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https://issues.apache.org/jira/browse/YARN-6361?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Yufei Gu updated YARN-6361:
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    Description: FSLeafQueue.fetchAppsWithDemand sorts the applications by the 
current policy. Most of the time is spent in FairShareComparator.compare. We 
could improve this by doing the calculations outside the sort loop {{(O\(n\))}} 
and we sorted by a fixed number inside instead {{O(n*log\(n\))}}. This could be 
an performance issue when there are huge number of applications in a single 
queue. The attachments shows the performance impact when there are 10k 
applications in one queue.  (was: FSLeafQueue.fetchAppsWithDemand sorts the 
applications by the current policy. Most of the time is spent in 
FairShareComparator.compare. We could improve this by doing the calculations 
outside the sort loop {{(O\(n\))}} and we sorted by a fixed number inside 
instead {{O(n*log\(n\))}}.)

> FairScheduler: FSLeafQueue.fetchAppsWithDemand CPU usage is high with big 
> queues
> --------------------------------------------------------------------------------
>
>                 Key: YARN-6361
>                 URL: https://issues.apache.org/jira/browse/YARN-6361
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>            Reporter: Miklos Szegedi
>            Assignee: Yufei Gu
>            Priority: Minor
>         Attachments: dispatcherthread.png, threads.png
>
>
> FSLeafQueue.fetchAppsWithDemand sorts the applications by the current policy. 
> Most of the time is spent in FairShareComparator.compare. We could improve 
> this by doing the calculations outside the sort loop {{(O\(n\))}} and we 
> sorted by a fixed number inside instead {{O(n*log\(n\))}}. This could be an 
> performance issue when there are huge number of applications in a single 
> queue. The attachments shows the performance impact when there are 10k 
> applications in one queue.



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