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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 Tue, 30 Mar 2010 22:30:29 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-918-branch20.2.patch

Cleaned up a bug in the BlockChannelPool.cleanup() code, added new unit test, improved descriptions
of new config values (useMultiplex, packetSize, maxOpenBlockChannels, minOpenBlockchannels
(number to cleanup() to)).

This patch is for branch 20, I'll post a new one against trunk tonight.

> 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-918-20100201.patch, hdfs-918-20100203.patch, hdfs-918-20100211.patch,
hdfs-918-20100228.patch, hdfs-918-20100309.patch, hdfs-918-branch20.2.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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