What is CPU Steal?
Sometimes a server feels slow even when the application looks fine. One common reason, especially on virtual machines, is CPU steal.
CPU steal time happens when your virtual server is ready to run, but the physical host is busy running other virtual machines first. In simple terms, your server is waiting while someone else is using the processor.
How this tool helps
Web browsers cannot read real CPU steal time directly. However, this tool runs controlled CPU load and measures scheduling lag, which shows how delayed your system becomes when trying to execute work.
If the lag is consistently high during the test, it may indicate CPU contention, host overload, or a busy VM environment. It is a quick way to check if the system is struggling before blaming the application.
Come back from your VM
You’re visiting from a mobile device. This CPU Contention Test works best when run from a virtual machine (VM).
Please come back from your VM to run the full performance test and get accurate results.
CPU Contention & Performance Test
Runs CPU load in your browser and measures scheduling lag. High lag may indicate CPU contention or VM host overload.
Tip: run the test in the foreground tab. Background tabs can be throttled by the browser.
How to use
- Set Duration (recommended 60 to 120 seconds).
- Start with Workers 2 to 4 and Load 50 to 70%.
- Click Start Test. Keep this tab active.
- Let it run until the countdown finishes. A results page will appear.
- If needed, increase workers or load and run again to compare.