Merge pull request #23317 from mburke5678/nodes-add-reserved-cpus

add --reserved-cpus kubelet command option

Author: mburke5678

_topic_map.yml

@@ -1563,6 +1563,8 @@ Topics:
     File: nodes-nodes-garbage-collection
   - Name: Allocating resources for nodes
     File: nodes-nodes-resources-configuring
+  - Name: Allocating specific CPUs for nodes in a cluster
+    File: nodes-nodes-resources-cpus
 #  - Name: Monitoring for problems in your nodes
 #    File: nodes-nodes-problem-detector
   - Name: Machine Config Daemon metrics

modules/nodes-nodes-resources-configuring-about.adoc

@@ -22,6 +22,11 @@ If a flag is not set, the defaults are used. If none of the flags are set, the
 allocated resource is set to the node's capacity as it was before the
 introduction of allocatable resources.
 
+[NOTE]
+====
+Any CPUs specifically reserved using the `reservedSystemCPUs` parameter are not available for allocation using `kube-reserved` or `system-reserved`.
+====
+
 [id="computing-allocated-resources_{context}"]
 == How {product-title} computes allocated resources
 

modules/nodes-nodes-resources-cpus-reserve.adoc

@@ -0,0 +1,65 @@
+// Module included in the following assemblies:
+//
+// * nodes/nodes-nodes-resources-cpus
+
+[id="nodes-nodes-resources-cpus-reserve_{context}"]
+= Reserving CPUs for nodes
+
+To explicitly define a list of CPUs that are reserved for specific nodes, create a `KubeletConfig` custom resource (CR) to define the `reservedSystemCPUs` parameter. This list supersedes the CPUs that might be reserved using the `systemReserved` and `kubeReserved` parameters.
+
+.Procedure
+
+. Obtain the label associated with the machine config pool (MCP) for the type of node you want to configure:
++
+[source,terminal]
+----
+$ oc describe machineconfigpool <name>
+----
++
+For example:
++
+[source,terminal]
+----
+$ oc describe machineconfigpool worker
+----
++
+.Example output
+[source,yaml]
+----
+Name:         worker
+Namespace:    
+Labels:       machineconfiguration.openshift.io/mco-built-in=
+              pools.operator.machineconfiguration.openshift.io/worker= <1>
+Annotations:  <none>
+API Version:  machineconfiguration.openshift.io/v1
+Kind:         MachineConfigPool
+...
+----
+<1> Get the MCP label. 
+
+. Create a YAML file for the `KubeletConfig` CR:
++
+[source,yaml]
+---- 
+apiVersion: machineconfiguration.openshift.io/v1
+kind: KubeletConfig
+metadata:
+  name: set-reserved-cpus <1>  
+spec:
+  kubeletConfig:
+    reservedSystemCPUs: "0,1,2,3" <2>
+  machineConfigPoolSelector:
+    matchLabels:
+      pools.operator.machineconfiguration.openshift.io/worker: "" <3>
+----
+<1> Specify a name for the CR.
+<2> Specify the core IDs of the CPUs you want to reserve for the nodes associated with the MCP.
+<3> Specify the label from the MCP.
+
+. Create the CR object:
++
+[source,terminal]
+----
+$ oc create -f <file_name>.yaml
+----
+

nodes/nodes/nodes-nodes-resources-cpus.adoc

@@ -0,0 +1,20 @@
+:context: nodes-nodes-resources-cpus
+[id="nodes-nodes-resources-cpus"]
+= Allocating specific CPUs for nodes in a cluster
+include::modules/common-attributes.adoc[]
+
+toc::[]
+
+
+When using the xref:../../scalability_and_performance/using-cpu-manager.adoc[static CPU Manager policy], you can reserve specific CPUs for use by specific nodes in your cluster. For example, on a system with 24 CPUs, you could reserve CPUs numbered 0 - 3 for the control plane allowing the compute nodes to use CPUs 4 - 23.
+
+// The following include statements pull in the module files that comprise
+// the assembly. Include any combination of concept, procedure, or reference
+// modules required to cover the user story. You can also include other
+// assemblies.
+
+include::modules/nodes-nodes-resources-cpus-reserve.adoc[leveloffset=+1]
+
+.Additional resources
+
+* For more information on the `systemReserved` and `kubeReserved` parameters, see xref:../../nodes/nodes/nodes-nodes-resources-configuring.html#nodes-nodes-resources-configuring-about_nodes-nodes-resources-configuring[Allocating resources for nodes in an {product-title} cluster].