When a website slows down, CPU throttling, CPU steal, and load average can help identify the cause. CPU saturation, provider throttling, CPU steal, and a high load average can produce similar symptoms, but each requires a different response. Reading these measurements together helps show whether the website needs optimization, more resources, or an investigation by the hosting provider.
Table of Contents
What the four measurements mean
CPU saturation means the website is using most or all of the CPU available to it. The workload itself is consuming the processing capacity. On mybox, high CPU load is often an early sign that a WordPress website is outgrowing its current configuration. The cause may be a plugin, theme component, database query, or external resource rather than WordPress core itself. See How to Check What Is Slowing Down a WordPress Website.
CPU throttling is a restriction applied by the hosting environment. The website may continue to create work, but the available CPU time is limited, so requests take longer to complete. On mybox, high CPU usage can lead to higher costs or, in extreme cases, temporary performance throttling. The relevant explanation is covered in WordPress High CPU Load: Causes and Effective Solutions.
CPU steal is CPU time that the virtual server expected to receive but did not receive because the underlying physical CPU was serving another virtual workload. It is therefore different from CPU time used by the website. A high steal value points toward contention in the virtualized hosting environment, rather than proving that a plugin or application generated too much work.
Load average shows how much work is waiting to run or finish. It is not a CPU percentage. A high load average can result from CPU pressure, but it can also be caused by disk contention or processes waiting on other work. For this reason, load average alone cannot identify the source of a slowdown.
How to distinguish the likely cause
| Pattern | What it suggests | First response |
|---|---|---|
| CPU use stays high and CPU steal stays low | The website workload is using the available processing capacity. | Inspect the website for a plugin, theme component, database query, or external resource that creates the load. |
| CPU use is limited while throttling is reported | The hosting environment is restricting CPU time. | Review the resource situation and consider whether the current configuration is large enough for the website. |
| CPU steal is high during the slowdown | The virtual server is not receiving all the CPU time it requested. | Record the timing and measurements, then ask the hosting provider to investigate the host environment. |
| Load average is high but CPU use does not explain it | Processes may be waiting on disk activity or other process contention. | Check disk and process activity before treating the issue as a CPU capacity problem. |
Which measurements to check together
Start with CPU usage, CPU steal, load average, and the state of the processes creating the load. Compare the readings while the site is slow with readings during normal operation. A single sample can be misleading. A repeated pattern is more useful because it shows whether the condition is tied to the website workload, the hosting environment, or waiting processes.
For WordPress, also identify the application component behind the work. Query Monitor can help identify performance bottlenecks, including a specific plugin, theme component, database query, or external resource. The mybox article How to Check What Is Slowing Down a WordPress Website describes this approach.
When to optimize, upgrade, or contact mybox
Optimize the website when the workload is the cause
Optimization is the appropriate first step when CPU use is consistently high, CPU steal is not the main pattern, and one or more website components account for the work. Investigate the plugin, theme component, database query, or external resource linked to the slowdown. A slow website can also have causes in the website itself or the server it runs on, as described in Why Is My Website Running Slowly?
Consider a larger configuration when demand has outgrown the current one
A plan or configuration change is relevant when the website continues to need more CPU after its main workload has been reviewed. High CPU load on mybox can indicate that a WordPress site is outgrowing its current configuration. This is also the situation in which higher costs or temporary throttling may occur, so review the resource pattern before changing the configuration.
Ask the hosting provider to investigate environment-related symptoms
Contact mybox when CPU steal remains high during the slowdown, when throttling appears without a matching change in website activity, or when load average is high and the website workload does not account for it. Include the time of the event and the CPU usage, CPU steal, load average, and process or disk observations. These details help separate website demand from contention in the hosting environment.
Key distinction
High CPU usage means the website is consuming processing capacity. Throttling means the hosting environment is limiting available CPU time. CPU steal means expected CPU time is being taken by other virtual workloads. Load average measures waiting work and can rise because of CPU, disk, or process contention. The correct response depends on which pattern appears consistently.