Merge pull request #90616 from rohennes/TELCODOCS-2127-follow-up

TELCODOCS-2127: Follow up PR to add limitation about real-time kernel

Author: skopacz1

modules/configuring-kernal-page-size.adoc

@@ -10,7 +10,9 @@ Use the `kernelPageSize` specification in a performance profile to configure the
 
 [NOTE]
 ====
-For nodes with an x86_64 or AMD64 architecture, you can only specify `4k` for the `kernelPageSize` specification. For nodes with an AArch64 architecture, you can specify `4k` or `64k` for the `kernelPageSize` specification. The default value is `4k`.
+For nodes with an x86_64 or AMD64 architecture, you can only specify `4k` for the `kernelPageSize` specification. 
+For nodes with an AArch64 architecture, you can specify `4k` or `64k` for the `kernelPageSize` specification. You must disable the realtime kernel before you can use the `64k` option. 
+The default value is `4k`.
 ====
 
 .Prerequisites
@@ -33,11 +35,14 @@ metadata:
 #...
 spec:
     kernelPageSize: "64k" <1>
+    realTimeKernel:
+        enabled: false <2>
     nodeSelector:
-        node-role.kubernetes.io/worker: "" <2>
+        node-role.kubernetes.io/worker: "" <3>
 ----
 <1> This example specifies a kernel page size of `64k`. You can only specify `64k` for nodes with an AArch64 architecture. The default value is `4k`.
-<2> This example targets nodes with the `worker` role.
+<2> You must disable the realtime kernel to use the `64k` kernel page size option.
+<3> This example targets nodes with the `worker` role.
 
 . Apply the performance profile to the cluster:
 +