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https://issues.apache.org/jira/browse/HBASE-18085?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Yu Li updated HBASE-18085:
--------------------------
    Attachment: HBASE-18085.patch

Minor change to trigger UT on hbase-server

> Prevent parallel purge in ObjectPool
> ------------------------------------
>
>                 Key: HBASE-18085
>                 URL: https://issues.apache.org/jira/browse/HBASE-18085
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Yu Li
>            Assignee: Yu Li
>         Attachments: e89l05465.st3.jstack, HBASE-18085.patch, 
> HBASE-18085.patch
>
>
> Parallel purge in ObjectPool is meaningless and will cause contention issue 
> since {{ReferenceQueue#poll}} has synchronization (source code shown below)
> {code}
>     public Reference<? extends T> poll() {
>         if (head == null)
>             return null;
>         synchronized (lock) {
>             return reallyPoll();
>         }
>     }
> {code}
> We observed threads blocking on the purge method while using offheap bucket 
> cache, and we could easily reproduce this by testing the 100% cache hit case 
> in bucket cache with enough reading threads.
> We propose to add a purgeLock and use tryLock to avoid parallel purge.



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