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https://issues.apache.org/jira/browse/YARN-3405?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14492467#comment-14492467
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Peng Zhang commented on YARN-3405:
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Other issues for preemption during development, need confirmation:
# Jobs in the same queue will not trigger preemption, cause resToPreemption()
only considers unfair between queues.
# MapReduce's map task will cause unneeded preemption request, because
FSAppAttempt.updateDemand() will count all of ANY, rack and host request, so
preemption demand will be triple for one map task. I want to change it to only
counting for ANY request, but do not know whether it will affect Non-MapReduce
framework.
# Notion of "MinResources" is confusing and easy to misconfigure. Because
calculation of fair share considers min, max & weight, when min of one queue is
above cluster resources or its parent queue, other queue's fair share is 0,
also I found sometimes sum of children's fair share can be larger than parent
queue's fair share. I have some suggestions for these notion like below:
* max resources means maximum resources that one queue can get
* min resources means under which threshold the queue cannot not be preempted
* weight notion changed to "expected fair share" - like <10240mb 10cores> (I
see weight implementation has memory and cpu, but we use only memory now), and
make "expected fair share" as the only considered element during calculation of
fair share.
> FairScheduler's preemption cannot happen between sibling in some case
> ---------------------------------------------------------------------
>
> Key: YARN-3405
> URL: https://issues.apache.org/jira/browse/YARN-3405
> Project: Hadoop YARN
> Issue Type: Bug
> Components: fairscheduler
> Affects Versions: 2.7.0
> Reporter: Peng Zhang
> Assignee: Peng Zhang
> Priority: Critical
> Attachments: YARN-3405.01.patch
>
>
> Queue hierarchy described as below:
> {noformat}
> root
> / \
> queue-1 queue-2
> / \
> queue-1-1 queue-1-2
> {noformat}
> Assume cluster resource is 100
> # queue-1-1 and queue-2 has app. Each get 50 usage and 50 fairshare.
> # When queue-1-2 is active, and it cause some new preemption request for
> fairshare 25.
> # When preemption from root, it has possibility to find preemption candidate
> is queue-2. If so preemptContainerPreCheck for queue-2 return false because
> it's equal to its fairshare.
> # Finally queue-1-2 will be waiting for resource release form queue-1-1
> itself.
> What I expect here is that queue-1-2 preempt from queue-1-1.
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