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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-4049) hflush performance regression due to nagling delays
Date Mon, 15 Oct 2012 18:46:04 GMT

     [ https://issues.apache.org/jira/browse/HDFS-4049?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Todd Lipcon updated HDFS-4049:
------------------------------

    Attachment: hdfs-4049.txt

Thanks for the reviews. Addressed both the suggestions above. I also added a new unit test
specifically for PacketReceiver in isolation, since some of the buffer handling is tricky.
                
> hflush performance regression due to nagling delays
> ---------------------------------------------------
>
>                 Key: HDFS-4049
>                 URL: https://issues.apache.org/jira/browse/HDFS-4049
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: data-node, performance
>    Affects Versions: 3.0.0, 2.0.2-alpha
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Critical
>         Attachments: hdfs-4049.txt, hdfs-4049.txt
>
>
> HDFS-3721 reworked the way that packets are mirrored through the pipeline in the datanode.
This caused two write() calls where there used to be one, which interacts badly with nagling
so that there are 40ms bubbles on hflush() calls. We didn't notice this in the tests because
the hflush perf test only uses a single datanode.

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