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From "stack (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 Mon, 03 Jan 2011 16:32:50 GMT

    [ https://issues.apache.org/jira/browse/HDFS-918?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12976804#action_12976804
] 

stack commented on HDFS-918:
----------------------------

I ran unit tests and the main difference was failure of  '[junit] Test org.apache.hadoop.hdfs.TestFileConcurrentReader
FAILED' (There seem to be a few failing tests already on this append branch).

@Todd When you say we could get it into 0.23, you thinking all of it or just some pieces of
this patch?

> 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
>            Assignee: Jay Booth
>             Fix For: 0.22.0
>
>         Attachments: hbase-hdfs-benchmarks.ods, hdfs-918-20100201.patch, hdfs-918-20100203.patch,
hdfs-918-20100211.patch, hdfs-918-20100228.patch, hdfs-918-20100309.patch, hdfs-918-branch20-append.patch,
hdfs-918-branch20.2.patch, hdfs-918-pool.patch, hdfs-918-TRUNK.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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