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From "Chris Nauroth (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7456) De-duplicate AclFeature instances with same AclEntries do reduce memory footprint of NameNode
Date Sat, 20 Dec 2014 00:47:13 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7456?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14254371#comment-14254371
] 

Chris Nauroth commented on HDFS-7456:
-------------------------------------

Thanks again, Vinay.  This is looking good, and the tests are very thorough.  I have just
a few more nitpicks.

In {{INodeAttributes}}, was it necessary to change the {{SnapshotCopy}} constructor?  The
new version has a slight disadvantage in that calling {{INode#getPermissionStatus}} constructs
a new intermediate {{PermissionStatus}}, which then has to get translated back to {{long}}
representation immediately.  It will generate some additional garbage.

In {{FSAclBaseTest}}, perhaps it's more appropriate to rename {{startSize}} to {{currentSize}},
since it gets incremented in the test when new instances get created.

In the NameNode restart tests, we have the limitation that reference counts are not maintained
between restarts, because the data is {{static}}.  I think it's important to be able to test
this though.  Even though the reference counts won't be decremented during shutdown, we should
know the expected delta of increments done on each feature during the subsequent startup.
 Can we add assertions for that?

> De-duplicate AclFeature instances with same AclEntries do reduce memory footprint of
NameNode
> ---------------------------------------------------------------------------------------------
>
>                 Key: HDFS-7456
>                 URL: https://issues.apache.org/jira/browse/HDFS-7456
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>            Reporter: Vinayakumar B
>            Assignee: Vinayakumar B
>         Attachments: HDFS-7456-001.patch, HDFS-7456-002.patch, HDFS-7456-003.patch, HDFS-7456-004.patch,
HDFS-7456-005.patch, HDFS-7456-006.patch
>
>
> As discussed  in HDFS-7454 [here|https://issues.apache.org/jira/browse/HDFS-7454?focusedCommentId=14229454&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14229454],
de-duplication of {{AclFeature}} helps in reducing the memory footprint of the namenode.



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