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https://issues.apache.org/jira/browse/HDFS-16209?focusedWorklogId=647723&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-647723
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ASF GitHub Bot logged work on HDFS-16209:
-----------------------------------------

                Author: ASF GitHub Bot
            Created on: 08/Sep/21 04:39
            Start Date: 08/Sep/21 04:39
    Worklog Time Spent: 10m 
      Work Description: ferhui merged pull request #3378:
URL: https://github.com/apache/hadoop/pull/3378


   


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Issue Time Tracking
-------------------

    Worklog Id:     (was: 647723)
    Time Spent: 3h  (was: 2h 50m)

> Add description for dfs.namenode.caching.enabled
> ------------------------------------------------
>
>                 Key: HDFS-16209
>                 URL: https://issues.apache.org/jira/browse/HDFS-16209
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>    Affects Versions: 3.1.0
>            Reporter: tomscut
>            Assignee: tomscut
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 3h
>  Remaining Estimate: 0h
>
> Namenode config:
>  dfs.namenode.write-lock-reporting-threshold-ms=50ms
>  dfs.namenode.caching.enabled=true (default)
>  
> In fact, the caching feature is not used in our cluster, but this switch is 
> turned on by default(dfs.namenode.caching.enabled=true), incurring some 
> additional write lock overhead. We count the number of write lock warnings in 
> a log file, and find that the number of rescan cache warnings reaches about 
> 32%, which greatly affects the performance of Namenode.
> !namenode-write-lock.jpg!
>  
> We should set 'dfs.namenode.caching.enabled' to false by default and turn it 
> on when we wants to use it.



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