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Date: Mon, 11 Nov 2013 20:09:19 +0000 (UTC)
From: "Hadoop QA (JIRA)" <jira@apache.org>
To: common-issues@hadoop.apache.org
Message-ID: <JIRA.12668177.1378942549223.53154.1384200559331@arcas>
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References: <JIRA.12668177.1378942549223@arcas>
Subject: [jira] [Commented] (HADOOP-9956) RPC listener inefficiently assigns
 connections to readers
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    [ https://issues.apache.org/jira/browse/HADOOP-9956?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13819313#comment-13819313 ] 

Hadoop QA commented on HADOOP-9956:
-----------------------------------

{color:green}+1 overall{color}.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12613204/HADOOP-9956.patch
  against trunk revision .

    {color:green}+1 @author{color}.  The patch does not contain any @author tags.

    {color:green}+1 tests included{color}.  The patch appears to include 1 new or modified test files.

    {color:green}+1 javac{color}.  The applied patch does not increase the total number of javac compiler warnings.

    {color:green}+1 javadoc{color}.  The javadoc tool did not generate any warning messages.

    {color:green}+1 eclipse:eclipse{color}.  The patch built with eclipse:eclipse.

    {color:green}+1 findbugs{color}.  The patch does not introduce any new Findbugs (version 1.3.9) warnings.

    {color:green}+1 release audit{color}.  The applied patch does not increase the total number of release audit warnings.

    {color:green}+1 core tests{color}.  The patch passed unit tests in hadoop-common-project/hadoop-common.

    {color:green}+1 contrib tests{color}.  The patch passed contrib unit tests.

Test results: https://builds.apache.org/job/PreCommit-HADOOP-Build/3272//testReport/
Console output: https://builds.apache.org/job/PreCommit-HADOOP-Build/3272//console

This message is automatically generated.

> RPC listener inefficiently assigns connections to readers
> ---------------------------------------------------------
>
>                 Key: HADOOP-9956
>                 URL: https://issues.apache.org/jira/browse/HADOOP-9956
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: ipc
>    Affects Versions: 2.0.0-alpha, 3.0.0
>            Reporter: Daryn Sharp
>            Assignee: Daryn Sharp
>         Attachments: HADOOP-9956.patch, HADOOP-9956.patch
>
>
> The socket listener and readers use a complex synchronization to update the reader's NIO {{Selector}}.  Updating active selectors is not thread-safe so precautions are required.
> However, the current locking choreography results in a serialized distribution of new connections to the parallel socket readers.  A slower/busier reader can stall the listener and throttle performance.
> The problem manifests as unexpectedly low cpu utilization by the listener and readers (~20-30%) under heavy load.  The call queue is shallow when it should be overflowing.


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