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Posted to hdfs-dev@hadoop.apache.org by "Todd Lipcon (JIRA)" <ji...@apache.org> on 2013/01/18 00:12:16 UTC

[jira] [Resolved] (HDFS-4418) HDFS-347: increase default FileInputStreamCache size

     [ https://issues.apache.org/jira/browse/HDFS-4418?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Todd Lipcon resolved HDFS-4418.
-------------------------------

      Resolution: Fixed
    Hadoop Flags: Reviewed

Committed to branch.
                
> HDFS-347: increase default FileInputStreamCache size
> ----------------------------------------------------
>
>                 Key: HDFS-4418
>                 URL: https://issues.apache.org/jira/browse/HDFS-4418
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: datanode, hdfs-client, performance
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>         Attachments: hdfs-4418.txt
>
>
> The FileInputStreamCache currently defaults to holding only 10 input stream pairs (corresponding to 10 blocks). In many HBase workloads, the region server will be issuing random reads against a local file which is 2-4GB in size or even larger (hence 20+ blocks).
> Given that the memory usage for caching these input streams is low, and applications like HBase tend to already increase their ulimit -n substantially (eg up to 32,000), I think we should raise the default cache size to 50 or more. In the rare case that someone has an application which uses local reads with hundreds of open blocks and can't feasibly raise their ulimit -n, they can lower the limit appropriately.

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