Can you run the app with enough memory and check process memory usage
from `oc rsh`? Perhaps it will give more insight.
The container is not running a separate OS. It is just the process you
are starting within that container and the libraries it loads. And any
additional processes it spawns. So standard memory profiling techniques
should apply within the container.
I know that people are looking at ways to decrease java footprint for
small apps. You know the java modularization effort. graalvm as another
example. Presently situation is not ideal for such use cases IMO. I
trust that things will improve over time though.
Karl Nicholas wrote on 06/13/18 00:19:
I’m messing around with*JAVA_MAX_MEM_RATIO* to see about saving on
memory. With every setting I also adjust the container memory so that I
get the following JVM parameters.
exec java
-javaagent:/opt/jolokia/jolokia.jar=config=/opt/jolokia/etc/jolokia.properties
-Xms512m -Xmx512m -XX:+UseParallelGC -XX:MinHeapFreeRatio=20
-XX:MaxHeapFreeRatio=40 -XX:GCTimeRatio=4
-XX:AdaptiveSizePolicyWeight=90 -XX:MaxMetaspaceSize=256m
-XX:ParallelGCThreads=2
-Djava.util.concurrent.ForkJoinPool.common.parallelism=2
-XX:CICompilerCount=2 -XX:+ExitOnOutOfMemoryError -cp . -jar
/deployments/opinions-web-swarm.jar
The “*Xms512m -Xmx512m*” are, to me, the important ones. So, if I set
the *container memory to 1Gb and the JAVA_MAX_MEM_RATIO to 50% *(the
default), then I get the above JVM settings and my application works fine.
If I set the *container memory to 854Mb and the JAVA_MAX_MEM_RATIO to
60%*, then I get the above settings and my application, so far, works fine.
If I set the *container memory to 732Mb and the JAVA_MAX_MEM_RATIO to
70%*, then I get the above JVM settings and my application *CRASHES.*
So, something outside the JVM needs more 732-512 or 220Mb (and less than
342, I’m guessing 256?) of memory to run the JVM? Does the OS inside
need that much? The image is a wildfly-11-swarm image with EJB/JSF/REST
and a few things built inside of openjdk18-openshift:latest image.
Is there some way to configure or know how much the openjdk18-openshift
redhat supplied image needs for memory outside of the JVM settings?
Should I look into rebuilding it myself if I need to control the memory
usage?
Thanks.
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