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https://issues.apache.org/jira/browse/YARN-6151?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15856921#comment-15856921
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ASF GitHub Bot commented on YARN-6151:
--------------------------------------
Github user flyrain commented on a diff in the pull request:
https://github.com/apache/hadoop/pull/188#discussion_r99944929
--- Diff:
hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/FSQueue.java
---
@@ -236,6 +236,29 @@ public void setFairSharePreemptionThreshold(float
fairSharePreemptionThreshold)
}
/**
+ * Recursively check if the queue can be preempted based on whether the
+ * resource usage is greater than fair share.
+ *
+ * @return true if the queue can be preempted
+ */
+ public boolean canBePreempted() {
--- End diff --
It should be, but allowPreemptionFrom is introduced after 2.8.x.
> FS Preemption doesn't filter out queues which cannot be preempted
> -----------------------------------------------------------------
>
> Key: YARN-6151
> URL: https://issues.apache.org/jira/browse/YARN-6151
> Project: Hadoop YARN
> Issue Type: Bug
> Components: fairscheduler
> Affects Versions: 2.8.0
> Reporter: Yufei Gu
> Assignee: Yufei Gu
> Attachments: YARN-6151.branch-2.8.001.patch
>
>
> This is preemption bug happens before 2.8.0, which also described in
> YARN-3405.
> Queue hierarchy described as below:
> {noformat}
> root
> / \
> queue-1 queue-2
> / \
> queue-1-1 queue-1-2
> {noformat}
> Assume cluster resource is 100 and all queues have same weights.
> # queue-1-1 and queue-2 has apps. Each get 50 usage and 50 fairshare.
> # When queue-1-2 is active, supposedly it will preempt 25 from queue-1-1, but
> this doesn't happen because preemption happens top-down, queue-2 could be the
> preemption candidate as long as queue-2 is less needy than queue-1, and
> queue-2 doesn't exceed the fair share which means preemption won't happen.
> We need to filter out queue-2 since it isn't a valid candidate.
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