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From "Arpit Agarwal (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6788) Improve synchronization in BPOfferService with read write lock
Date Fri, 01 Aug 2014 00:41:38 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6788?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14081748#comment-14081748
] 

Arpit Agarwal commented on HDFS-6788:
-------------------------------------

Thanks Andrew/Yongjun for verifying the lock order correctness.

Just reviewed and +1 from me also, pending Jenkins.

> 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
>         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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