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https://issues.apache.org/jira/browse/YARN-4120?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14732394#comment-14732394
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Karthik Kambatla commented on YARN-4120:
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Good catch, [~xinxianyin].
I believe the reason we are subtracting preempted resources is so we don't
preempt more resources from the same queue. We might have to track that
information separately. [~asuresh], [~ashwinshankar77] - thoughts?
> FSAppAttempt.getResourceUsage() should not take preemptedResource into account
> ------------------------------------------------------------------------------
>
> Key: YARN-4120
> URL: https://issues.apache.org/jira/browse/YARN-4120
> Project: Hadoop YARN
> Issue Type: Bug
> Components: fairscheduler
> Reporter: Xianyin Xin
>
> When compute resource usage for Schedulables, the following code is envolved,
> {{FSAppAttempt.getResourceUsage}},
> {code}
> public Resource getResourceUsage() {
> return Resources.subtract(getCurrentConsumption(), getPreemptedResources());
> }
> {code}
> and this value is aggregated to FSLeafQueues and FSParentQueues. In my
> opinion, taking {{preemptedResource}} into account here is not reasonable,
> there are two main reasons,
> # it is something in future, i.e., even though these resources are marked as
> preempted, it is currently used by app, and these resources will be
> subtracted from {{currentCosumption}} once the preemption is finished. it's
> not reasonable to make arrange for it ahead of time.
> # there's another problem here, consider following case,
> {code}
> root
> / \
> queue1 queue2
> / \
> queue1.3, queue1.4
> {code}
> suppose queue1.3 need resource and it can preempt resources from queue1.4,
> the preemption happens in the interior of queue1. But when compute resource
> usage of queue1, {{queue1.resourceUsage = it's_current_resource_usage -
> preemption}} according to the current code, which is unfair to queue2 when
> doing resource allocating.
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