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https://issues.apache.org/jira/browse/HADOOP-2232?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12561816#action_12561816 ]
Mukund Madhugiri commented on HADOOP-2232:
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Ok. Here is the data from the latest trunk. I did a run last night on trunk and *see* the exceptions on trunk as well. Here are the new trunk numbers and comparing them with the trunk + patch numbers, this patch looks good.
|*500 nodes*|*trunk*|*trunk + patch*|*Difference (%)*|
|randomWriter (mins)|29|28| ( -1.8% )
|sort (mins)|110|113| ( 2% )
> Add option to disable nagles algorithm in the IPC Server
> --------------------------------------------------------
>
> Key: HADOOP-2232
> URL:
https://issues.apache.org/jira/browse/HADOOP-2232> Project: Hadoop Core
> Issue Type: Improvement
> Components: ipc
> Affects Versions: 0.16.0
> Reporter: Clint Morgan
> Assignee: Clint Morgan
> Attachments: 2232-3.patch, HADOOP-2232-1.patch, HADOOP-2232-2.patch
>
>
> While investigating hbase performance, I found a bottleneck caused by
> Nagles algorithm. For some reads I would get a bi-modal distribution
> of read times, with about half the times being around 20ms, and half
> around 200ms. I tracked this down to the well-known interaction between
> Nagle's algorithm and TCP delayed acknowledgments.
> I found that calling setTcpNoDelay(true) on the server's socket
> connection dropped all of my read times back to a constant 20 ms.
> I propose a patch to have this TCP_NODELAY option be configurable. The
> attacked patch allows one to set the TCP_NODELAY option on both the
> client and the server side. Currently this is defaulted to false
> (i.e., with Nagle's enabled).
> To see the effect, I have included a Test which provokes the issue by
> sending a MapWriteable over an IPC call. On my machine this test shows
> a speedup of 117 times when using TCP_NODELAY.
> These tests were done on OSX 10.4. Your milage may very with other
> TCP/IP implementation stacks.
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