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https://issues.apache.org/jira/browse/HDFS-3898?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13450878#comment-13450878
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Colin Patrick McCabe commented on HDFS-3898:
--------------------------------------------
Looks good to me.
Just one small nit. Nagle can trigger even when writing less than the MTU,
though, right? I thought its primary use was coalescing lots of small packets
into fewer big ones. The comment seems to imply that this is only a problem if
you're writing more than the MTU in a batch, but it seems like Nagle could be a
problem even if you don't do this.
> 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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