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https://issues.apache.org/jira/browse/HDFS-918?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12844191#action_12844191
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Jay Booth commented on HDFS-918:
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I'll enthusiastically cheerlead? :)
More seriously, I'm willing to put in the work to get everyone to a comfort
level with this patch so it gets committed in some form and we get some wins
out of it, but the write path is more complicated, I don't understand it as
well and I'm honestly going to need a little bit of a break over the summer.
I'd love to help in whatever way I can but I'm probably not going to have the
bandwidth to be the main driver of it in the short term.. I don't fully grok
the write pipeline and the intricacies of append yet, so at the least someone
else would have to be involved.
> 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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