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https://issues.apache.org/jira/browse/HDFS-16433?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Yuanbo Liu resolved HDFS-16433.
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Resolution: Not A Problem
> The synchronized lock of IncrementalBlockReportManager will slow down the
> speed of creating/deleting/finalizing/opening block
> -----------------------------------------------------------------------------------------------------------------------------
>
> Key: HDFS-16433
> URL: https://issues.apache.org/jira/browse/HDFS-16433
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Yuanbo Liu
> Priority: Critical
> Attachments: image-2022-01-21-22-52-52-912.png
>
>
> The code in IncrementalBlockReportManager.java
> {code:java}
> synchronized void waitTillNextIBR(long waitTime) {
> if (waitTime > 0 && !sendImmediately()) {
> try {
> wait(ibrInterval > 0 && ibrInterval < waitTime? ibrInterval: waitTime);
> } catch (InterruptedException ie) {
> LOG.warn(getClass().getSimpleName() + " interrupted");
> }
> }
> } {code}
> We can see that wait(waitime) will hold synchronized, if ibr interval is
> enabled or heartbeat time is not reached. The lock will block
> notifyNamenodeBlock function which is widely used in
> deleting/creating/finalizing/opening blocks, then the speed of DataNode IO
> will slow down. Here is the graph of blocking relationship
> !image-2022-01-21-22-52-52-912.png|width=976,height=299!
>
>
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