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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3898) QJM: enable TCP_NODELAY for IPC
Date Fri, 07 Sep 2012 03:39:07 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3898?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13450301#comment-13450301

Todd Lipcon commented on HDFS-3898:

This patch has a simple performance test which writes 1000 8kb edits. Prior to the patch,
the average time taken was 40ms per edit due to nagling. After the patch, it's <2ms.
> QJM: enable TCP_NODELAY for IPC
> -------------------------------
>                 Key: HDFS-3898
>                 URL: https://issues.apache.org/jira/browse/HDFS-3898
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>    Affects Versions: QuorumJournalManager (HDFS-3077)
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Blocker
>         Attachments: hdfs-3898.txt
> Currently, if the size of the edits batches is larger than the MTU, it can result in
40ms delays due to interaction between nagle's algorithm and delayed ack. Enabling TCP_NODELAY
on the sockets solves this issue, so we should set those configs by default for all of the
QJM-related IPC.

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