105 lines
3.5 KiB
Markdown
105 lines
3.5 KiB
Markdown
---
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---
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{% capture overview %}
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This page shows how assign CPU and RAM resources to containers running
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in a Kubernetes Pod.
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{% endcapture %}
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{% capture prerequisites %}
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{% include task-tutorial-prereqs.md %}
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{% endcapture %}
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{% capture steps %}
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### Assigning CPU and RAM resources to a container
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When you create a Pod, you can request CPU and RAM resources for the containers
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that run in the Pod. You can also set limits for CPU and RAM resources. To
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request CPU and RAM resources, include the `resources:requests` field in the
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configuration file. To set limits on CPU and RAM resources, include the
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`resources:limits` field.
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Kubernetes schedules a Pod to run on a Node only if the Node has enough CPU and
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RAM available to satisfy the total CPU and RAM requested by all of the
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containers in the Pod. Also, as a container runs on a Node, Kubernetes doesn't
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allow the CPU and RAM consumed by the container to exceed the limits you specify
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for the container. If a container exceeds its RAM limit, it is terminated. If a
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container exceeds its CPU limit, it becomes a candidate for having its CPU use
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throttled.
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In this exercise, you create a Pod that runs one container. The configuration
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file for the Pod requests 250 milicpu and 64 mebibytes of RAM. It also sets
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upper limits of 1 cpu and 128 mebibytes of RAM. Here is the configuration file
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for the `Pod`:
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{% include code.html language="yaml" file="cpu-ram.yaml" ghlink="/docs/tasks/configure-pod-container/cpu-ram.yaml" %}
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1. Create a Pod based on the YAML configuration file:
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export REPO=https://raw.githubusercontent.com/kubernetes/kubernetes.github.io/master
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kubectl create -f $REPO/docs/tasks/configure-pod-container/cpu-ram.yaml
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1. Display information about the pod:
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kubectl describe pod cpu-ram-demo
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The output is similar to this:
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Name: cpu-ram-demo
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...
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Containers:
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cpu-ram-demo-container:
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...
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Limits:
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cpu: 1
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memory: 128Mi
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Requests:
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cpu: 250m
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memory: 64Mi
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### Understanding CPU and RAM units
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The CPU resource is measured in *cpu*s. Fractional values are allowed. You can
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use the suffix *m* to mean mili. For example 100m cpu is 100 milicpu, and is
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the same as 0.1 cpu.
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The RAM resource is measured in bytes. You can express RAM as a plain integer
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or a fixed-point integer with one of these suffixes: E, P, T, G, M, K, Ei, Pi,
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Ti, Gi, Mi, Ki. For example, the following represent approximately the same value:
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128974848, 129e6, 129M , 123Mi
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### If you don't specify limits or requests
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If you don't specify a RAM limit, Kubernetes places no upper bound on the
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amount of RAM a Container can use. A Container could use all the RAM
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available on the Node where the Container is running. Similarly, if you don't
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specify a CPU limit, Kubernetes places no upper bound on CPU resources, and a
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Container could use all of the CPU resources available on the Node.
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For information about why you would want to specify limits, see
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[Setting Pod CPU and Memory Limits](/docs/admin/limitrange/).
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For information about what happens if you don't specify CPU and RAM requests, see
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[Resource Requests and Limits of Pod and Container](/docs/user-guide/compute-resources/).
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{% endcapture %}
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{% capture whatsnext %}
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* Learn more about [managing compute resources](/docs/user-guide/compute-resources/).
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* See [ResourceRequirements](/docs/api-reference/v1/definitions/#_v1_resourcerequirements).
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{% endcapture %}
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{% include templates/task.md %}
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