Measure peak memory consumption (of a Java Application) at runtime?

Question

I have to run a couple of java services on my machine to obtain a certain dev environment (and get my not-java-related work done)

java -Xmx400m -jar foo-app/target/foo-app-SNAPSHOT.jar
java -Xmx250m -jar bar-app/target/bar-app-SNAPSHOT.jar
...

To not run out of memory, I need to limit the memory usage. The default (512m afaik) ist too high for my machine so I lowered them somewhat (on a wild as guessing basis). Except for one, where I learned the hard way (crashed, even freezes, and thankfully some .pid error files left behind in the project folder...), that I better settle a little higher:

java -Xmx800m -jar doo-app/target/doo-app-SNAPSHOT.jar

Question : is there a way, to track memory usage of a certain app over time?

By some java command line parameter or even with ps -ae , htop or similar? (thus not fiddling in the source itself, remap garbage collectors, etc, etc)

I see plenty of numbers, but figuring out which belong to which java project running, and what could roughly indicate me a proper peak memory consumption (in a -Xmx___m sense)... I have no idea.

I work under Ubuntu-MATE 16.04, x64.

Answer 1

The best way to analyze memory consumption is a profiler. In your jdk there comes the jvisualvm profiler, which is absolutely sufficient for this task. A (lengthy) tutorial can be found here: https://engineering.talkdesk.com/ninjas-guide-to-getting-started-with-visualvm-f8bff061f7e7

Other approaches are basically shotgun-style -reduce the xmx and then generate load in the system and see if it runs oom. If you do NOT have a straight controll flow you have no way to predict the used memory.