Ndtyjky

I don't really understand this after read through the document. Some use term like "CPU" but some use "core".

I am running Kubernetes in my laptop for testing purpose, my laptop has one CPU (2.2 Ghz) and 4 cores.

My question is, if I want to set the CPU request/limit for pod, the maximum resource that I have should be 1000m or 4000m?

Can anyone explain the difference (CPU vs Core) here in Kubernetes context?

To remove any guess work regarding your laptop or any other environment, execute

kubectl get nodes

...and then this for a particular node:

kubectl describe node <node-name>

Look for cpu under Allocatable (which may have the same value as under Capacity).

Take into consideration that

1 CPU = 1000 millicores/millicpu

when setting "fractional" resources.requests.cpu and resources.limits.cpu for containers.

To clarify what's described here in the Kubernetes context, 1 CPU is the same as a core.

1000m (milicores) = 1 core = 1 CPU = 1 AWS vCPU = 1 GCP Core.

100m (milicores) = 0.1 core = 0.1 CPU = 0.1 AWS vCPU = 0.1 GCP Core.

For example, an Intel Core i7-6700 has 4 cores but it has Hyperthreading which doubles what the system sees in terms of cores. So in essence, it will show up in Kubernetes as:

8000m = 8 cores = 8 CPUs

Some extra info, these resources are managed by the kube-scheduler using the Completely Fair Scheduler (CFS) and the are no guarantees in terms of overruns within the same machine and your pod may be moved around.

If you'd like to have stronger guarantees you might consider the --cpu-manager-policy=static (CPU Manager) option in the kubelet. More information here and here.

As mentioned here, https://kubernetes.io/docs/tasks/configure-pod-container/assign-cpu-resource/

It clearly says that,

The CPU resource is measured in CPU units. One CPU, in Kubernetes, is equivalent to:



1 AWS vCPU

1 GCP Core

1 Azure vCore

1 Hyperthread on a bare-metal Intel processor with Hyperthreading

So, setting argument -cpus "2" tells the Container to attempt to use 2 CPUs.

Also, CPU is always requested as an absolute quantity, never as a relative quantity; 0.1 is the same amount of CPU on a single-core, dual-core, or 48-core machine.

Thank Rico for explaining the CPU vs Core in Kubernetes context.

I personally think that apisim solution is more suitable for my problem.

I run the commands and find out I only have 2 allocatable cores:

I couldn't understand why until I found this:

Rico is right about my laptop should have 8 cores due to Hyperthreading. But the docker default settings throttle it to 2.

Hope this help others.