Metric-server cpu and memory units

General Discussions
1

Using metrics server I am getting cpu and memory usage of a pod.
for ex: “usage”:{“cpu”:“576285n”,“memory”:“182792Ki”}
Wanted to know what is the unit of cpu usage and memory here?
Is the metric value returned is CPU usage%?

2

n stands for “nanocores” or “nanoCPU”. Kubernetes CPU metrics are generally “expressed” when a person deals with them in millicores/milliCPU, or 1/1000 of a cpu. a nanocore/nanoCPU is 1/1000000000 (1 billionth) of a cpu. for a little more info the docs have a section on CPU Units but they only really describe millicores/milliCPU.

Ki is a Kibibyte. Kubernetes supports both Binary Units and Metric Units when writing pod specs and such, but for metrics things are emitted as Binary Units.

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3

Can we convert this nanocores to CPU usage percentage?

4

It sort of is. Millicores came about to be a better approximation of CPU since “true” CPU% or allocation can vary depending on the platform.

Think of cpu usage set to 50%. 50% means different things on a system with 1 core vs 8 cores. With Millicores 1000m will always equal 1 core. If you see something consuming 750m you know it is roughly 75% of a single core. With that, if you want to approximate CPU %, you would:

current millicore usage / (cores * 1000)

Hope that makes sense :sweat_smile:

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5

I’d add that for me it was also relevant to know which percentage of the requested to that pod was used by that pod.

So, instead of dividing by cores *1000, just divide by the requested.

Both numbers might be useful, in my case this one was more useful for developers so they knew they when they were using a big percentage of what was guaranteed and react (either reduce cpu usage or increase the request).

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6

Thanks @mrbobbytables and @rata. This helped me alot. :slight_smile: