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https://issues.apache.org/jira/browse/HDFS-11615?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15963454#comment-15963454
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Andrew Wang commented on HDFS-11615:
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If we have nanosecond precision, is there a reason to use microsecond rather
than nanosecond precision?
> FSNamesystemLock metrics can be inaccurate due to millisecond precision
> -----------------------------------------------------------------------
>
> Key: HDFS-11615
> URL: https://issues.apache.org/jira/browse/HDFS-11615
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: hdfs
> Affects Versions: 2.7.4
> Reporter: Erik Krogen
> Assignee: Erik Krogen
> Attachments: HDFS-11615.000.patch
>
>
> Currently the {{FSNamesystemLock}} metrics created in HDFS-10872 track the
> lock hold time using {{Timer.monotonicNow()}}, which has millisecond-level
> precision. However, many of these operations hold the lock for less than a
> millisecond, making these metrics inaccurate. We should instead use
> {{System.nanoTime()}} for higher accuracy.
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