how to check heap size allocated for jvm by linux

Question

I have apache-tomcat as my web server. I want to check what heap size is allocated for jvm by linux. Also from where, I can modify it.

Answer 1

You can easily check the heap size memory allocation using JConsole, if you have a path to your jre/jdk set up correctly on the system you should be able to start it with command jconsole from anywhere.

For managing your heap memory allocation you can have a look here: http://javahowto.blogspot.com/2006/06/6-common-errors-in-setting-java-heap.html

Answer 2

A simple way on Linux is to run the following:

ps -ef |grep tomcat

Look for the starting and maximum JVM memory:

-Xms1024m -Xmx4096m

In this case it is allocating 1G on startup and the Maximum is 4G.

Answer 3

The heap size used by Tomcat is defined in its configuration.

This is the place where you can both check and change it.

If you're unsure about where this configuration is saved, I'd suggest looking at the Tomcat documentation where this is explained together with all configuration values.

Answer 4

If you need more information from the server but cannot log into it interactively (or don't have a GUI or JMX set up etc) you can include javamelody in your POM file/libs and it will create a page at host:8080//monitoring with all kinds of good information, including heap size, GC statistics and permgen size.

This is NOT a safe thing to leave running in a production environment - if you need it all the time at least lock it down!