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https://issues.apache.org/jira/browse/HBASE-3894?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13037086#comment-13037086
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Jean-Daniel Cryans commented on HBASE-3894:
-------------------------------------------
I gave the latest patch a spin on my laptop using two PE randomWrite 1 (to
generate lock contention) and my CPU profiling doesn't see any slowness related
to the locking and the memory profiling shows that ~10k CountDownLatch only
accounts for ~300KB. Also since they are short lived they get cleared up almost
right away.
I would be +1 on committing if Dave tried it out on his cluster.
> 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
> Priority: Blocker
> Fix For: 0.90.4
>
> Attachments: concurrentRowLocks-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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