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https://issues.apache.org/jira/browse/HBASE-18085?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16020775#comment-16020775
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Yu Li commented on HBASE-18085:
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To summarize, volatile boolean is not suitable for this usage since this is not
a "single thread updating, multiple thread reading" case, while AtomicBoolean
and ReentrantLock#tryLock have similar performance according to JMH.
In theory AtomicBoolean is more light-weight, but JMH shows a similar perf, and
in our project tryLock is more frequently used for similar scenario, such as
the {{BucketCache#freeSpaceLock}} and {{MemstoreLABImpl#lock}}, etc. So I still
suggest to follow the old way to use tryLock here, but please feel free to
raise different voice. Thanks.
> 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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