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https://issues.apache.org/jira/browse/HDFS-5453?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13855489#comment-13855489
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Edward Bortnikov commented on HDFS-5453:
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Orthogonally to the recent thread ... Attached is a spreadsheet with simulation
results that exemplify the ballpark gain from transitioning to a completely
lock-free architecture. It is based on a very recent Hadoop 2.0 code.
This is more of a long-term feature, which we believe is what the namenode
ultimately needs.
> Support fine grain locking in FSNamesystem
> ------------------------------------------
>
> Key: HDFS-5453
> URL: https://issues.apache.org/jira/browse/HDFS-5453
> Project: Hadoop HDFS
> Issue Type: New Feature
> Components: namenode
> Affects Versions: 2.0.0-alpha, 3.0.0
> Reporter: Daryn Sharp
> Assignee: Daryn Sharp
> Attachments: async_simulation.xlsx
>
>
> The namesystem currently uses a course grain lock to control access. This
> prevents concurrent writers in different branches of the tree, and prevents
> readers from accessing branches that writers aren't using.
> Features that introduce latency to namesystem operations, such as cold
> storage of inodes, will need fine grain locking to avoid degrading the entire
> namesystem's throughput.
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