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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-6151) FS Preemption doesn't filter out queues which cannot be preempted
Date Tue, 07 Feb 2017 22:14:42 GMT

    [ https://issues.apache.org/jira/browse/YARN-6151?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15856916#comment-15856916
] 

ASF GitHub Bot commented on YARN-6151:
--------------------------------------

Github user kambatla commented on a diff in the pull request:

    https://github.com/apache/hadoop/pull/188#discussion_r99943676
  
    --- 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 --
    
    Should the check of the allowPreemptionFrom flag also be part of this method? 


> 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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