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From "Yongjun Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6788) Improve synchronization in BPOfferService with read write lock
Date Thu, 31 Jul 2014 18:43:39 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6788?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14081258#comment-14081258
] 

Yongjun Zhang commented on HDFS-6788:
-------------------------------------

HI Arpit, this is trying to address an important issue. I know that you might be too busy
right now. I will get some help from other folks for reviewing in case you won't be able to
get to it soon. thanks.



> 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
>
>
> 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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