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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-6755) HRegion.internalObtainRowLock uses unecessary AtomicInteger
Date Wed, 12 Sep 2012 06:03:08 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6755?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13453749#comment-13453749

Lars Hofhansl commented on HBASE-6755:

Interestingly, if I just try to increment the idGenerator twice the other core never sees
a stale value. This is probably due to ConcurrentHashMap taking out a memory barrier anyway...
Which incidentally makes this whole issue a moot point.
I'll play a bit more tomorrow and probably close as "Invalid".
> HRegion.internalObtainRowLock uses unecessary AtomicInteger
> -----------------------------------------------------------
>                 Key: HBASE-6755
>                 URL: https://issues.apache.org/jira/browse/HBASE-6755
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>             Fix For: 0.96.0, 0.94.3
>         Attachments: 6755-0.96.txt
> I was looking at HBase's implementation of locks and saw that is unnecessarily uses an
AtomicInteger to obtain a unique lockid.
> The observation is that we only need a unique one and don't care if we happen to skip
> In a very unscientific test I saw the %system CPU reduced when the AtomicInteger is avoided.

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