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https://issues.apache.org/jira/browse/HDFS-11615?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15965062#comment-15965062
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Andrew Wang commented on HDFS-11615:
------------------------------------

These metrics are normally consumed by a metrics system and regraphed, so I 
don't think human parsing is that important.

Related note, I like to put the unit (e.g. "Nanos") into the metric and 
variable name, since otherwise I have to look it up each time. Possible to do 
this here too?

> 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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