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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1093) Improve namenode scalability by splitting the FSNamesystem synchronized section in a read/write lock
Date Thu, 16 Sep 2010 16:36:39 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1093?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12910216#action_12910216
] 

dhruba borthakur commented on HDFS-1093:
----------------------------------------


     [exec]     +1 @author.  The patch does not contain any @author tags.
     [exec] 
     [exec]     -1 tests included.  The patch doesn't appear to include any new or modified
tests.
     [exec]                         Please justify why no new tests are needed for this patch.
     [exec]                         Also please list what manual steps were performed to verify
this patch.
     [exec] 
     [exec]     +1 javadoc.  The javadoc tool did not generate any warning messages.
     [exec] 
     [exec]     +1 javac.  The applied patch does not increase the total number of javac compiler
warnings.
     [exec] 
     [exec]     +1 findbugs.  The patch does not introduce any new Findbugs warnings.
     [exec] 
     [exec]     +1 release audit.  The applied patch does not increase the total number of
release audit warnings.
     [exec] 
     [exec]     +1 system tests framework.  The patch passed system tests framework compile.


> Improve namenode scalability by splitting the FSNamesystem synchronized section in a
read/write lock
> ----------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-1093
>                 URL: https://issues.apache.org/jira/browse/HDFS-1093
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>             Fix For: 0.22.0
>
>         Attachments: NNreadwriteLock.txt, NNreadwriteLock_trunk_1.txt, NNreadwriteLock_trunk_2.txt,
NNreadwriteLock_trunk_3.txt, NNreadwriteLock_trunk_4.txt, NNreadwriteLock_trunk_5.txt
>
>
> Most critical data structures in the NameNode (NN) are protected by a syncronized methods
in the FSNamesystem class. This essentially makes critical code paths in the NN single-threaded.
However, a large percentage of the NN calls are listStatus, getBlockLocations, etc which do
not change internal data structures at all, these are read-only calls. If we change the FSNamesystem
lock to a read/write lock, many of the above operations can occur in parallel, thus improving
the scalability of the NN.

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