272 lines
8.7 KiB
Markdown
272 lines
8.7 KiB
Markdown
---
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title: Configure Minimum and Maximum Memory Constraints for a Namespace
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---
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{% capture overview %}
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This page shows how to set minimum and maximum values for memory used by Containers
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running in a namespace. You specify minimum and maximum memory values in a
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[LimitRange](/docs/api-reference/v1.6/#limitrange-v1-core)
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object. If a Pod does not meet the constraints imposed by the LimitRange,
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it cannot be created in the namespace.
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{% endcapture %}
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{% capture prerequisites %}
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{% include task-tutorial-prereqs.md %}
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Each node in your cluster must have at least 1 GiB of memory.
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{% endcapture %}
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{% capture steps %}
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## Create a namespace
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Create a namespace so that the resources you create in this exercise are
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isolated from the rest of your cluster.
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```shell
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kubectl create namespace constraints-mem-example
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```
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## Create a LimitRange and a Pod
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Here's the configuration file for a LimitRange:
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{% include code.html language="yaml" file="memory-constraints.yaml" ghlink="/docs/tasks/administer-cluster/memory-constraints.yaml" %}
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Create the LimitRange:
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```shell
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kubectl create -f https://k8s.io/docs/tasks/administer-cluster/memory-constraints.yaml --namespace=constraints-mem-example
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```
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View detailed information about the LimitRange:
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```shell
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kubectl get limitrange cpu-min-max-demo --namespace=constraints-mem-example --output=yaml
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```
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The output shows the minimum and maximum memory constraints as expected. But
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notice that even though you didn't specify default values in the configuration
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file for the LimitRange, they were created automatically.
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```
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limits:
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- default:
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memory: 1Gi
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defaultRequest:
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memory: 1Gi
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max:
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memory: 1Gi
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min:
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memory: 500Mi
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type: Container
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```
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Now whenever a Container is created in the constraints-mem-example namespace, Kubernetes
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performs these steps:
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* If the Container does not specify its own memory request and limit, assign the default
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memory request and limit to the Container.
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* Verify that the Container has a memory request that is greater than or equal to 500 MiB.
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* Verify that the Container has a memory limit that is less than or equal to 1 GiB.
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Here's the configuration file for a Pod that has one Container. The Container manifest
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specifies a memory request of 600 MiB and a memory limit of 800 MiB. These satisfy the
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minimum and maximum memory constraints imposed by the LimitRange.
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{% include code.html language="yaml" file="memory-constraints-pod.yaml" ghlink="/docs/tasks/administer-cluster/memory-constraints-pod.yaml" %}
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Create the Pod:
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```shell
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kubectl create -f https://k8s.io/docs/tasks/administer-cluster/memory-constraints-pod.yaml --namespace=constraints-mem-example
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```
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Verify that the Pod's Container is running:
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```shell
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kubectl get pod constraints-mem-demo --namespace=constraints-mem-example
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```
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View detailed information about the Pod:
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```shell
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kubectl get pod constraints-mem-demo --output=yaml --namespace=constraints-mem-example
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```
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The output shows that the Container has a memory request of 600 MiB and a memory limit
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of 800 MiB. These satisfy the constraints imposed by the LimitRange.
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```yaml
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resources:
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limits:
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memory: 800Mi
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requests:
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memory: 600Mi
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```
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Delete your Pod:
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```shell
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kubectl delete pod constraints-mem-demo --namespace=constraints-mem-example
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```
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## Attempt to create a Pod that exceeds the maximum memory constraint
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Here's the configuration file for a Pod that has one Container. The Container specifies a
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memory request of 700 MiB and a memory limit of 1.5 GiB.
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{% include code.html language="yaml" file="memory-constraints-pod-2.yaml" ghlink="/docs/tasks/administer-cluster/memory-constraints-pod-2.yaml" %}
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Attempt to create the Pod:
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```shell
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kubectl create -f https://k8s.io/docs/tasks/administer-cluster/memory-constraints-pod-2.yaml --namespace=constraints-mem-example
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```
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The output shows that the Pod does not get created, because the Container specifies a memory limit that is
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too large:
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```
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Error from server (Forbidden): error when creating "docs/tasks/administer-cluster/memory-constraints-pod-2.yaml":
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pods "constraints-mem-demo-2" is forbidden: maximum memory usage per Container is 1Gi, but limit is 1536Mi.
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```
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## Attempt to create a Pod that does not meet the minimum memory request
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Here's the configuration file for a Pod that has one Container. The Container specifies a
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memory request of 200 MiB and a memory limit of 800 MiB.
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{% include code.html language="yaml" file="memory-constraints-pod-3.yaml" ghlink="/docs/tasks/administer-cluster/memory-constraints-pod-3.yaml" %}
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Attempt to create the Pod:
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```shell
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kubectl create -f https://k8s.io/docs/tasks/administer-cluster/memory-constraints-pod-3.yaml --namespace=constraints-mem-example
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```
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The output shows that the Pod does not get created, because the Container specifies a memory
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request that is too small:
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```
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Error from server (Forbidden): error when creating "docs/tasks/administer-cluster/memory-constraints-pod-3.yaml":
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pods "constraints-mem-demo-3" is forbidden: minimum memory usage per Container is 500Mi, but request is 100Mi.
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```
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## Create a Pod that does not specify any CPU request or limit
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Here's the configuration file for a Pod that has one Container. The Container does not
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specify a memory request, and it does not specify a memory limit.
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{% include code.html language="yaml" file="memory-constraints-pod-4.yaml" ghlink="/docs/tasks/administer-cluster/memory-constraints-pod-4.yaml" %}
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Create the Pod:
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```shell
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kubectl create -f https://k8s.io/docs/tasks/administer-cluster/memory-constraints-pod-4.yaml --namespace=constraints-mem-example
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```
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View detailed information about the Pod:
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```
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kubectl get pod constraints-mem-demo-4 --namespace=constraints-mem-example --output=yaml
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```
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The output shows that the Pod's Container has a memory request of 1 GiB and a memory limit of 1 GiB.
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How did the Container get those values?
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```
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resources:
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limits:
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memory: 1Gi
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requests:
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memory: 1Gi
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```
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Because your Container did not specify its own memory request and limit, it was given the
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[default memory request and limit](/docs/tasks/administer-cluster/default-memory-request-limit/)
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from the LimitRange.
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At this point, your Container might be running or it might not be running. Recall that a prerequisite
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for this task is that your Nodes have at least 1 GiB of memory. If each of your Nodes has only
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1 GiB of memory, then there is not enough allocatable memory on any Node to accommodate a memory
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request of 1 GiB. If you happen to be using Nodes with 2 GiB of memory, then you probably have
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enough space to accommodate the 1 GiB request.
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Delete your Pod:
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```
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kubectl delete pod constraints-mem-demo-4 --namespace=constraints-mem-example
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```
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## Enforcement of minimum and maximum memory constraints
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The maximum and minimum memory constraints imposed on a namespace by a LimitRange are enforced only
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when a Pod is created or updated. If you change the LimitRange, it does not affect
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Pods that were created previously.
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## Motivation for minimum and maximum memory constraints
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As a cluster administrator, you might want to impose restrictions on the amount of memory that Pods can use.
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For example:
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* Each Node in a cluster has 2 GB of memory. You do not want to accept any Pod that requests
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more than 2 GB of memory, because no Node in the cluster can support the request.
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* A cluster is shared by your production and development departments.
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You want to allow production workloads to consume up to 8 GB of memory, but
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you want development workloads to be limited to 512 MB. You create separate namespaces
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for production and development, and you apply memory constraints to each namespace.
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## Clean up
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Delete your namespace:
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```shell
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kubectl delete namespace constraints-mem-example
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```
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{% endcapture %}
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{% capture whatsnext %}
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### For cluster administrators
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* [Configure Default Memory Requests and Limits for a Namespace](/docs/tasks/administer-cluster/memory-default-namespace/)
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* [Configure Default CPU Requests and Limits for a Namespace](/docs/tasks/administer-cluster/default-cpu-request-limit/)
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* [Configure Minimum and Maximum CPU Constraints for a Namespace](/docs/tasks/administer-cluster/cpu-constraint-namespace/)
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* [Configure Memory and CPU Quotas for a Namespace](/docs/tasks/administer-cluster/quota-memory-cpu-namespace/)
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* [Configure a Pod Quota for a Namespace](/docs/tasks/administer-cluster/quota-pod-namespace/)
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* [Configure Quotas for API Objects](/docs/tasks/administer-cluster/quota-api-object/)
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### For app developers
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* [Assign Memory Resources to Containers and Pods](/docs/tasks/configure-pod-container/assign-memory-resource/)
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* [Assign CPU Resources to Containers and Pods](/docs/tasks/configure-pod-container/assign-cpu-resource/)
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* [Configure Quality of Service for Pods](/docs/tasks/configure-pod-container/quality-service-pod/)
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{% endcapture %}
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{% include templates/task.md %}
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