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Date: Wed, 25 May 2011 00:38:47 +0000 (UTC)
From: "Andrew Purtell (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (HBASE-3894) Thread contention over row locks
 set monitor
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    [ https://issues.apache.org/jira/browse/HBASE-3894?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13038896#comment-13038896 ] 

Andrew Purtell commented on HBASE-3894:
---------------------------------------

I have this applied to our 0.90-ish internal branch slated for testing next week as well. It's close enough to 0.90 so the results will be meaningful. Early results in all localhost configuration look reasonable.

> Thread contention over row locks set monitor
> --------------------------------------------
>
>                 Key: HBASE-3894
>                 URL: https://issues.apache.org/jira/browse/HBASE-3894
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.90.2
>            Reporter: Dave Latham
>            Assignee: Dave Latham
>            Priority: Blocker
>             Fix For: 0.90.4
>
>         Attachments: concurrentRowLocks-2.patch, concurrentRowLocks-trunk-2.patch, concurrentRowLocks-trunk.patch, regionserver_rowLock_set_contention.threads.txt
>
>
> HRegion maintains a set of row locks.  Whenever any thread attempts to lock or release a row it needs to acquire the monitor on that set.  We've been encountering cases with 30 handler threads all contending for that monitor, blocked progress on the region server.  Clients timeout, and retry making it worse, and the region server stops responding to new clients almost entirely.

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