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https://issues.apache.org/jira/browse/YARN-7149?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16157290#comment-16157290
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Wangda Tan commented on YARN-7149:
----------------------------------

[~eepayne], 
Yes you're correct, I checked the old logic:
https://github.com/apache/hadoop/blob/branch-2.7/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/capacity/LeafQueue.java:
{code}
    Resource limit =
        Resources.roundUp(
            resourceCalculator, 
            Resources.min(
                resourceCalculator, clusterResource,   
                Resources.max(
                    resourceCalculator, clusterResource, 
                    Resources.divideAndCeil(
                        resourceCalculator, currentCapacity, activeUsers),
                    Resources.divideAndCeil(
                        resourceCalculator, 
                        Resources.multiplyAndRoundDown(
                            currentCapacity, userLimit), 
                        100)
                    ), 
                Resources.multiplyAndRoundDown(queueCapacity, userLimitFactor)
                ), 
            minimumAllocation);
{code}

The {{max}} op is consistent with old behavior, we don't need to change it to 
{{min}}.

> Cross-queue preemption sometimes starves an underserved queue
> -------------------------------------------------------------
>
>                 Key: YARN-7149
>                 URL: https://issues.apache.org/jira/browse/YARN-7149
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: capacity scheduler
>    Affects Versions: 2.9.0, 3.0.0-alpha3
>            Reporter: Eric Payne
>            Assignee: Eric Payne
>         Attachments: YARN-7149.demo.unit-test.patch
>
>
> In branch 2 and trunk, I am consistently seeing some use cases where 
> cross-queue preemption does not happen when it should. I do not see this in 
> branch-2.8.
> Use Case:
> | | *Size* | *Minimum Container Size* |
> |MyCluster | 20 GB | 0.5 GB |
> | *Queue Name* | *Capacity* | *Absolute Capacity* | *Minimum User Limit 
> Percent (MULP)* | *User Limit Factor (ULF)* |
> |Q1 | 50% = 10 GB | 100% = 20 GB | 10% = 1 GB | 2.0 |
> |Q2 | 50% = 10 GB | 100% = 20 GB | 10% = 1 GB | 2.0 |
> - {{User1}} launches {{App1}} in {{Q1}} and consumes all resources (20 GB)
> - {{User2}} launches {{App2}} in {{Q2}} and requests 10 GB
> - _Note: containers are 0.5 GB._
> - Preemption monitor kills 2 containers (equals 1 GB) from {{App1}} in {{Q1}}.
> - Capacity Scheduler assigns 2 containers (equals 1 GB) to {{App2}} in {{Q2}}.
> - _No more containers are ever preempted, even though {{Q2}} is far 
> underserved_



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