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From "Jay Booth (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HDFS-918) Use single Selector and small thread pool to replace many instances of BlockSender for reads
Date Wed, 24 Mar 2010 19:59:27 GMT

     [ https://issues.apache.org/jira/browse/HDFS-918?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jay Booth updated HDFS-918:
---------------------------

    Attachment: hdfs-200+826+918-branch20.patch

I heard all the cool kids are running HDFS-200 and HDFS-826 on their 0.20.2 installations
these days, so I merged HDFS-918 with them.

Also, nobody use the existing 0.20.2 patch, I'll delete now and post a new one tonight --
it happens to be missing a very important Thread.start() invocation.

> Use single Selector and small thread pool to replace many instances of BlockSender for
reads
> --------------------------------------------------------------------------------------------
>
>                 Key: HDFS-918
>                 URL: https://issues.apache.org/jira/browse/HDFS-918
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: data-node
>            Reporter: Jay Booth
>             Fix For: 0.22.0
>
>         Attachments: hdfs-200+826+918-branch20.patch, hdfs-918-20100201.patch, hdfs-918-20100203.patch,
hdfs-918-20100211.patch, hdfs-918-20100228.patch, hdfs-918-20100309.patch, hdfs-multiplex.patch
>
>
> Currently, on read requests, the DataXCeiver server allocates a new thread per request,
which must allocate its own buffers and leads to higher-than-optimal CPU and memory usage
by the sending threads.  If we had a single selector and a small threadpool to multiplex request
packets, we could theoretically achieve higher performance while taking up fewer resources
and leaving more CPU on datanodes available for mapred, hbase or whatever.  This can be done
without changing any wire protocols.

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