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Date: Fri, 1 Aug 2014 21:53:39 +0000 (UTC)
From: "Andrew Wang (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12730805.1406733072898.98910.1406930019578@arcas>
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Subject: [jira] [Commented] (HDFS-6788) Improve synchronization in
 BPOfferService with read write lock
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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 ] 

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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