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From "Sunil G (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-3136) getTransferredContainers can be a bottleneck during AM registration
Date Thu, 05 Feb 2015 15:20:35 GMT

    [ https://issues.apache.org/jira/browse/YARN-3136?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14307377#comment-14307377
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Sunil G commented on YARN-3136:
-------------------------------

Hi [~jlowe]
Yes. I also had a concern on same, hence was planning for scheduler level lock to get object
from *applications* map.

FiFoScheduler is initializing with *ConcurrentSkipListMap*, CS and Fair Scheduler are using
*ConcurrentHashMap*.
So if we can have *applications* as *ConcurrentMap*, it looks fine. This does enforce other
pluggable schedulers to keep *applications* as a concurrentmap. Also this will break any such
schedulers which are present now once this change is made.

> getTransferredContainers can be a bottleneck during AM registration
> -------------------------------------------------------------------
>
>                 Key: YARN-3136
>                 URL: https://issues.apache.org/jira/browse/YARN-3136
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: scheduler
>    Affects Versions: 2.6.0
>            Reporter: Jason Lowe
>            Assignee: Sunil G
>         Attachments: 0001-YARN-3136.patch
>
>
> While examining RM stack traces on a busy cluster I noticed a pattern of AMs stuck waiting
for the scheduler lock trying to call getTransferredContainers.  The scheduler lock is highly
contended, especially on a large cluster with many nodes heartbeating, and it would be nice
if we could find a way to eliminate the need to grab this lock during this call.  We've already
done similar work during AM allocate calls to make sure they don't needlessly grab the scheduler
lock, and it would be good to do so here as well, if possible.



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