How to monitor memory usage and allocation for Java?
Sandra Bernspang (15●1●5●8)
| asked Oct 08 '12, 10:38 a.m.
JAZZ DEVELOPER edited Oct 08 '12, 10:41 a.m.
Is there any way I can monitor how much memory is allocated to Java and more importantly, how much memory is being used by Java? Is there a built-in monitor? If not, what external tool would you recommend?
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4 answers
You can turn on JMX monitoring at the application server level. Here are the java JVM options I use to turn it on (no password...)
-Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -Dcom.sun.management.jmxremote.port=1099 I use this with both WebSphere application server as well as Tomcat successfully in all versions of CLM. I have integrated this with logicmonitor.com's SaaS monitoring very successfully to show online dashboards of what is going on in the server. Here is a demo that we use at oncloudone.net: https://oncloudone.logicmonitor.com/santaba/uiv2/onegadgets/index.jsp?c=oncloudone&u=demo&p=demo Username: demo Password: demo All too often people forget to tune their Java settings and end up throwing a lot more hardware (CPU power) when all that is needed is a few JVM tweaks to prevent the garbage collection from running too often. |
For high level heap usage, you can simply look into the Jazz application admin page, eg: <host>/jts/admin: it will show the VM memory usage.
Another useful JVM option is to enable verbose GC (adding option -verbose:gc on JVM command line), it will log GC activity, and there are tools helping visualize it and notice memory levels, GC pauses etc... JMX (suggested above) is another good option. |
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Comments
Are you talking about java allocation by the server? I guess I need a little more information on your specific use case.
I'd like to understand how much memory is being used by Java. I've set the Java heap size to 6 GB, but I'd like to understand if that is actually too much or too little to get good performance. I was thinking that some statistics on how much memory is actually used while the server is up and running, I could determine that.
And to clarify, I don't refer to how much is allocated, though such statistics would also be interesting to look at.