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https://issues.apache.org/jira/browse/HDFS-9198?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15121517#comment-15121517
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Kihwal Lee commented on HDFS-9198:
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We have applied this internally to 2.7 and run for quite some time. So I would
say it is safe. HDFS-8999 and HDFS-9710 will make it less important, but since
these are more invasive and risky, HDFS-9198 in 2.7 might be a better
alternative for now.
> Coalesce IBR processing in the NN
> ---------------------------------
>
> Key: HDFS-9198
> URL: https://issues.apache.org/jira/browse/HDFS-9198
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode
> Affects Versions: 2.0.0-alpha
> Reporter: Daryn Sharp
> Assignee: Daryn Sharp
> Fix For: 2.8.0
>
> Attachments: HDFS-9198-Branch-2-withamend.diff,
> HDFS-9198-Branch-2.8-withamend.diff, HDFS-9198-branch2.patch,
> HDFS-9198-trunk.patch, HDFS-9198-trunk.patch, HDFS-9198-trunk.patch,
> HDFS-9198-trunk.patch, HDFS-9198-trunk.patch
>
>
> IBRs from thousands of DNs under load will degrade NN performance due to
> excessive write-lock contention from multiple IPC handler threads. The IBR
> processing is quick, so the lock contention may be reduced by coalescing
> multiple IBRs into a single write-lock transaction. The handlers will also
> be freed up faster for other operations.
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