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https://issues.apache.org/jira/browse/HDFS-1114?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12879633#action_12879633
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Scott Carey commented on HDFS-1114:
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bq. # Capacity should be divided by a reference size 8 or 4 depending on the
64bit or 32bit java version
What about -XX:+UseCompressedOops ?
All users should be using this flag on a 64 bit JVM to save a lot of space. It
only works up to -Xmx32G though, beyond that its large pointers again.
> Reducing NameNode memory usage by an alternate hash table
> ---------------------------------------------------------
>
> Key: HDFS-1114
> URL: https://issues.apache.org/jira/browse/HDFS-1114
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: name-node
> Reporter: Tsz Wo (Nicholas), SZE
> Assignee: Tsz Wo (Nicholas), SZE
> Attachments: GSet20100525.pdf, gset20100608.pdf,
> h1114_20100607.patch, h1114_20100614b.patch, h1114_20100615.patch,
> h1114_20100616b.patch
>
>
> NameNode uses a java.util.HashMap to store BlockInfo objects. When there are
> many blocks in HDFS, this map uses a lot of memory in the NameNode. We may
> optimize the memory usage by a light weight hash table implementation.
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