liaoyuxiangqin created HDFS-13883:
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Summary: Reduce memory consumption and GC of directory scan
Key: HDFS-13883
URL: https://issues.apache.org/jira/browse/HDFS-13883
Project: Hadoop HDFS
Issue Type: Improvement
Affects Versions: 3.2.0
Reporter: liaoyuxiangqin
When DirectoryScan task have trigger in periodic, the scan thread to scan
all disk in this
DataNode for all blockpool, and construct a ScanInfo per block. So DataNode
need huge memory to hold those ScanInfo's memory structure when tens of
millions blocks store in this DataNode.
Another problem is DataNode implements by java, so DataNode run as a JVM，
so we need to set a big number for -Xmx to satisfy the memory needs of
DirectoryScan. But we know the default period of DirectoryScan is 6 hours, and
at other time DataNode actually need less memory, and JVM can't auto return
free memory to OS, so many memory utilization rate is low.
At last, we have test close or open DirectoryScan in thirty-millions
blocks store in the DataNode, and the -Xmx set is 16G and 32G respectively.So
i think we can improve the
DirectoryScan process and save memory such as scan one block pool per period,
thanks.
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