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https://issues.apache.org/jira/browse/HADOOP-14938?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16204173#comment-16204173
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Robert Kanter commented on HADOOP-14938:
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[[email protected]], the patch only applies to trunk and doesn't cleanly
apply to branch-3.0 or branch-2. Can you upload a version (or versions) of the
patch that does? I'd like to include this in those releases.
> Configuration.updatingResource map should be initialized lazily
> ---------------------------------------------------------------
>
> Key: HADOOP-14938
> URL: https://issues.apache.org/jira/browse/HADOOP-14938
> Project: Hadoop Common
> Issue Type: Improvement
> Reporter: Misha Dmitriev
> Assignee: Misha Dmitriev
> Attachments: HADOOP-14938.01.patch, HADOOP-14938.02.patch,
> HADOOP-14938.03.patch
>
>
> Using jxray (www.jxray.com), I've analyzed a heap dump of YARN RM running in
> a big cluster. The tool uncovered several inefficiencies in the RM memory. It
> turns out that one of the biggest sources of memory waste, responsible for
> almost 1/4 of used memory, is empty ConcurrentHashMap instances in
> org.apache.hadoop.conf.Configuration.updatingResource:
> {code}
> 905,551K (24.0%): java.util.concurrent.ConcurrentHashMap: 22118 / 100% of
> empty 905,551K (24.0%)
> ↖org.apache.hadoop.conf.Configuration.updatingResource
> ↖{j.u.WeakHashMap}.keys
> ↖Java Static org.apache.hadoop.conf.Configuration.REGISTRY
> {code}
> That is, there are 22118 empty ConcurrentHashMaps here, and they collectively
> waste ~905MB of memory. This is caused by eager initialization of these maps.
> To address this problem, we should initialize them lazily.
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