Topology-aware scheduling for GPU workloads in Managed Service for Kubernetes®

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Prerequisites

1. Create a Managed Service for Kubernetes cluster and attach at least one GPU node group to it.
2. Install kubectl.
3. Connect to the cluster by using kubectl.

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How to view topology labels in your cluster

kubectl get nodes -L topology.nebius.com/gpu-cluster-id,topology.nebius.com/tier-2,topology.nebius.com/tier-1,kubernetes.io/hostname

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Example output

NAME                                 STATUS   ROLES    AGE    VERSION   GPU-CLUSTER-ID                         TIER-2                             TIER-1                             HOSTNAME
computeinstance-e00f4wsk77x4vsr58s   Ready    <none>   144d   v1.32.9   computegpucluster-e00agxzkvne8558nv8   959d125cbd887219574193fdba27b2c8   282cfcbf8e735653e4ce9884052cb523   computeinstance-e00f4wsk77x4vsr58s
computeinstance-e00nm33x3y9597zzxj   Ready    <none>   54d    v1.32.9                                                                                                                computeinstance-e00nm33x3y9597zzxj
computeinstance-e00tw5jypq4zvfrsrx   Ready    <none>   77d    v1.32.9   computegpucluster-e00z7ftxx6dacdbra5   5ca19afc3d62844695b08033aeba635b   297bbb6a0db40d875c266b589dc95f5b   computeinstance-e00tw5jypq4zvfrsrx
computeinstance-e00v7g42bam61yqzp3   Ready    <none>   144d   v1.32.9   computegpucluster-e00agxzkvne8558nv8   959d125cbd887219574193fdba27b2c8   04011d5d2b17ec74672df94efbbeeb15   computeinstance-e00v7g42bam61yqzp3

• computeinstance-e00f4wsk77x4vsr58s and computeinstance-e00v7g42bam61yqzp3 share the same GPU-CLUSTER-ID and TIER-2 values, which means they belong to the same high-speed network domain and the same wider network locality domain. These nodes have different TIER-1 values, which indicates that they belong to different lower-level locality domains.
• computeinstance-e00tw5jypq4zvfrsrx belongs to a different GPU cluster and topology hierarchy because all of its topology label values are different.
• computeinstance-e00nm33x3y9597zzxj does not have topology labels. This usually means that the node is not attached to a GPU cluster, or TAS is not enabled.

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How to enable topology-aware scheduling

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Steps

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Install and configure Kueue

1. Install Kueue.
2. Enable TAS:
   kubectl -n kueue-system patch deployment kueue-controller-manager \
    --type json \
    -p='[{"op": "add", "path": "/spec/template/spec/containers/0/args/-", "value": "--feature-gates=TopologyAwareScheduling=true"}]'
   
3. Create a file named kueue-tas.yaml to configure the Kueue resources:
   apiVersion: kueue.x-k8s.io/v1beta2
   kind: Topology
   metadata:
     name: ib-topology
   spec:
     levels:
       - nodeLabel: "topology.nebius.com/gpu-cluster-id"
       - nodeLabel: "topology.nebius.com/tier-2"
       - nodeLabel: "topology.nebius.com/tier-1"
       - nodeLabel: "kubernetes.io/hostname"
   ---
   apiVersion: kueue.x-k8s.io/v1beta2
   kind: ResourceFlavor
   metadata:
     name: gpu-flavor-tas
   spec:
     nodeLabels:
       nebius.com/node-group-id: "<node_group_ID>"
     topologyName: "ib-topology"
     tolerations:
       - key: "nvidia.com/gpu"
         operator: "Exists"
         effect: "NoSchedule"
   ---
   apiVersion: kueue.x-k8s.io/v1beta2
   kind: ClusterQueue
   metadata:
     name: gpu-cluster-queue-tas
   spec:
     namespaceSelector: {}
     resourceGroups:
       - coveredResources: ["cpu", "memory", "nvidia.com/gpu"]
         flavors:
           - name: "gpu-flavor-tas"
             resources:
               - name: "cpu"
                 nominalQuota: 100
               - name: "memory"
                 nominalQuota: "100Gi"
               - name: "nvidia.com/gpu"
                 nominalQuota: "16"
   ---
   apiVersion: kueue.x-k8s.io/v1beta2
   kind: LocalQueue
   metadata:
     name: gpu-user-queue-tas
     namespace: default
   spec:
     clusterQueue: gpu-cluster-queue-tas
   
   To get the <node_group_ID>, open your Kubernetes cluster in the web console, go to the Node groups tab and copy the node group ID.
4. Apply the configuration:
   kubectl apply -f kueue-tas.yaml
   
5. Check that the Kueue resources were created:
   kubectl get topology,resourceflavor,clusterqueue,localqueue
   

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Schedule workloads with TAS using Kueue

1. Create a file named job-tas.yaml that requests TAS for the workload:
   apiVersion: batch/v1
   kind: Job
   metadata:
     name: job-tas
     namespace: default
     labels:
       kueue.x-k8s.io/queue-name: gpu-user-queue-tas
   spec:
     parallelism: <number_of_replicas>
     completions: <number_of_replicas>
     completionMode: Indexed
     template:
       metadata:
         annotations:
           <annotations_string>
       spec:
         containers:
         - name: dummy-job
           image: registry.k8s.io/e2e-test-images/agnhost:2.53
           args: ["pause"]
           resources:
             requests:
               cpu: "100m"
               memory: "100Mi"
               nvidia.com/gpu: 8
             limits:
               nvidia.com/gpu: 8
         restartPolicy: Never
   
   Replace the following variables:
   • <number_of_replicas>: Number of Pods that are running in parallel.
   • <annotations_string>: Requested topology constraint. See the following table for available values:

     Scenario	Description	Value of <annotations_string>
     Required to run within a GPU cluster	Kueue admits the workload only if enough resources are available within the same GPU cluster. Otherwise, the workload remains pending until resources become available or the topology constraint changes.	kueue.x-k8s.io/podset-required-topology: "topology.nebius.com/gpu-cluster-id"
     Required to run within a topology domain	Kueue admits the workload only if enough resources are available within the same topology domain. Otherwise, the workload remains pending until resources become available or the topology constraint changes.	kueue.x-k8s.io/podset-required-topology: "topology.nebius.com/tier-2"
     Preferred to run within a topology domain	Kueue tries to schedule Pods within the same topology domain. If this is not possible, Kueue can place Pods across multiple topology domains.	kueue.x-k8s.io/podset-preferred-topology: "topology.nebius.com/tier-2"

     In Kueue, a podset represents a group of Pods belonging to the same workload (for example, replicas of a Job).
2. Create the Job:
   kubectl apply -f job-tas.yaml
   
3. Check admission status:
   kubectl get workloads -A
   kubectl describe workload <workload_name> -n <namespace>
   
   If Kueue does not admit the workload, reduce parallelism, use less restrictive topology constraints or increase available GPU capacity.