# Why elasticsearch use so much os memory

**URL:** <https://discuss.elastic.co/t/why-elasticsearch-use-so-much-os-memory/92001>\
**Category:** Elasticsearch\
**Created:** [July 6, 2017, 2:11am UTC](https://discuss.elastic.co/t/why-elasticsearch-use-so-much-os-memory/92001 "2017-07-06T02:11:40Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![xiaodong.hu](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/xiaodong.hu/32/20370_2.png) [@xiaodong.hu](https://discuss.elastic.co/u/xiaodong.hu)\
**Post date:** [July 6, 2017, 2:11am UTC](https://discuss.elastic.co/t/why-elasticsearch-use-so-much-os-memory/92001/1 "2017-07-06T02:11:41Z")

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Hi,

es 5.4.0

I set 16G to elasticsearch JVM, 'ps' prints:  
`/usr/java8/jdk/bin/java -Xms17179869184 -Xmx17179869184 -XX:MaxDirectMemorySize=17179869184 -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/data1/zdh/elasticsearch/logs/elasticsearch_20170705112742_pid12444.hprof -XX:OnOutOfMemoryError=/opt/ZDH/parcels/sbin/common/killparent.sh -XX:+UseConcMarkSweepGC -XX:CMSInitiatingOccupancyFraction=75 -XX:+UseCMSInitiatingOccupancyOnly -XX:+DisableExplicitGC -XX:+AlwaysPreTouch -server -Djava.awt.headless=true -Dfile.encoding=UTF-8 -Djna.nosys=true -Djdk.io.permissionsUseCanonicalPath=true -Dio.netty.noUnsafe=true -Dio.netty.noKeySetOptimization=true -Dio.netty.recycler.maxCapacityPerThread=0 -Dlog4j2.disable.jmx=true -Dlog4j.shutdownHookEnabled=false -Dlog4j.skipJansi=true -Dlog.file=elasticsearch-elasticsearch-elasticsearch-apple101 -Dmax.log.file.size=256MB -Dmax.log.file.backup.index=10 -Dlog.threshold=INFO -Des.path.home=/opt/ZDH/parcels/lib/elasticsearch -cp /opt/ZDH/parcels/lib/elasticsearch/lib/* org.elasticsearch.bootstrap.Elasticsearch -d -Epath.conf=/var/ZDH/multiService/run/1176-elasticsearch-elasticsearch-elasticsearch -p /var/ZDH/multiService/run/1176-elasticsearch-elasticsearch-elasticsearch/elasticsearch-elasticsearch-elasticsearch.pid`

the 'top' prints:  
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND  
**12547 elastics 20 0 479g 42g 23g S 418.1 33.7 1919:26 java**  
32994 root 20 0 0 0 0 D 1.3 0.0 0:31.27 flush-8:128  
3571 root 20 0 0 0 0 D 1.0 0.0 5:09.28 jbd2/sdi1-8  
3577 root 20 0 0 0 0 S 1.0 0.0 6:49.30 jbd2/sdl1-8

why elasticsearch used 42g, far greater than 32G ?

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [August 3, 2017, 2:11am UTC](https://discuss.elastic.co/t/why-elasticsearch-use-so-much-os-memory/92001/2 "2017-08-03T02:11:52Z")

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