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https://issues.apache.org/jira/browse/YARN-7149?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16157263#comment-16157263
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Eric Payne commented on YARN-7149:
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Thanks very much for your insights [~leftnoteasy].
bq. When we have two active users in the queue, and userLimit set to 100, first
user will always get preferred until queue reaches maxCapacity.
I assume {{userLimit}} means {{minimum-user-limit-percent}}, correct? If so,
then shouldn't the above statement be "first user will always get preferred
until queue reaches {{Capacity * user-limit-factor}}"? If my assumptions are
correct, then I think this is exactly the behavior we want. If a queue has a
MULP of 100%, then by-definition only the user with the first active app gets
resources. Can you please elaborate on this use case?
> 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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