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From "Misha Dmitriev (JIRA)" <j...@apache.org>
Subject [jira] [Created] (YARN-7302) Configuration.updatingResource map should be initialized lazily
Date Mon, 09 Oct 2017 19:37:00 GMT
Misha Dmitriev created YARN-7302:

             Summary: Configuration.updatingResource map should be initialized lazily
                 Key: YARN-7302
                 URL: https://issues.apache.org/jira/browse/YARN-7302
             Project: Hadoop YARN
          Issue Type: Improvement
            Reporter: Misha Dmitriev

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:

905,551K (24.0%): java.util.concurrent.ConcurrentHashMap: 22118 / 100% of empty 905,551K (24.0%)
↖Java Static org.apache.hadoop.conf.Configuration.REGISTRY

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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