k8s 能做到限制pod在节点的指定cpu核心上运行吗？给出一个具体案例

是的，Kubernetes可以限制Pod在节点的指定CPU核心上运行。这可以通过使用CPUManager和TopologyManager来实现。

首先，需要启用kubelet的CPUManager和TopologyManager特性。然后，可以在调度器yaml文件中配置所需的CPU核心。

以下是一个使用CPUManager和TopologyManager限制Pod在节点的指定CPU核心上运行的具体案例：

1. 创建Node并打上特定的label。比如：

$ kubectl label node <node-name> nodetype=compute

2. 在pod的yaml文件中指定Pod的CPU Manager和Topology Manager配置。

apiVersion: v1
kind: Pod
metadata:
  name: example
  labels:
    app: example
spec:
  containers:
  - name: example
    image: nginx
    resources:
      limits:
        cpu: 2000m
    command:
      - nginx
    args:
      - "-c"
      - "/etc/nginx/nginx.conf"
    volumeMounts:
    - name: "example"
      mountPath: "/etc/nginx"
  affinity:
    nodeAffinity:
      requiredDuringSchedulingIgnoredUnknowns:
        nodeSelectorTerms:
        - matchExpressions:
            - key: nodetype
              operator: In
              values:
              - compute
  topologySpreadConstraints:
    - maxSkew: 1
      topologyKey: "kubernetes.io/hostname"
      whenUnsatisfiable: DoNotSchedule
      labelSelector:
        matchExpressions:
        - key: nodetype
          operator: In
          values:
          - compute
    - maxSkew: 1
      topologyKey: "topology.kubernetes.io/zone"
      whenUnsatisfiable: DoNotSchedule
      labelSelector:
        matchExpressions:
        - key: nodetype
          operator: In
          values:
          - compute
    - maxSkew: 1
      topologyKey: "topology.kubernetes.io/region"
      whenUnsatisfiable: DoNotSchedule
      labelSelector:
        matchExpressions:
        - key: nodetype
          operator: In
          values:
          - compute

在上述yaml文件中，Pod的CPU Manager和Topology Manager配置项为：

resources:
  limits:
    cpu: 2000m

topologySpreadConstraints:
- maxSkew: 1
  topologyKey: "kubernetes.io/hostname"
  whenUnsatisfiable: DoNotSchedule
  labelSelector:
    matchExpressions:
    - key: nodetype
      operator: In
      values:
      - compute
- maxSkew: 1
  topologyKey: "topology.kubernetes.io/zone"
  whenUnsatisfiable: DoNotSchedule
  labelSelector:
    matchExpressions:
    - key: nodetype
      operator: In
      values:
      - compute
- maxSkew: 1
  topologyKey: "topology.kubernetes.io/region"
  whenUnsatisfiable: DoNotSchedule
  labelSelector:
    matchExpressions:
    - key: nodetype
      operator: In
      values:
      - compute

其中，Pod的yaml文件中的topologySpreadConstraints中的配置项表示，将Pod调度到同一Zone、同一Region和同一节点的Pod数量最大允许偏差为1，即一组的最大和最小值在1个Pod以内。

该示例展示了在Kubernetes中使用CPUManager和TopologyManager来限制Pod在节点的指定CPU核心上运行的具体步骤和方法。