[
https://issues.apache.org/jira/browse/HDFS-5453?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13851722#comment-13851722
]
Edward Bortnikov commented on HDFS-5453:
----------------------------------------
Fine grained locking will not expected to have positive performance impact with
a single-process namenode implementation. The execution of every API is so
short that it does not justify acquisition of fine-grained locks along the path
(we have evaluated the performance).
Fine grained locking makes sense (and is a crucial feature) in the context of
block management as a service
(see https://issues.apache.org/jira/browse/HDFS-5477). When block management is
an external process, the NN cannot afford holding a global lock during the RPC.
> 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
>
> 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.
--
This message was sent by Atlassian JIRA
(v6.1.4#6159)
