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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 05:46:09 GMT

    [ https://issues.apache.org/jira/browse/HBASE-6755?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13453732#comment-13453732
] 

Lars Hofhansl commented on HBASE-6755:
--------------------------------------

Just did a quick test (on my poor 2 core laptop): Ran PE with RandomWrite with 50 Threads
(nomapred, ROWS=5000). I added logging to the case where we have to reset the "idGenerator"
from the random number. With this patch I find that it happened 10 times, without the patch
it did not happen at all. With more cores this effect will be more pronounced - I'll try tomorrow
on my work desktop with 12 HW threads (6 cores, 2 hyper threads per core).
                
> 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
one.
> In a very unscientific test I saw the %system CPU reduced when the AtomicInteger is avoided.

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