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