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https://issues.apache.org/jira/browse/YARN-3136?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14350654#comment-14350654
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Jian He commented on YARN-3136:
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bq. But createReleaseCache schedules a timer task that
Ah, yes, you are right. I missed the part that it's on a timer. thanks for
pointing out !
bq. the simplest thing to do here is to just document (or require, by changing
the type from Map to ConcurrentMap as I originally suggested) that the
underlying map must support concurrent access.
I agree.
> 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
>
>
> 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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