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From "Eric Payne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-4945) [Umbrella] Capacity Scheduler Preemption Within a queue
Date Mon, 05 Sep 2016 18:58:21 GMT

    [ https://issues.apache.org/jira/browse/YARN-4945?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15465592#comment-15465592

Eric Payne commented on YARN-4945:

[~leftnoteasy] and [~sunilg],
bq. Using logic similar to {{deductPreemptableResourcesBasedSelectedCandidates}} should be
able to achieve this, and I think it doesn't bring too many complexities to the implementation.
I'm sorry, but I'm still not understanding how this can work.

In {{PriorityCandidatesSelector#preemptFromLeastStarvedApp}}:
      if (CapacitySchedulerPreemptionUtils.isContainerAlreadySelected(c,
          selectedCandidates)) {
        Resources.subtractFrom(toObtainByPartition, c.getAllocatedResource());
        Resources.subtractFrom(toObtainByPartition, c.getAllocatedResource());
This code seems to indicate that if a container is already in {{selectedCandidates}}, it will
be preempted and then given back to apps in this queue. But if it's already in {{selectedCandidates}},
it's because an inter-queue preemption policy put it there, so it's not likely to end up back
in this queue. Please help me understand what I'm missing.

Also, Why is it subtracting the container's resources twice from {{toObtainByPartition}}?
Should one of those be {{totalPreemptedResourceAllowed}}?

> [Umbrella] Capacity Scheduler Preemption Within a queue
> -------------------------------------------------------
>                 Key: YARN-4945
>                 URL: https://issues.apache.org/jira/browse/YARN-4945
>             Project: Hadoop YARN
>          Issue Type: Bug
>            Reporter: Wangda Tan
>         Attachments: Intra-Queue Preemption Use Cases.pdf, IntraQueuepreemption-CapacityScheduler
(Design).pdf, YARN-2009-wip.2.patch, YARN-2009-wip.patch
> This is umbrella ticket to track efforts of preemption within a queue to support features
> YARN-2009. YARN-2113. YARN-4781.

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