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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1110) Namenode heap optimization - reuse objects for commonly used file names
Date Mon, 10 May 2010 19:36:31 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1110?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12865889#action_12865889
] 

dhruba borthakur commented on HDFS-1110:
----------------------------------------

Thanks Suresh for the numbers.

> agree with Dhruba that we need to optimize only for the top ten (or so) file names, which
will give us 5% saving in the meta

One fear I have is that the regex matching inside the fsnamesystem lock could increase CPU
increase in such a way that the 5% gain in memory might not be a good tradeoff. any thoughts
on this?

> Namenode heap optimization - reuse objects for commonly used file names
> -----------------------------------------------------------------------
>
>                 Key: HDFS-1110
>                 URL: https://issues.apache.org/jira/browse/HDFS-1110
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Suresh Srinivas
>            Assignee: Suresh Srinivas
>             Fix For: 0.22.0
>
>         Attachments: hdfs-1110.2.patch, hdfs-1110.patch
>
>
> There are a lot of common file names used in HDFS, mainly created by mapreduce, such
as file names starting with "part". Reusing byte[] corresponding to these recurring file names
will save significant heap space used for storing the file names in millions of INodeFile
objects.

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