Re: Max heap size when using -XX:MaxRAMPercentage
Christopher, thanks for your reply. Answers inline. > > What I see in the profiler is Max Heap Size 310378496 B, which is only 0.28 > > GiB. > > This is probably the maximum size of the /used/ heap. Can you confirm that? Nope. Netbeans profiler says: Max Heap Size 310378496 B, Max Used Heap 261052168 B > Try running your application without *any* memory parameters and run it > through a reasonable exercise. Then look at everything with your > profiles *and also* make sure you look at the OS's report of the > allocated memory for the process. That will give you a sense for how > much "native memory" versus heap memory your application actually needs. > You may find that the native memory requirements are roughly the same > size as the Java heap requirements. That means you can't even reasonably > approach a 50% heap size because you still need to be about to run the > OS which takes a bit of memory. I'll try that now. I've seen people recommending up to 80% RAM though: https://dev.to/focusedlabs/the-no-nonsense-guide-to-jvm-14-memory-on-kubernetes-508m - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
Re: Max heap size when using -XX:MaxRAMPercentage
Martynas, On 11/11/20 10:20, Martynas Jusevičius wrote: 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. This is probably going to be a problem for you. The heap you are specifying is the Java heap only. There are all kinds of other memory spaces the JVM needs in order to run. You may find that 75% of the available RAM is so large that you can't do other things. 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. This is probably the maximum size of the /used/ heap. Can you confirm that? 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? It's probably the 2.78G. You are likely getting "Cannot allocate memory" errors because the JVM is trying to allocate non-heap memory. Try running your application without *any* memory parameters and run it through a reasonable exercise. Then look at everything with your profiles *and also* make sure you look at the OS's report of the allocated memory for the process. That will give you a sense for how much "native memory" versus heap memory your application actually needs. You may find that the native memory requirements are roughly the same size as the Java heap requirements. That means you can't even reasonably approach a 50% heap size because you still need to be about to run the OS which takes a bit of memory. Hope that helps, -chris - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
Max heap size when using -XX:MaxRAMPercentage
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 - To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
