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https://issues.apache.org/jira/browse/YARN-6680?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16035337#comment-16035337
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Naganarasimha G R commented on YARN-6680:
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Thanks for the clarification [~daryn], my query was majorly related to see the
CPU profiler output based on which these modifications are done as earlier you
had just mentioned 3x performance decrease.
And good to hear that its already been reviewed by [~jlowe] and [~nroberts] ,
But just for my clarification could you help me in understanding following
points:
# IIUC , the RW locks of CommonNodeLabelsManager is same as in 2.7, so wonder
why the performance was impacted if you have migrated from 2.7.x to 2.8.
# ??Eventually these maps should be concurrent maps which uses no lock for read
ops, and the memory read barriers are cheap?? {{labelCollections}} and
{{nodeCollections}} are already concurrentmaps. so you meant RW locks are not
required?
# Assume we solve the issue for NO_LABEL but still the flow is same for other
labels. So issue will still be present with flows for other labels?
# did not quite get your consistent and Inconsistent example though agree that
the resource object got during read gets modified using the write lock as the
same resource object is being returned instead of a clone.
cc [~wangda]
> Avoid locking overhead for NO_LABEL lookups
> -------------------------------------------
>
> Key: YARN-6680
> URL: https://issues.apache.org/jira/browse/YARN-6680
> Project: Hadoop YARN
> Issue Type: Sub-task
> Components: resourcemanager
> Affects Versions: 2.8.0
> Reporter: Daryn Sharp
> Assignee: Daryn Sharp
> Attachments: YARN-6680.patch
>
>
> Labels are managed via a hash that is protected with a read lock. The lock
> acquire and release are each just as expensive as the hash lookup itself -
> resulting in a 3X slowdown.
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