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https://issues.apache.org/jira/browse/YARN-4390?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15261207#comment-15261207
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Wangda Tan commented on YARN-4390:
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Oh, I think I understand what happened.
If you set nature_termination_factor to < 1, AM cannot be reserved in some
cases because of YARN-4280. (Reserving AM needs 2G resources, but every time
preemption policy only preempts one container which goes back to original
queue.).
So set it to 1 is still needed.
> Do surgical preemption based on reserved container in CapacityScheduler
> -----------------------------------------------------------------------
>
> Key: YARN-4390
> URL: https://issues.apache.org/jira/browse/YARN-4390
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: capacity scheduler
> Affects Versions: 3.0.0, 2.8.0, 2.7.3
> Reporter: Eric Payne
> Assignee: Wangda Tan
> Attachments: QueueNotHittingMax.jpg, YARN-4390-design.1.pdf,
> YARN-4390-test-results.pdf, YARN-4390.1.patch, YARN-4390.2.patch,
> YARN-4390.3.branch-2.patch, YARN-4390.3.patch, YARN-4390.4.patch,
> YARN-4390.5.patch, YARN-4390.6.patch, YARN-4390.7.patch
>
>
> There are multiple reasons why preemption could unnecessarily preempt
> containers. One is that an app could be requesting a large container (say
> 8-GB), and the preemption monitor could conceivably preempt multiple
> containers (say 8, 1-GB containers) in order to fill the large container
> request. These smaller containers would then be rejected by the requesting AM
> and potentially given right back to the preempted app.
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