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https://issues.apache.org/jira/browse/HADOOP-9956?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13822405#comment-13822405
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Hudson commented on HADOOP-9956:
--------------------------------
FAILURE: Integrated in Hadoop-Mapreduce-trunk #1608 (See
[https://builds.apache.org/job/Hadoop-Mapreduce-trunk/1608/])
Move HADOOP-9956 to correct release in CHANGES.txt (daryn:
http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1541740)
* /hadoop/common/trunk/hadoop-common-project/hadoop-common/CHANGES.txt
HADOOP-9956. RPC listener inefficiently assigns connections to readers (daryn)
(daryn: http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1541736)
* /hadoop/common/trunk/hadoop-common-project/hadoop-common/CHANGES.txt
*
/hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/CommonConfigurationKeys.java
*
/hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Server.java
*
/hadoop/common/trunk/hadoop-common-project/hadoop-common/src/test/java/org/apache/hadoop/ipc/TestIPC.java
> 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
> Fix For: 3.0.0, 2.3.0, 0.23.10
>
> Attachments: HADOOP-9956.branch-23.patch, 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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