hadoop-hdfs-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Edward Bortnikov (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5453) Support fine grain locking in FSNamesystem
Date Wed, 18 Dec 2013 13:32:13 GMT

    [ 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

View raw message