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From "Eric Payne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-4390) Do surgical preemption based on reserved container in CapacityScheduler
Date Fri, 29 Apr 2016 16:03:12 GMT

    [ https://issues.apache.org/jira/browse/YARN-4390?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15264250#comment-15264250
] 

Eric Payne commented on YARN-4390:
----------------------------------

[~jlowe] pointed out to me offline that it is probably not reserving because of YARN-4280.
The app can't reserve the 1GB container because there is only 0.5GB left, so {{ReservedContainerCandidatesSelector#selectCandidates}}
isn't able to select any containers. Then, {{FifoCandidatesSelector#selectCandidates}} isn't
very smart and sees that if it marks any random 0.5GB container as preemptable, that plus
the free space equals the 1GB that is being requested.

> 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, YARN-4390.8.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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