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https://issues.apache.org/jira/browse/YARN-6538?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16773177#comment-16773177
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Eric Payne commented on YARN-6538:
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In practice, this seems to me to be an uncommon use case. For example, in our
clusters, we have an average of about 7 vcores per gigabyte, and we use
preemption all the time. In the above example, there is 0.05 vcores per
gigabyte. This seems like a fringe case where preemption may not be happening
because of rounding calculations.
> Inter Queue preemption is not happening when DRF is configured
> --------------------------------------------------------------
>
> Key: YARN-6538
> URL: https://issues.apache.org/jira/browse/YARN-6538
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: capacity scheduler, scheduler preemption
> Affects Versions: 2.8.0
> Reporter: Sunil Govindan
> Assignee: Sunil Govindan
> Priority: Major
>
> Cluster capacity of <memory:3TB, vCores:168>. Here memory is more and vcores
> are less. If applications have more demand, vcores might be exhausted.
> Inter queue preemption ideally has to be kicked in once vcores is over
> utilized. However preemption is not happening.
> Analysis:
> In {{AbstractPreemptableResourceCalculator.computeFixpointAllocation}},
> {code}
> // assign all cluster resources until no more demand, or no resources are
> // left
> while (!orderedByNeed.isEmpty() && Resources.greaterThan(rc, totGuarant,
> unassigned, Resources.none())) {
> {code}
> will loop even when vcores are 0 (because memory is still +ve). Hence we are
> having more vcores in idealAssigned which cause no-preemption cases.
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