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https://issues.apache.org/jira/browse/HDFS-6788?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14083591#comment-14083591
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Hudson commented on HDFS-6788:
------------------------------

SUCCESS: Integrated in Hadoop-Mapreduce-trunk #1850 (See 
[https://builds.apache.org/job/Hadoop-Mapreduce-trunk/1850/])
HDFS-6788. Improve synchronization in BPOfferService with read write lock. 
Contributed by Yongjun Zhang. (wang: 
http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1615190)
* /hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
* 
/hadoop/common/trunk/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPOfferService.java


> Improve synchronization in BPOfferService with read write lock
> --------------------------------------------------------------
>
>                 Key: HDFS-6788
>                 URL: https://issues.apache.org/jira/browse/HDFS-6788
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>    Affects Versions: 2.5.0
>            Reporter: Yongjun Zhang
>            Assignee: Yongjun Zhang
>             Fix For: 2.6.0
>
>         Attachments: HDFS-6788.001.patch, HDFS-6788.002.patch
>
>
> Threads in DN (DataXceiver, PacketResponder, Async disk worker etc) may block 
> at BPOfferService.getBlockPoolId() when calling BPOfferService.checkBlock(), 
> though they are just reading the same blockpool id. This is unnecessary 
> overhead and may cause performance hit when many threads compete. Filing this 
> jira to replace synchronized method with read write lock 
> (ReentrantReadWriteLock).



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