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https://issues.apache.org/jira/browse/HDFS-918?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jay Booth updated HDFS-918:
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Attachment: hdfs-918-20100201.patch
New patch..
* new configuration params: dfs.datanode.multiplexBlockSender=true,
dfs.datanode.multiplex.packetSize=32k, dfs.datanode.multiplex.numWorkers=3
* Packet size is tuneable, possibly allowing better performance with larger TCP
buffers enabled
* Workers only wake up when a connection is writable
* 3 new class files, minor changes to DataXceiverServer and DataXceiver, 2
utility classes added to DataTransferProtocol (one stolen from HDFS-881)
* Passes tests from earlier comment plus a new one for files with lengths that
don't match up to checksum chunk size, as well as holding up to some load on
TestDFSIO
* Still fails all tests relying on SimulatedFSDataset
* Has a large amount of TRACE level debugging going on in
MultiplexedBlockSender in case anybody wants to watch the output
* Adds dependencies for commons-pool and commons-math (for benchmarking code)
* Doesn't yet have benchmarks, but those should be easy now that the
configuration is all in place
> 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-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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