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Version: v1.3

Eviction Strategy base on Memory Usage


Koordinator supports the dynamic overcommitment from idle resources on node to low-priority Pods as Batch priority. In co-location scenarios, the actual memory resource usage of nodes is constantly changing. For incompressible resources such as memory, high resource usage of node may cause OOM, which results in the high-priority Pod got killed. Koordinator provides an eviction strategy based on the memory usage node. Koordlet will continuously detect the memory usage of node (Total-Available) in second-level granularity. When the resource memory usage of node is high, it will evict low-priority BE Pods to ensure the QoS of high-priority pods until the memory usage of node reduces below to the threshold (evictThreshold). During the eviction process, Pods with lower priority(Pod.Spec.Priority) will be selected first, and if the priority is the same, Pods which consume more memory will be evicted first.



Please make sure Koordinator components are correctly installed in your cluster. If not, please refer to Installation.

ComponentVersion Requirement

The eviction strategy is provided by Koordlet, which is disabled by default in feature-gate. Please make sure the BEMemoryEvict=true field has been added in the -feature-gates arguments of Koordlet as the example

Use Eviction Strategy base on Memory Usage

  1. Create a configmap.yaml file based on the following ConfigMap content:

    #ConfigMap slo-controller-config example。
    apiVersion: v1
    kind: ConfigMap
    name: slo-controller-config # name should be set as the configuration of koord-manager, e.g. ack-slo-config
    namespace: koordinator-system # namespace should be set as the configuration of installation, e.g. kube-system
    # enable the eviction strategy base on Memory Usage
    resource-threshold-config: |
    "clusterStrategy": {
    "enable": true,
    "memoryEvictThresholdPercent": 70
    Configuration itemParameterValid valuesDescription
    enableBooleantrue; falsetrue:enable the eviction.; false(default):disable the eviction.
    memoryEvictThresholdPercentInt0~100eviction threshold percent of node memory usage, default is 70.
  2. Check whether a ConfigMap named slo-controller-config exists in the koordinator-system namespace.

  • If a ConfigMap named slo-controller-config exists, we commend that you run the kubectl patch command to update the ConfigMap. This avoids changing other settings in the ConfigMap.

    kubectl patch cm -n koordinator-system slo-controller-config --patch "$(cat configmap.yaml)"
  • If no ConfigMap named slo-controller-config exists, run the kubectl patch command to create a ConfigMap named ack-slo-config:

    kubectl apply -f configmap.yaml
  1. Create a file named be-pod-demo.yaml based on the following YAML content:

    apiVersion: v1
    kind: Pod
    name: be-pod-demo
    labels: 'BE' # set Pod QoS as BE
    - args:
    - '-c'
    - '1'
    - '--vm'
    - '1'
    - stress
    image: polinux/stress
    imagePullPolicy: Always
    name: stress
    restartPolicy: Always
    schedulerName: default-scheduler
  2. Run the following command to deploy the be-pod-demo pod in the cluster:

    kubectl apply -f be-pod-demo.yaml
  3. Run the following command to check the be-pod-demo pod in Running state:

    $ kubectl get pod be-pod-demo
    be-pod-demo 1/1 Running 0 7s
  4. Run the following command through stress tool make sure the memory usage of node is above the threshold config, and the argument --vm-bytes means the process will consume 10GB memory, this should be adjusted according to the node capacity.

    $ stress --cpu 1 --vm 1 --vm-bytes 10G --vm-keep
  5. Check the running state of be-pod-demo, then you can find the be-pod-demo pod is not exist, and the eviction information can be found in events.

    $ kubectl get pod be-pod-demo
    Error from server (NotFound): pods "be-pod-demo" not found

    $ kubectl get event
    46s Normal Killing pod/be-pod-demo Stopping container stress
    48s Warning evictPodSuccess ${your-pod-object} evict Pod:be-pod-demo, reason: EvictPodByNodeMemoryUsage, message: killAndEvictBEPods for node(${your-node-id}), need to release memory: 8077889699