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From "Eric Payne (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-4390) Consider container request size during CS preemption
Date Fri, 22 Apr 2016 13:06:12 GMT

    [ https://issues.apache.org/jira/browse/YARN-4390?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15253884#comment-15253884
] 

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

{quote}
And since it uses R/W lock, write lock will be acquired only if node add / move or node resource
update. So in most cases, nobody acquires write lock. I agree to cache node list inside PCPP
if we do see performance issues.
{quote}
[~leftnoteasy], yes, that is a very good point. I was not thinking about {{ClusterNodeTracker#getNodes}}
using the read lock, which, of course, can have multiple readers at any time. After thinking
more about it, I don't think this will cause much of a strain on the RM.

I still want to experiment with the patch a little more.

> Consider container request size during CS preemption
> ----------------------------------------------------
>
>                 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: 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
>
>
> 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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