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https://issues.apache.org/jira/browse/HDFS-16209?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Shilun Fan updated HDFS-16209:
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Component/s: documentation
Hadoop Flags: Reviewed
Target Version/s: 3.4.0
> 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
> Components: documentation
> Affects Versions: 3.1.0
> Reporter: Tao Li
> Assignee: Tao Li
> Priority: Major
> Labels: pull-request-available
> Fix For: 3.4.0
>
> Time Spent: 3h 20m
> 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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