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Yi Liu commented on HDFS-8912: ------------------------------ Hi [~cmccabe], how do you think about it? Thanks. > Implement ShrinkableHashMap extends java HashMap and use properly > ----------------------------------------------------------------- > > Key: HDFS-8912 > URL: https://issues.apache.org/jira/browse/HDFS-8912 > Project: Hadoop HDFS > Issue Type: Sub-task > Reporter: Yi Liu > Assignee: Yi Liu > > Currently {{LightWeightHashSet}} and {{LightWeightLinkedSet}} are used in > hdfs, there are two advantages compared to java HashSet: one is the entry > requires fewer memory, another is it's shrinkable. In real cluster, hdfs is > a long running service, and {{set}} may become very large at some time and > may become small after that, so shrinking the {{set}} when size hits the > shrink threshold is necessary, it can improve the NN memory. > Same situation for {{map}}, some HashMap used in BlockManager (e.g., the > hashmap in CorruptReplicasMap), it's better to be shrinkable. > I think it's worth to implement ShrinkableHashMap extends the java HashMap, > for quick glance, seems few code is needed. -- This message was sent by Atlassian JIRA (v6.3.4#6332)