Merge pull request #38471 from aireilly/gh#36355

gh#36355 - Clarify isolated and reserved CPUs information

Author: sagidlow

modules/configuring_hyperthreading_for_a_cluster.adoc

@@ -64,16 +64,21 @@ $ cat /sys/devices/system/cpu/cpu0/topology/thread_siblings_list
 0-4
 ----
 
-. Apply the isolated and reserved CPUs in the `PerformanceProfile` YAML. For example, you could set logical cores CPU0 and CPU4 as `isolated`, and logical cores CPU1 and CPU5 as `reserved`. When you configure reserved and isolated CPUs, the infra containers in pods use the reserved CPUs and the application containers use the isolated CPUs.
+. Apply the isolated and reserved CPUs in the `PerformanceProfile` YAML. For example, you can set logical cores CPU0 and CPU4 as `isolated`, and logical cores CPU1 to CPU3 and CPU5 to CPU7 as `reserved`. When you configure reserved and isolated CPUs, the infra containers in pods use the reserved CPUs and the application containers use the isolated CPUs.
 +
 [source,yaml]
 ----
 ...
   cpu:
-    isolated: 0-4
-    reserved: 1-5
+    isolated: 0,4
+    reserved: 1-3,5-7
 ...
 ----
++
+[NOTE]
+====
+The reserved and isolated CPU pools must not overlap and together must span all available cores in the worker node.
+====
 
 [IMPORTANT]
 ====