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From "Sandy Ryza (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-596) In fair scheduler, intra-application container priorities affect inter-application preemption decisions
Date Tue, 08 Apr 2014 18:23:17 GMT

    [ https://issues.apache.org/jira/browse/YARN-596?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13963271#comment-13963271
] 

Sandy Ryza commented on YARN-596:
---------------------------------

bq. Sandy Ryza, so here the ''safe'' means "usage.memory > fairshare.memory and usage.vcores
> fairshare.vcores"? 
Right, but with those ">"s as "<="s.

bq. But the fairshare.vcores for FSQueue (except root) is always 0. And fairscheduler only
considers memory when do scheduling, so do we still need to consider vcores here?
These are only the case when the FairSharePolicy is used.  When the DominantResourceFairnessPolicy
is used, the vcores fair share is greater than 0 and the Fair Scheduler considers both memory
and vcores for scheduling.

> In fair scheduler, intra-application container priorities affect inter-application preemption
decisions
> -------------------------------------------------------------------------------------------------------
>
>                 Key: YARN-596
>                 URL: https://issues.apache.org/jira/browse/YARN-596
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: scheduler
>    Affects Versions: 2.0.3-alpha
>            Reporter: Sandy Ryza
>            Assignee: Sandy Ryza
>         Attachments: YARN-596.patch, YARN-596.patch, YARN-596.patch, YARN-596.patch,
YARN-596.patch
>
>
> In the fair scheduler, containers are chosen for preemption in the following way:
> All containers for all apps that are in queues that are over their fair share are put
in a list.
> The list is sorted in order of the priority that the container was requested in.
> This means that an application can shield itself from preemption by requesting it's containers
at higher priorities, which doesn't really make sense.
> Also, an application that is not over its fair share, but that is in a queue that is
over it's fair share is just as likely to have containers preempted as an application that
is over its fair share.



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