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https://issues.apache.org/jira/browse/HBASE-14268?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Hiroshi Ikeda updated HBASE-14268:
----------------------------------
    Attachment: KeyLockerPerformance.java
                HBASE-14268.patch

Added a patch, and a simple application to check performance.

In my environment the revised KeyLocker is about 10 times faster, aside from 
whether the performance test practically makes sense.

> Improve KeyLocker
> -----------------
>
>                 Key: HBASE-14268
>                 URL: https://issues.apache.org/jira/browse/HBASE-14268
>             Project: HBase
>          Issue Type: Improvement
>          Components: util
>            Reporter: Hiroshi Ikeda
>            Assignee: Hiroshi Ikeda
>            Priority: Minor
>         Attachments: HBASE-14268.patch, KeyLockerPerformance.java
>
>
> 1. In the implementation of {{KeyLocker}} it uses atomic variables inside a 
> synchronized block, which doesn't make sense. Moreover, logic inside the 
> synchronized block is not trivial so that it makes less performance in heavy 
> multi-threaded environment.
> 2. {{KeyLocker}} gives an instance of {{RentrantLock}} which is already 
> locked, but it doesn't follow the contract of {{ReentrantLock}} because you 
> are not allowed to freely invoke lock/unlock methods under that contract. 
> That introduces a potential risk; Whenever you see a variable of the type 
> {{RentrantLock}}, you should pay attention to what the included instance is 
> coming from.



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