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https://issues.apache.org/jira/browse/HBASE-22422?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16840130#comment-16840130
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Zheng Hu commented on HBASE-22422:
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An potential cause would be here:
https://issues.apache.org/jira/secure/attachment/12968762/LRUBlockCache-getBlock.png
1. get block from map firstly;
2. retain the bock.
Between the step.1 and step.2, if a release to zero happen, then we'll get
the Exception which says we are retaining a block with refCnt=0.
> Retain an ByteBuff with refCnt=0 when getBlock from LRUCache
> ------------------------------------------------------------
>
> Key: HBASE-22422
> URL: https://issues.apache.org/jira/browse/HBASE-22422
> Project: HBase
> Issue Type: Sub-task
> Reporter: Zheng Hu
> Assignee: Zheng Hu
> Priority: Major
> Attachments: LRUBlockCache-getBlock.png,
> image-2019-05-15-12-00-03-641.png
>
>
> After runing YCSB scan/get benchmark in our XiaoMi cluster, we found the get
> QPS dropped from 25000/s to hunderds per second in a cluster with five
> nodes.
> After enable the debug log at YCSB client side, I found the following
> stacktrace , see
> https://issues.apache.org/jira/secure/attachment/12968745/image-2019-05-15-12-00-03-641.png
> Need a patch to fix this.
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