Added explanation of non-preempting PriorityClasses to the "Pod Prior…

…ity and Preemption" doc.

content/en/docs/concepts/configuration/pod-priority-preemption.md

@@ -77,6 +77,12 @@ when a cluster is under resource pressure. For this reason, it is not
 recommended to disable preemption.
 {{< /note >}}
 
+{{< note >}}
+In Kubernetes 1.15 and later,
+PriorityClasses have the option to set `preemptionPolicy: Never`.
+This will prevent pods of that PriorityClass from preempting other pods.
+{{< /note >}}
+
 In Kubernetes 1.11 and later, preemption is controlled by a kube-scheduler flag
 `disablePreemption`, which is set to `false` by default.
 If you want to disable preemption despite the above note, you can set
@@ -145,6 +151,37 @@ globalDefault: false
 description: "This priority class should be used for XYZ service pods only."
 ```
 
+### Non-preempting PriorityClasses (alpha)
+
+In 1.15,
+PriorityClasses gain a non-preempting option,
+via the new `PreemptionPolicy` field.
+`PreemptionPolicy` defaults to `PreemptLowerPriority`.
+If `PreemptionPolicy` is set to `Never`,
+preemption will be disabled for pods of that PriorityClass.
+
+A PriorityClass with preempting disabled will still be scheduled based on its
+relative priority,
+but will not preempt other pods.
+Non-preempting PriorityClasses may still be preempted themselves.
+
+An example use case is for data science workloads.
+A user may submit a job that they want to be prioritized above other workloads,
+but do not wish to discard existing work by preempting running pods.
+
+#### Example Non-preempting PriorityClass
+
+```yaml
+apiVersion: scheduling.k8s.io/v1
+kind: PriorityClass
+metadata:
+  name: high-priority-nonpreempting
+value: 1000000
+preemptionPolicy: Never
+globalDefault: false
+description: "This priority class will not cause other pods to be preempted."
+```
+
 ## Pod priority
 
 After you have one or more PriorityClasses, you can create Pods that specify one