heavy operations are slowed |
| IOPS | Number of disk operations per second | Many small file operations are slowed |
| Inodes | Number of files and folders | You cannot create files, upload media or receive email |
Entry processes are not visitors
An entry process is a request being processed by PHP right now. If a page takes 0.2 seconds to generate, one entry process can serve about five such requests per second. A limit of 20 or 30 can therefore serve a lot of visitors, as long as pages are fast or cached. Slow pages, long-running scripts and bots hammering uncached URLs fill entry processes quickly.
How to read your usage
In cPanel on CloudLinux servers, open Resource Usage (sometimes under "Metrics"). It shows:
- a summary of whether any limit was reached in the last 24 hours;
- graphs of CPU, memory, entry processes and I/O over time;
- the number of "faults", meaning times a limit was hit.
Occasional short peaks are normal. Frequent faults at the same times of day, or a constant line near the limit, mean the site needs attention.
Common causes of high usage
- No page caching, so every visit runs PHP and database queries. See website caching explained.
- Heavy plugins, such as related-post engines, statistics plugins or poorly written page builders.
- WP-Cron firing on every page load on busy WordPress sites.
- Bots and scrapers crawling search, filter or calendar pages that cannot be cached.
- WooCommerce cart fragments and admin-ajax requests; see how to speed up WooCommerce.
- Backup or import jobs running during busy hours.
- A compromised site sending spam or running malicious scripts. See website malware signs.
How to bring usage down
- Enable full-page caching, and make sure it actually serves cached pages (check response headers).
- Move WP-Cron to a real cron job: disable the built-in trigger and run
wp-cron.phpevery few minutes from cPanel's Cron Jobs. - Find the slow plugin: disable plugins one by one on a staging copy, or use a profiling plugin briefly.
- Block abusive bots with a firewall rule, or rate-limit expensive URLs.
- Use a current PHP version; see which PHP version should your website use.
- Clean up inodes: old backups, cache folders and email you no longer need.
- Schedule heavy jobs such as backups and imports outside busy hours.
When to upgrade instead
Upgrade when the site is already optimised and you still see regular faults, or when legitimate traffic has grown steadily. A larger shared hosting plan, cloud hosting or a VPS raises or removes the per-account ceiling; the comparison in shared hosting vs VPS helps you decide.
Frequently Asked Questions
Why does my site show "508 Resource Limit Is Reached"?
Usually because the entry process limit was reached: too many requests were being processed at once. Caching, blocking bad bots and fixing slow pages are the main fixes. See common hosting errors explained.
Does upgrading PHP reduce resource usage?
Often yes. Newer PHP versions are generally more efficient, so the same page needs less CPU. Test compatibility first.
Do email and cron jobs count towards my limits?
Processes run by your account, including cron jobs, generally count towards your process and CPU limits, and stored email counts towards inodes and disk space.
Related reading
Start with what is web hosting for the fundamentals, then read why is my website slow for a full troubleshooting routine.
Sources
Last updated 7 October 2026
