From f5524153ba5be7f2988bf5f0f80efe98737f42e8 Mon Sep 17 00:00:00 2001
From: lixiang <lixiang.cdc@gmail.com>
Date: Tue, 4 Aug 2020 11:11:40 +0800
Subject: [PATCH] README: add description for priority threshold

---
 README.md | 39 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 69ea8fe6d..4c0e3a585 100644
--- a/README.md
+++ b/README.md
@@ -234,7 +234,9 @@ strategies:
         maxPodLifeTimeSeconds: 86400
 ````
 
-## Namespace filtering
+## Filter Pods
+
+### Namespace filtering
 
 Strategies like `PodLifeTime`, `RemovePodsHavingTooManyRestarts`, `RemovePodsViolatingNodeTaints`,
 `RemovePodsViolatingNodeAffinity` and `RemovePodsViolatingInterPodAntiAffinity` can specify `namespaces`
@@ -276,6 +278,41 @@ The strategy gets executed over all namespaces but `namespace1` and `namespace2`
 
 It's not allowed to compute `include` with `exclude` field.
 
+### Priority filtering
+
+All strategies are able to configure a priority threshold, only pods under the threshold can be evicted. You can
+specify this threshold by setting `thresholdPriorityClassName`(setting the threshold to the value of the given
+priority class) or `thresholdPriority`(directly setting the threshold) parameters. By default, this threshold
+is set to the value of `system-cluster-critical` priority class.
+E.g.
+
+Setting `thresholdPriority`
+```
+apiVersion: "descheduler/v1alpha1"
+kind: "DeschedulerPolicy"
+strategies:
+  "PodLifeTime":
+     enabled: true
+     params:
+        maxPodLifeTimeSeconds: 86400
+        thresholdPriority: 10000
+```
+
+Setting `thresholdPriorityClassName`
+```
+apiVersion: "descheduler/v1alpha1"
+kind: "DeschedulerPolicy"
+strategies:
+  "PodLifeTime":
+     enabled: true
+     params:
+        maxPodLifeTimeSeconds: 86400
+        thresholdPriorityClassName: "priorityclass1"
+```
+
+Note that you can't configure both `thresholdPriority` and `thresholdPriorityClassName`, if the given priority class
+does not exist, descheduler won't create it and will throw an error.
+
 ## Pod Evictions
 
 When the descheduler decides to evict pods from a node, it employs the following general mechanism: