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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1093) Improve namenode scalability by splitting the FSNamesystem synchronized section in a read/write lock
Date Wed, 15 Sep 2010 04:51:38 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1093?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12909590#action_12909590

Hadoop QA commented on HDFS-1093:

-1 overall.  Here are the results of testing the latest attachment 
  against trunk revision 997157.

    +1 @author.  The patch does not contain any @author tags.

    -1 tests included.  The patch doesn't appear to include any new or modified tests.
                        Please justify why no new tests are needed for this patch.
                        Also please list what manual steps were performed to verify this patch.

    -1 patch.  The patch command could not apply the patch.

Console output: http://hudson.zones.apache.org/hudson/job/Hdfs-Patch-h2.grid.sp2.yahoo.net/240/console

This message is automatically generated.

> 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
> 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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