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https://issues.apache.org/jira/browse/YARN-1957?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13983978#comment-13983978
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Chris Douglas commented on YARN-1957:
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+1
Enforcing {{maxCapacity}} in the calculation of the ideal capacity is a good
fix, and distributing capacity over queues with zero capacity (with the config
knob to restore the existing 0 == disabled with aggressive preemption) makes
sense. The code appears to effect this, also. There's a slight optimization
that can separate the zero-capacity queues during cloning, but the overhead is
negligible.
> ProportionalCapacitPreemptionPolicy handling of corner cases...
> ---------------------------------------------------------------
>
> Key: YARN-1957
> URL: https://issues.apache.org/jira/browse/YARN-1957
> Project: Hadoop YARN
> Issue Type: Bug
> Components: resourcemanager
> Affects Versions: 2.4.0
> Reporter: Carlo Curino
> Assignee: Carlo Curino
> Labels: capacity-scheduler, preemption
> Attachments: YARN-1957.patch, YARN-1957.patch, YARN-1957_test.patch
>
>
> The current version of ProportionalCapacityPreemptionPolicy should be
> improved to deal with the following two scenarios:
> 1) when rebalancing over-capacity allocations, it potentially preempts
> without considering the maxCapacity constraints of a queue (i.e., preempting
> possibly more than strictly necessary)
> 2) a zero capacity queue is preempted even if there is no demand (coherent
> with old use of zero-capacity to disabled queues)
> The proposed patch fixes both issues, and introduce few new test cases.
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