advanced-node-tuning-hosted-cluster.adoc

Advanced node tuning for hosted clusters by setting kernel boot parameters

snippets/technology-preview.adoc

For more advanced tuning in hosted control planes, which requires setting kernel boot parameters, you can also use the Node Tuning Operator. The following example shows how you can create a node pool with huge pages reserved.

Procedure

1. Create a ConfigMap object that contains a Tuned object manifest for creating 10 huge pages that are 2 MB in size. Save this ConfigMap manifest in a file named tuned-hugepages.yaml:

       apiVersion: v1
       kind: ConfigMap
       metadata:
         name: tuned-hugepages
         namespace: clusters
       data:
         tuning: |
           apiVersion: tuned.openshift.io/v1
           kind: Tuned
           metadata:
             name: hugepages
             namespace: openshift-cluster-node-tuning-operator
           spec:
             profile:
             - data: |
                 [main]
                 summary=Boot time configuration for hugepages
                 include=openshift-node
                 [bootloader]
                 cmdline_openshift_node_hugepages=hugepagesz=2M hugepages=50
               name: openshift-node-hugepages
             recommend:
             - priority: 20
               profile: openshift-node-hugepages

   Note

   The .spec.recommend.match field is intentionally left blank. In this case, this Tuned object is applied to all nodes in the node pool where this ConfigMap object is referenced. Group nodes with the same hardware configuration into the same node pool. Otherwise, TuneD operands can calculate conflicting kernel parameters for two or more nodes that share the same node pool.

2. Create the ConfigMap object in the management cluster:

   $ oc --kubeconfig="$MGMT_KUBECONFIG" create -f tuned-hugepages.yaml

3. Create a NodePool manifest YAML file, customize the upgrade type of the NodePool, and reference the ConfigMap object that you created in the spec.tuningConfig section. Create the NodePool manifest and save it in a file named hugepages-nodepool.yaml by using the hypershift CLI:

       NODEPOOL_NAME=hugepages-example
       INSTANCE_TYPE=m5.2xlarge
       NODEPOOL_REPLICAS=2
   
       hypershift create nodepool aws \
         --cluster-name $CLUSTER_NAME \
         --name $NODEPOOL_NAME \
         --node-count $NODEPOOL_REPLICAS \
         --instance-type $INSTANCE_TYPE \
         --render > hugepages-nodepool.yaml

4. In the hugepages-nodepool.yaml file, set .spec.management.upgradeType to InPlace, and set .spec.tuningConfig to reference the tuned-hugepages ConfigMap object that you created.

       apiVersion: hypershift.openshift.io/v1alpha1
       kind: NodePool
       metadata:
         name: hugepages-nodepool
         namespace: clusters
         ...
       spec:
         management:
           ...
           upgradeType: InPlace
         ...
         tuningConfig:
         - name: tuned-hugepages

   Note

   To avoid the unnecessary re-creation of nodes when you apply the new MachineConfig objects, set .spec.management.upgradeType to InPlace. If you use the Replace upgrade type, nodes are fully deleted and new nodes can replace them when you apply the new kernel boot parameters that the TuneD operand calculated.

5. Create the NodePool in the management cluster:

   $ oc --kubeconfig="$MGMT_KUBECONFIG" create -f hugepages-nodepool.yaml

Verification

After the nodes are available, the containerized TuneD daemon calculates the required kernel boot parameters based on the applied TuneD profile. After the nodes are ready and reboot once to apply the generated MachineConfig object, you can verify that the TuneD profile is applied and that the kernel boot parameters are set.

1. List the Tuned objects in the hosted cluster:

   $ oc --kubeconfig="$HC_KUBECONFIG" get Tuneds -n openshift-cluster-node-tuning-operator

   Example output

   NAME                 AGE
   default              123m
   hugepages-8dfb1fed   1m23s
   rendered             123m

2. List the Profile objects in the hosted cluster:

   $ oc --kubeconfig="$HC_KUBECONFIG" get Profiles -n openshift-cluster-node-tuning-operator

   Example output

   NAME                           TUNED                      APPLIED   DEGRADED   AGE
   nodepool-1-worker-1            openshift-node             True      False      132m
   nodepool-1-worker-2            openshift-node             True      False      131m
   hugepages-nodepool-worker-1    openshift-node-hugepages   True      False      4m8s
   hugepages-nodepool-worker-2    openshift-node-hugepages   True      False      3m57s

   Both of the worker nodes in the new NodePool have the openshift-node-hugepages profile applied.

3. To confirm that the tuning was applied correctly, start a debug shell on a node and check /proc/cmdline.

   $ oc --kubeconfig="$HC_KUBECONFIG" debug node/nodepool-1-worker-1 -- chroot /host cat /proc/cmdline

   Example output

   BOOT_IMAGE=(hd0,gpt3)/ostree/rhcos-... hugepagesz=2M hugepages=50