mjhjmtu

I'm tuning my elastic search cluster and see that the memory usage doesn't line up.

Running "free" on my instance:

free
 total used free shared buff/cache available
Mem: 30881324 17072320 238216 49736 13570788 13313528
Swap: 0 0 0

We see that there is 30GB on the machine.

ES was tuned to use 50% of available memory (or max 30GB for oop reasons)
And I can verify here the -Xms and -Xmx flags are set to 15078m:

/bin/java -Xms15078m -Xmx15078m -XX:+UseConcMarkSweepGC -XX:CMSInitiatingOccupancyFraction=75 -XX:+UseCMSInitiatingOccupancyOnly -XX:+AlwaysPreTouch -server -Xss1m -Djava.awt.headless=true -Dfile.encoding=UTF-8 -Djna.nosys=true -XX:-OmitStackTraceInFastThrow -Dio.netty.noUnsafe=true -Dio.netty.noKeySetOptimization=true -Dio.netty.recycler.maxCapacityPerThread=0 -Dlog4j.shutdownHookEnabled=false -Dlog4j2.disable.jmx=true -XX:+HeapDumpOnOutOfMemoryError -Des.path.home=/usr/share/elasticsearch -Des.path.conf=/etc/elasticsearch -Des.distribution.flavor=default -Des.distribution.type=rpm -cp /usr/share/elasticsearch/lib/* org.elasticsearch.bootstrap.Elasticsearch -p /var/run/elasticsearch/elasticsearch.pid --quiet

But when running "top" we see a different story.

%MEM is at 59% , many times will show 85% or more (triggering nagios alerts):

 PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
24366 elastic+ 20 0 54.9g 17.5g 1.6g S 267.7 59.3 1849:57 java