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Date: Wed, 23 Jan 2008 17:06:35 -0800 (PST)
From: "Nigel Daley (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Updated: (HADOOP-2232) Add option to disable nagles
 algorithm in the IPC Server
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     [ https://issues.apache.org/jira/browse/HADOOP-2232?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Nigel Daley updated HADOOP-2232:
--------------------------------

    Fix Version/s: 0.16.0

This should have been assigned to 0.16.  It was PA before the feature freeze.

> 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
>             Fix For: 0.16.0
>
>         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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