What is the difference between "user" and "sys" CPU usage?

Posted April 9, 2017 12.4k views
Server OptimizationDigitalOceanControl PanelsUbuntu 16.04

I noticed that on the dashboard that one of my droplets spiked to >800% of “sys” CPU usage. It occasionally does this for very brief periods of time, and happens to occur at the same time as some high disk IO and network IO. It’s not causing me any troubles as far as I can tell but I was just wondering what “sys” CPU usage actually means. I was initially under the impression that it’s kernel processing load vs userspace load, but since it’s going well over 100% I’m not sure what it actually means.

It’s a single-core 1GB droplet.

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Depending on what you’re using to view output – top, glances, htop, etc – labeling may be a little different, though if you’re referring to a line that looks something like (top on a Droplet):

%Cpu(s):  0.0 us,  0.0 sy,  0.0 ni,100.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st

Then us refers to time spent in user space and sy refers to time spent in kernel space.

This is a new Droplet that’s used for testing, so there’s really not much activity going on here, but if I were installing software or running more intensive processes, I’d see those numbers jumping around a bit.

Seeing a short spike isn’t a major issue, but if you’re seeing an 800% jump, then you need to find out what is causing the issue and see what can be done to resolve it. It may very well be that you simply don’t have enough CPU to quickly handle the tasks that are being ran, thus you’re overloading the single CPU core that you currently have.