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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-918) Use single Selector and small thread pool to replace many instances of BlockSender for reads
Date Fri, 02 Apr 2010 03:32:27 GMT

    [ https://issues.apache.org/jira/browse/HDFS-918?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12852682#action_12852682

Andrew Purtell commented on HDFS-918:

Sorry, test which contains HBase regionserver abort (due to failure to roll HLog) is here:
http://hbase.s3.amazonaws.com/0.20.3-918-201004020111424808000-sequentialWrite-1.tar.bz2 .
But DN logs are similar for both tests.

> Use single Selector and small thread pool to replace many instances of BlockSender for
> --------------------------------------------------------------------------------------------
>                 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-918-TRUNK.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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