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https://issues.apache.org/jira/browse/YARN-3136?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14349644#comment-14349644
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Jian He commented on YARN-3136:
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bq. Speaking of accessing the applications map without holding a proper lock,
doesn't AbstractYarnScheduler.createReleaseCache() do exactly that?
createReleaseCache is only called In serviceInit, so I think should be fine.
I have a general question that, is AbstractYarnScheduler supposed to be public
for external use ? I think AbstractYarnScheduler is just a common base class
so as to avoid code duplication among CS/Fair/Fifo schedulers. we'll most
likely add more changes in this class. IMHO, to not complicate things, we can
just mark AbstractYarnScheduler as Private/Unstable. this method was added a
year earlier and now will be invoked only if work-preserving-am-restart is
enabled. Maybe I'm wrong, I doubt we'll see compatibility issues in reality.
> 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
>
>
> 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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