Kubernetes Prow Robot
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title: Pod QoS 类
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content_type: concept
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weight: 85
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---
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<!--
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title: Pod Quality of Service Classes
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content_type: concept
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weight: 85
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-->
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<!-- overview -->
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<!--
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This page introduces _Quality of Service (QoS) classes_ in Kubernetes, and explains
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how Kubernetes assigns a QoS class to each Pods as a consequence of the resource
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constraints that you specify for the containers in that Pod. Kubernetes relies on this
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classification to make decisions about which Pods to evict when there are not enough
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available resources on a Node.
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-->
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本页介绍 Kubernetes 中的 **服务质量（Quality of Service，QoS）** 类，
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阐述 Kubernetes 如何根据为 Pod 中的容器指定的资源约束为每个 Pod 设置 QoS 类。
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Kubernetes 依赖这种分类来决定当 Node 上没有足够可用资源时要驱逐哪些 Pod。
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<!-- body -->
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<!--
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## Quality of Service classes
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-->
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## QoS 类 {#qos-class}
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<!--
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Kubernetes classifies the Pods that you run and allocates each Pod into a specific
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_quality of service (QoS) class_. Kubernetes uses that classification to influence how different
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pods are handled. Kubernetes does this classification based on the
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[resource requests](/docs/concepts/configuration/manage-resources-containers/)
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of the {{< glossary_tooltip text="Containers" term_id="container" >}} in that Pod, along with
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how those requests relate to resource limits.
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This is known as {{< glossary_tooltip text="Quality of Service" term_id="qos-class" >}}
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(QoS) class. Kubernetes assigns every Pod a QoS class based on the resource requests
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and limits of its component Containers. QoS classes are used by Kubernetes to decide
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which Pods to evict from a Node experiencing
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[Node Pressure](/docs/concepts/scheduling-eviction/node-pressure-eviction/). The possible
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QoS classes are `Guaranteed`, `Burstable`, and `BestEffort`. When a Node runs out of resources,
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Kubernetes will first evict `BestEffort` Pods running on that Node, followed by `Burstable` and
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finally `Guaranteed` Pods. When this eviction is due to resource pressure, only Pods exceeding
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resource requests are candidates for eviction.
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-->
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Kubernetes 对你运行的 Pod 进行分类，并将每个 Pod 分配到特定的 **QoS 类**中。
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Kubernetes 使用这种分类来影响不同 Pod 被处理的方式。Kubernetes 基于 Pod
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中{{< glossary_tooltip text="容器" term_id="container" >}}的[资源请求](/zh-cn/docs/concepts/configuration/manage-resources-containers/)进行分类，
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同时确定这些请求如何与资源限制相关。
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这称为{{< glossary_tooltip text="服务质量" term_id="qos-class" >}} (QoS) 类。
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Kubernetes 基于每个 Pod 中容器的资源请求和限制为 Pod 设置 QoS 类。Kubernetes 使用 QoS
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类来决定从遇到[节点压力](/zh-cn/docs/concepts/scheduling-eviction/node-pressure-eviction/)的
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Node 中驱逐哪些 Pod。可选的 QoS 类有 `Guaranteed`、`Burstable` 和 `BestEffort`。
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当一个 Node 耗尽资源时，Kubernetes 将首先驱逐在该 Node 上运行的 `BestEffort` Pod，
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然后是 `Burstable` Pod，最后是 `Guaranteed` Pod。当这种驱逐是由于资源压力时，
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只有超出资源请求的 Pod 才是被驱逐的候选对象。
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### Guaranteed
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<!--
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Pods that are `Guaranteed` have the strictest resource limits and are least likely
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to face eviction. They are guaranteed not to be killed until they exceed their limits
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or there are no lower-priority Pods that can be preempted from the Node. They may
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not acquire resources beyond their specified limits. These Pods can also make
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use of exclusive CPUs using the
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[`static`](/docs/tasks/administer-cluster/cpu-management-policies/#static-policy) CPU management policy.
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-->
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`Guaranteed` Pod 具有最严格的资源限制，并且最不可能面临驱逐。
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在这些 Pod 超过其自身的限制或者从 Node 上没有可以抢占的低优先级 Pod 之前，
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这些 Pod 保证不会被杀死。这些 Pod 不可以获得超出其指定 limit 的资源。这些 Pod 也可以使用
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[`static`](/zh-cn/docs/tasks/administer-cluster/cpu-management-policies/#static-policy)
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CPU 管理策略来使用独占的 CPU。
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<!--
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#### Criteria
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For a Pod to be given a QoS class of `Guaranteed`:
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-->
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#### 判据
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Pod 被赋予 `Guaranteed` QoS 类的几个判据：
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<!--
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* Every Container in the Pod must have a memory limit and a memory request.
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* For every Container in the Pod, the memory limit must equal the memory request.
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* Every Container in the Pod must have a CPU limit and a CPU request.
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* For every Container in the Pod, the CPU limit must equal the CPU request.
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-->
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* Pod 中的每个容器必须有内存 limit 和内存 request。
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* 对于 Pod 中的每个容器，内存 limit 必须等于内存 request。
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* Pod 中的每个容器必须有 CPU limit 和 CPU request。
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* 对于 Pod 中的每个容器，CPU limit 必须等于 CPU request。
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### Burstable
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<!--
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Pods that are `Burstable` have some lower-bound resource guarantees based on the request, but
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do not require a specific limit. If a limit is not specified, it defaults to a
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limit equivalent to the capacity of the Node, which allows the Pods to flexibly increase
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their resources if resources are available. In the event of Pod eviction due to Node
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resource pressure, these Pods are evicted only after all `BestEffort` Pods are evicted.
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Because a `Burstable` Pod can include a Container that has no resource limits or requests, a Pod
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that is `Burstable` can try to use any amount of node resources.
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-->
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`Burstable` Pod 有一些基于 request 的资源下限保证，但不需要特定的 limit。
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如果未指定 limit，则默认为其 limit 等于 Node 容量，这允许 Pod 在资源可用时灵活地增加其资源。
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在由于 Node 资源压力导致 Pod 被驱逐的情况下，只有在所有 `BestEffort` Pod 被驱逐后
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这些 Pod 才会被驱逐。因为 `Burstable` Pod 可以包括没有资源 limit 或资源 request 的容器，
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所以 `Burstable` Pod 可以尝试使用任意数量的节点资源。
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<!--
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#### Criteria
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A Pod is given a QoS class of `Burstable` if:
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* The Pod does not meet the criteria for QoS class `Guaranteed`.
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* At least one Container in the Pod has a memory or CPU request or limit.
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-->
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#### 判据
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Pod 被赋予 `Burstable` QoS 类的几个判据：
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* Pod 不满足针对 QoS 类 `Guaranteed` 的判据。
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* Pod 中至少一个容器有内存或 CPU request 或 limit。
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### BestEffort
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<!--
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Pods in the `BestEffort` QoS class can use node resources that aren't specifically assigned
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to Pods in other QoS classes. For example, if you have a node with 16 CPU cores available to the
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kubelet, and you assign 4 CPU cores to a `Guaranteed` Pod, then a Pod in the `BestEffort`
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QoS class can try to use any amount of the remaining 12 CPU cores.
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The kubelet prefers to evict `BestEffort` Pods if the node comes under resource pressure.
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-->
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`BestEffort` QoS 类中的 Pod 可以使用未专门分配给其他 QoS 类中的 Pod 的节点资源。
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例如若你有一个节点有 16 核 CPU 可供 kubelet 使用，并且你将 4 核 CPU 分配给一个 `Guaranteed` Pod，
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那么 `BestEffort` QoS 类中的 Pod 可以尝试任意使用剩余的 12 核 CPU。
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如果节点遇到资源压力，kubelet 将优先驱逐 `BestEffort` Pod。
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<!--
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#### Criteria
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A Pod has a QoS class of `BestEffort` if it doesn't meet the criteria for either `Guaranteed`
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or `Burstable`. In other words, a Pod is `BestEffort` only if none of the Containers in the Pod have a
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memory limit or a memory request, and none of the Containers in the Pod have a
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CPU limit or a CPU request.
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Containers in a Pod can request other resources (not CPU or memory) and still be classified as
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`BestEffort`.
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-->
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#### 判据
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如果 Pod 不满足 `Guaranteed` 或 `Burstable` 的判据，则它的 QoS 类为 `BestEffort`。
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换言之，只有当 Pod 中的所有容器没有内存 limit 或内存 request，也没有 CPU limit 或
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CPU request 时，Pod 才是 `BestEffort`。Pod 中的容器可以请求（除 CPU 或内存之外的）
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其他资源并且仍然被归类为 `BestEffort`。
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<!--
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## Some behavior is independent of QoS class {#class-independent-behavior}
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Certain behavior is independent of the QoS class assigned by Kubernetes. For example:
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-->
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## 某些行为独立于 QoS 类 {#class-independent-behavior}
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某些行为独立于 Kubernetes 分配的 QoS 类。例如：
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<!--
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* Any Container exceeding a resource limit will be killed and restarted by the kubelet without
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affecting other Containers in that Pod.
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* If a Container exceeds its resource request and the node it runs on faces
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resource pressure, the Pod it is in becomes a candidate for [eviction](/docs/concepts/scheduling-eviction/node-pressure-eviction/).
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If this occurs, all Containers in the Pod will be terminated. Kubernetes may create a
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replacement Pod, usually on a different node.
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-->
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* 所有超过资源 limit 的容器都将被 kubelet 杀死并重启，而不会影响该 Pod 中的其他容器。
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* 如果一个容器超出了自身的资源 request，且该容器运行的节点面临资源压力，则该容器所在的 Pod
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就会成为被[驱逐](/zh-cn/docs/concepts/scheduling-eviction/node-pressure-eviction/)的候选对象。
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如果出现这种情况，Pod 中的所有容器都将被终止。Kubernetes 通常会在不同的节点上创建一个替代的 Pod。
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<!--
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* The resource request of a Pod is equal to the sum of the resource requests of
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its component Containers, and the resource limit of a Pod is equal to the sum of
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the resource limits of its component Containers.
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* The kube-scheduler does not consider QoS class when selecting which Pods to
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[preempt](/docs/concepts/scheduling-eviction/pod-priority-preemption/#preemption).
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Preemption can occur when a cluster does not have enough resources to run all the Pods
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you defined.
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-->
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* Pod 的资源 request 等于其成员容器的资源 request 之和，Pod 的资源 limit 等于其组成容器的资源 limit 之和。
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* kube-scheduler 在选择要[抢占](/zh-cn/docs/concepts/scheduling-eviction/pod-priority-preemption/#preemption)的
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Pod 时不考虑 QoS 类。当集群没有足够的资源来运行你所定义的所有 Pod 时，就会发生抢占。
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## {{% heading "whatsnext" %}}
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<!--
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* Learn about [resource management for Pods and Containers](/docs/concepts/configuration/manage-resources-containers/).
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* Learn about [Node-pressure eviction](/docs/concepts/scheduling-eviction/node-pressure-eviction/).
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* Learn about [Pod priority and preemption](/docs/concepts/scheduling-eviction/pod-priority-preemption/).
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* Learn about [Pod disruptions](/docs/concepts/workload/pods/disruptions/).
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* Learn how to [assign memory resources to containers and pods](/docs/tasks/configure-pod-container/assign-memory-resource/).
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* Learn how to [assign CPU resources to containers and pods](/docs/tasks/configure-pod-container/assign-cpu-resource/).
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* Learn how to [configure Quality of Service for Pods](/docs/tasks/configure-pod-container/quality-service-pod/).
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-->
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* 进一步了解[为 Pod 和容器管理资源](/zh-cn/docs/concepts/configuration/manage-resources-containers/)。
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* 进一步了解[节点压力驱逐](/zh-cn/docs/concepts/scheduling-eviction/node-pressure-eviction/)。
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* 进一步了解 [Pod 优先级和抢占](/zh-cn/docs/concepts/scheduling-eviction/pod-priority-preemption/)。
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* 进一步了解 [Pod 干扰](/zh-cn/docs/concepts/workloads/pods/disruptions/)。
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* 进一步了解如何[为容器和 Pod 分配内存资源](/zh-cn/docs/tasks/configure-pod-container/assign-memory-resource/)。
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* 进一步了解如何[为容器和 Pod 分配 CPU 资源](/zh-cn/docs/tasks/configure-pod-container/assign-cpu-resource/)。
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* 进一步了解如何[配置 Pod 的服务质量](/zh-cn/docs/tasks/configure-pod-container/quality-service-pod/)。
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