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https://issues.apache.org/jira/browse/HDFS-6788?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14083017#comment-14083017
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Andrew Wang commented on HDFS-6788:
-----------------------------------
As an FYI, I just did a quick revert + fix for the branch-2 version of this
since the SVN merge messed up (a brace was in the wrong place, but no conflict).
> 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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