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https://issues.apache.org/jira/browse/HDFS-918?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12844620#action_12844620
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Raghu Angadi commented on HDFS-918:
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> RE: Netty, I'm not very knowledgeable about it beyond the Cliff's Notes
> version, but my code dealing with the Selector is pretty small - the main
> loop is under 75 lines, and java.util.concurrent does most of the heavy
> lifting
Jay, I think is ok to ignore Netty for this jira. it could be re-factored later.
>> I think it is very important to have separate pools for each partition.
> This would be the case if I were using a fixed-size thread pool and a
> LinkedBlockingQueue - but I'm not, see Executors.newCachedThreadPool(),
hmm.. does it mean that if you have thousand clients and the load is disk
bound, we end up with 1000 threads?
> 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-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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