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From "Todd Lipcon (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-8069) Enable TCP_NODELAY by default for IPC
Date Tue, 14 Feb 2012 04:13:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-8069?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13207491#comment-13207491
] 

Todd Lipcon commented on HADOOP-8069:
-------------------------------------

A good reason to do this is that, when I run an IPC benchmark on an "echo" function, as soon
as the message size eclipses 8K the latency goes up to 40ms due to the interaction of nagling
and delayed ACK.
                
> Enable TCP_NODELAY by default for IPC
> -------------------------------------
>
>                 Key: HADOOP-8069
>                 URL: https://issues.apache.org/jira/browse/HADOOP-8069
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: ipc
>    Affects Versions: 0.23.0
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>
> I think we should switch the default for the IPC client and server NODELAY options to
true. As wikipedia says:
> {quote}
> In general, since Nagle's algorithm is only a defense against careless applications,
it will not benefit a carefully written application that takes proper care of buffering; the
algorithm has either no effect, or negative effect on the application.
> {quote}
> Since our IPC layer is well contained and does its own buffering, we shouldn't be careless.

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