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Date: Mon, 30 Mar 2015 18:12:02 +0000 (UTC)
From: "Sunil G (JIRA)" <jira@apache.org>
To: yarn-issues@hadoop.apache.org
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Subject: [jira] [Commented] (YARN-3136) getTransferredContainers can be a
 bottleneck during AM registration
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    [ https://issues.apache.org/jira/browse/YARN-3136?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14387114#comment-14387114 ] 

Sunil G commented on YARN-3136:
-------------------------------

Hi [~jlowe] [~jianhe]
{noformat}
Bug type IS2_INCONSISTENT_SYNC (click for details) 
In class org.apache.hadoop.yarn.server.resourcemanager.scheduler.AbstractYarnScheduler
Field org.apache.hadoop.yarn.server.resourcemanager.scheduler.AbstractYarnScheduler.applications
Synchronized 90% of the time
Unsynchronized access at AbstractYarnScheduler.java:[line 138]
Unsynchronized access at AbstractYarnScheduler.java:[line 165]
Unsynchronized access at AbstractYarnScheduler.java:[line 233]
{noformat}

As "applications" is now a concurrent version, I feel we do not need a lock. Kindly share your opinion.

test case failure is not related.


> 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, 0002-YARN-3136.patch, 0003-YARN-3136.patch, 0004-YARN-3136.patch, 0005-YARN-3136.patch, 0006-YARN-3136.patch, 0007-YARN-3136.patch, 0008-YARN-3136.patch, 0009-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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