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Date: Mon, 22 May 2017 08:49:04 +0000 (UTC)
From: "Yu Li (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] [Commented] (HBASE-18085) Prevent parallel purge in
 ObjectPool
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archived-at: Mon, 22 May 2017 08:49:09 -0000


    [ https://issues.apache.org/jira/browse/HBASE-18085?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16019300#comment-16019300 ] 

Yu Li commented on HBASE-18085:
-------------------------------

From the micro benchmark result, tryLock is much better. Let me know if any question on the benchmark code/result, thanks. [~anoop.hbase]

> 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
>
>
> 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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