Made CPU usage consistent and removed apostrophes (#10044)
* Made CPU usage consistent and removed apostrophes * Update assign-cpu-resource.md
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Julie Bruce
k8s-ci-robot
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@ -18,11 +18,11 @@ but is not allowed to use more CPU than its limit.
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{{< include "task-tutorial-prereqs.md" >}} {{< version-check >}}
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Each node in your cluster must have at least 1 cpu.
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Each node in your cluster must have at least 1 CPU.
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A few of the steps on this page require you to run the
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[metrics-server](https://github.com/kubernetes-incubator/metrics-server)
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service in your cluster. If you don't have metrics-server
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service in your cluster. If you do not have the metrics-server
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running, you can skip those steps.
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If you are running minikube, run the following command to enable
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@ -33,7 +33,7 @@ minikube addons enable metrics-server
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```
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To see whether metrics-server (or another provider of the resource metrics
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API, `metrics.k8s.io`) is running, enter this command:
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API, `metrics.k8s.io`) is running, type the following command:
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```shell
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kubectl get apiservices
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@ -65,16 +65,14 @@ kubectl create namespace cpu-example
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## Specify a CPU request and a CPU limit
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To specify a CPU request for a Container, include the `resources:requests` field
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in the Container's resource manifest. To specify a CPU limit, include `resources:limits`.
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in the Container resource manifest. To specify a CPU limit, include `resources:limits`.
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In this exercise, you create a Pod that has one Container. The Container has a CPU
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request of 0.5 cpu and a CPU limit of 1 cpu. Here's the configuration file
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for the Pod:
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In this exercise, you create a Pod that has one Container. The Container has a request of 0.5 CPU and a limit of 1 CPU. Here is the configuration file for the Pod:
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{{< codenew file="pods/resource/cpu-request-limit.yaml" >}}
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In the configuration file, the `args` section provides arguments for the Container when it starts.
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The `-cpus "2"` argument tells the Container to attempt to use 2 cpus.
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The `args` section of the configuration file provides arguments for the Container when it starts.
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The `-cpus "2"` argument tells the Container to attempt to use 2 CPUs.
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Create the Pod:
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@ -82,7 +80,7 @@ Create the Pod:
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kubectl create -f https://k8s.io/examples/pods/resource/cpu-request-limit.yaml --namespace=cpu-example
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```
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Verify that the Pod's Container is running:
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Verify that the Pod Container is running:
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```shell
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kubectl get pod cpu-demo --namespace=cpu-example
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@ -94,8 +92,8 @@ View detailed information about the Pod:
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kubectl get pod cpu-demo --output=yaml --namespace=cpu-example
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```
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The output shows that the one Container in the Pod has a CPU request of 500 millicpu
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and a CPU limit of 1 cpu.
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The output shows that the one Container in the Pod has a CPU request of 500 milliCPU
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and a CPU limit of 1 CPU.
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```yaml
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resources:
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@ -111,37 +109,35 @@ Use `kubectl top` to fetch the metrics for the pod:
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kubectl top pod cpu-demo --namespace=cpu-example
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```
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The output shows that the Pod is using 974 millicpu, which is just a bit less than
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the limit of 1 cpu specified in the Pod's configuration file.
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The output shows that the Pod is using 974 milliCPU, which is just a bit less than
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the limit of 1 CPU specified in the Pod configuration file.
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```
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NAME CPU(cores) MEMORY(bytes)
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cpu-demo 974m <something>
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```
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Recall that by setting `-cpu "2"`, you configured the Container to attempt to use 2 cpus.
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But the Container is only being allowed to use about 1 cpu. The Container's CPU use is being
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throttled, because the Container is attempting to use more CPU resources than its limit.
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Recall that by setting `-cpu "2"`, you configured the Container to attempt to use 2 CPUs, but the Container is only being allowed to use about 1 CPU. The Container CPU use is being throttled, because the Container is attempting to use more CPU resources than its limit.
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{{< note >}}
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**Note:** There's another possible explanation for the CPU throttling. The Node might not have
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enough CPU resources available. Recall that the prerequisites for this exercise require that each of
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your Nodes has at least 1 cpu. If your Container is running on a Node that has only 1 cpu, the Container
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cannot use more than 1 cpu regardless of the CPU limit specified for the Container.
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**Note:** Another possible explanation for the CPU throttling is that the Node might not have
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enough CPU resources available. Recall that the prerequisites for this exercise require each of
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your Nodes ot have at least 1 CPU. If your Container runs on a Node that has only 1 CPU, the Container
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cannot use more than 1 CPU regardless of the CPU limit specified for the Container.
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{{< /note >}}
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## CPU units
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The CPU resource is measured in *cpu* units. One cpu, in Kubernetes, is equivalent to:
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The CPU resource is measured in *CPU* units. One CPU, in Kubernetes, is equivalent to:
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* 1 AWS vCPU
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* 1 GCP Core
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* 1 Azure vCore
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* 1 Hyperthread on a bare-metal Intel processor with Hyperthreading
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Fractional values are allowed. A Container that requests 0.5 cpu is guaranteed half as much
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CPU as a Container that requests 1 cpu. You can use the suffix m to mean milli. For example
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100m cpu, 100 millicpu, and 0.1 cpu are all the same. Precision finer than 1m is not allowed.
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Fractional values are allowed. A Container that requests 0.5 CPU is guaranteed half as much
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CPU as a Container that requests 1 CPU. You can use the suffix m to mean milli. For example
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100m CPU, 100 milliCPU, and 0.1 CPU are all the same. Precision finer than 1m is not allowed.
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CPU is always requested as an absolute quantity, never as a relative quantity; 0.1 is the same
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amount of CPU on a single-core, dual-core, or 48-core machine.
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@ -160,11 +156,11 @@ of the CPU requests for all the Containers in the Pod. Likewise, the CPU limit f
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a Pod is the sum of the CPU limits for all the Containers in the Pod.
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Pod scheduling is based on requests. A Pod is scheduled to run on a Node only if
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the Node has enough CPU resources available to satisfy the Pod’s CPU request.
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the Node has enough CPU resources available to satisfy the Pod CPU request.
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In this exercise, you create a Pod that has a CPU request so big that it exceeds
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the capacity of any Node in your cluster. Here is the configuration file for a Pod
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that has one Container. The Container requests 100 cpu, which is likely to exceed the
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that has one Container. The Container requests 100 CPU, which is likely to exceed the
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capacity of any Node in your cluster.
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{{< codenew file="pods/resource/cpu-request-limit-2.yaml" >}}
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@ -175,13 +171,13 @@ Create the Pod:
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kubectl create -f https://k8s.io/examples/pods/resource/cpu-request-limit-2.yaml --namespace=cpu-example
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```
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View the Pod's status:
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View the Pod status:
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```shell
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kubectl get pod cpu-demo-2 --namespace=cpu-example
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```
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The output shows that the Pod's status is Pending. That is, the Pod has not been
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The output shows that the Pod status is Pending. That is, the Pod has not been
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scheduled to run on any Node, and it will remain in the Pending state indefinitely:
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@ -215,9 +211,9 @@ Delete your Pod:
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kubectl delete pod cpu-demo-2 --namespace=cpu-example
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```
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## If you don’t specify a CPU limit
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## If you do not specify a CPU limit
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If you don’t specify a CPU limit for a Container, then one of these situations applies:
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If you do not specify a CPU limit for a Container, then one of these situations applies:
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* The Container has no upper bound on the CPU resources it can use. The Container
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could use all of the CPU resources available on the Node where it is running.
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@ -230,8 +226,8 @@ to specify a default value for the CPU limit.
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## Motivation for CPU requests and limits
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By configuring the CPU requests and limits of the Containers that run in your
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cluster, you can make efficient use of the CPU resources available on your cluster's
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Nodes. By keeping a Pod's CPU request low, you give the Pod a good chance of being
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cluster, you can make efficient use of the CPU resources available on your cluster
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Nodes. By keeping a Pod CPU request low, you give the Pod a good chance of being
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scheduled. By having a CPU limit that is greater than the CPU request, you accomplish two things:
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* The Pod can have bursts of activity where it makes use of CPU resources that happen to be available.
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