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From "Andrew Wang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9201) Namenode Performance Improvement : Using for loop without iterator
Date Fri, 09 Oct 2015 20:47:05 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9201?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14951162#comment-14951162
] 

Andrew Wang commented on HDFS-9201:
-----------------------------------

So in the mentioned HBASE jira, it looks like they added asserts to make sure the lists supported
random access. Nijel, could we do this here too? This would address Staffan's comment.

I think the performance benchmarks also speak for themselves, even without GC stats (though
those would be nice too).

> Namenode Performance Improvement : Using for loop without iterator
> ------------------------------------------------------------------
>
>                 Key: HDFS-9201
>                 URL: https://issues.apache.org/jira/browse/HDFS-9201
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: nijel
>            Assignee: nijel
>              Labels: namenode, performance
>         Attachments: HDFS-9201_draft.patch
>
>
> As discussed in HBASE-12023, the for each loop syntax will create few extra objects and
garbage.
> For arrays and Lists can change to the traditional syntax. 
> This can improve memory foot print and can result in performance gain.



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