Hi,
I am attempting to make my webapps that run in Tomcat to take
advantage of the Docker container-specific JVM options such as
-XX:MaxRAMPercentage:
https://www.eclipse.org/openj9/docs/xxinitialrampercentage/
TL;DR It allows specifying JVM heap as % of the container memory limit
rather than using the default 25%.
Running tomcat:9.0.39-jdk11, what I did is specify
CATALINA_OPTS=-XX:MaxRAMPercentage=75
which should use 75% of the container memory limit which is 3.702GiB
in this case.
So I login into the container and execute ps aux to see Tomcat's
command arguments:
/usr/local/openjdk-11/bin/java
-Djava.util.logging.config.file=/usr/local/tomcat/conf/logging.properties
-Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager
-Djdk.tls.ephemeralDHKeySize=2048
-Djava.protocol.handler.pkgs=org.apache.catalina.webresources
-Dorg.apache.catalina.security.SecurityListener.UMASK=0027
-XX:MaxRAMPercentage=75.0 -Duser.timezone=Europe/Copenhagen
-Dignore.endorsed.dirs= -classpath
/usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar
-Dcatalina.base=/usr/local/tomcat -Dcatalina.home=/usr/local/tomcat
-Djava.io.tmpdir=/usr/local/tomcat/temp
org.apache.catalina.startup.Bootstrap start
If I replace "org.apache.catalina.startup.Bootstrap start" with
"-XshowSettings:vm -version" and run, this is what I get:
Max. Heap Size (Estimated): 2.78G
Using VM: OpenJDK 64-Bit Server VM
Where 2.78G is 75% of 3.7GiB -- so far so good, the MaxRAMPercentage
setting seems to have worked here.
But I'm still getting "Cannot allocate memory" exceptions that kill
the container when importing large datasets. So I attached a profiler.
What I see in the profiler is Max Heap Size 310378496 B, which is only 0.28 GiB.
So how much max heap does my webapp have access to -- is it 2.78G or
0.28G? If it's 0.28, why? How do I enforce the 75% RAM setting for the
webapp?
Martynas
atomgraph.com
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