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https://issues.apache.org/jira/browse/HDFS-8046?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15329542#comment-15329542
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Kihwal Lee commented on HDFS-8046:
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[~xiaochen], thanks for letting me know. I've cherry-picked the fix to 2.6 and
2.7.
> Allow better control of getContentSummary
> -----------------------------------------
>
> Key: HDFS-8046
> URL: https://issues.apache.org/jira/browse/HDFS-8046
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Kihwal Lee
> Assignee: Kihwal Lee
> Labels: 2.6.1-candidate, 2.7.2-candidate
> Fix For: 2.6.1, 2.7.2
>
> Attachments: HDFS-8046-branch-2.6.1.txt, HDFS-8046.v1.patch
>
>
> On busy clusters, users performing quota checks against a big directory
> structure can affect the namenode performance. It has become a lot better
> after HDFS-4995, but as clusters get bigger and busier, it is apparent that
> we need finer grain control to avoid long read lock causing throughput drop.
> Even with unfair namesystem lock setting, a long read lock (10s of
> milliseconds) can starve many readers and especially writers. So the locking
> duration should be reduced, which can be done by imposing a lower
> count-per-iteration limit in the existing implementation. But HDFS-4995 came
> with a fixed amount of sleep between locks. This needs to be made
> configurable, so that {{getContentSummary()}} doesn't get exceedingly slow.
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