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https://issues.apache.org/jira/browse/YARN-4390?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15025542#comment-15025542
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Bikas Saha commented on YARN-4390:
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I am not sure if this is a bug as described. If preemption does free 8x1GB
containers then it will create 8GB free space on the node. The scheduler (which
is container request size aware) should then allocate 1x8GB container to the
under-allocated AM. [~curino] Is that correct? Of course there could be a bug
in the implementation but by design, this should not happening.
However, if YARN ends up preempting 8x1GB containers on different nodes then
the under-allocated AM will not get its resources and may result in further
avoidable preemptions. This is [~sunilg] case.
> Consider container request size during CS preemption
> ----------------------------------------------------
>
> Key: YARN-4390
> URL: https://issues.apache.org/jira/browse/YARN-4390
> Project: Hadoop YARN
> Issue Type: Bug
> Components: capacity scheduler
> Affects Versions: 3.0.0, 2.8.0, 2.7.3
> Reporter: Eric Payne
> Assignee: Eric Payne
>
> 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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