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https://issues.apache.org/jira/browse/HDFS-4184?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Todd Lipcon resolved HDFS-4184.
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Resolution: Duplicate
> Add the ability for Client to provide more hint information for DataNode to
> manage the OS buffer cache more accurate
> --------------------------------------------------------------------------------------------------------------------
>
> Key: HDFS-4184
> URL: https://issues.apache.org/jira/browse/HDFS-4184
> Project: Hadoop HDFS
> Issue Type: New Feature
> Reporter: binlijin
>
> HDFS now has the ability to use posix_fadvise and sync_data_range syscalls to
> manage the OS buffer cache.
> {code}
> When hbase read hlog the data we can set dfs.datanode.drop.cache.behind.reads
> to true to drop data out of the buffer cache when performing sequential reads.
> When hbase write hlog we can set dfs.datanode.drop.cache.behind.writes to
> true to drop data out of the buffer cache after writing
> When hbase read hfile during compaction we can set
> dfs.datanode.readahead.bytes to a non-zero value to trigger readahead for
> sequential reads， and also set dfs.datanode.drop.cache.behind.reads to true
> to drop data out of the buffer cache when performing sequential reads.
> and so on...
> {code}
> Current we can only set these feature global in datanode，we should set these
> feature per session.
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