[jira] [Commented] (YARN-4120) FSAppAttempt.getResourceUsage() should not take preemptedResource into account

["Karthik Kambatla (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/YARN-4120?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14732394#comment-14732394 ] 

Karthik Kambatla commented on YARN-4120:
----------------------------------------

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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