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https://issues.apache.org/jira/browse/HBASE-18085?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16020668#comment-16020668
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Anoop Sam John commented on HBASE-18085:
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In ur test method for tryLock, there is no logic other than just try lock and
release. If that is been removed as dead code by compiler? One way to avoid
that is using the return value. See BlackHole in JMH and its usage.. The diff
in numbers that reported by JMH benchmark is so huge! The impl of tryLock is
having a volatile read and all. So this huge diff in numbers looks strange
no? That was my doubt.
> 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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