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https://issues.apache.org/jira/browse/HDFS-16043?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17470349#comment-17470349
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Yongpan Liu commented on HDFS-16043:
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We have used Xiangyi Zhu's patch for online production and it works well.
In our scenario, the quota calculation is skipped so that the impact of the
delete on NN is less.
> Add markedDeleteBlockScrubberThread to delete blocks asynchronously
> -------------------------------------------------------------------
>
> Key: HDFS-16043
> URL: https://issues.apache.org/jira/browse/HDFS-16043
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs, namanode
> Affects Versions: 3.4.0
> Reporter: Xiangyi Zhu
> Assignee: Xiangyi Zhu
> Priority: Major
> Labels: pull-request-available
> Attachments: 20210527-after.svg, 20210527-before.svg
>
> Time Spent: 5h 20m
> Remaining Estimate: 0h
>
> The deletion of the large directory caused NN to hold the lock for too long,
> which caused our NameNode to be killed by ZKFC.
> Through the flame graph, it is found that its main time-consuming
> calculation is QuotaCount when removingBlocks(toRemovedBlocks) and deleting
> inodes, and removeBlocks(toRemovedBlocks) takes a higher proportion of time.
> h3. solution:
> 1. RemoveBlocks is processed asynchronously. A thread is started in the
> BlockManager to process the deleted blocks and control the lock time.
> 2. QuotaCount calculation optimization, this is similar to the optimization
> of this Issue HDFS-16000.
> h3. Comparison before and after optimization:
> Delete 1000w Inode and 1000w block test.
> *before:*
> remove inode elapsed time: 7691 ms
> remove block elapsed time :11107 ms
> *after:*
> remove inode elapsed time: 4149 ms
> remove block elapsed time :0 ms
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