HEAP SIZE

Heap size

The allocation of memory for the JVM is specified using -X options when starting Resin (the exact options may depend upon the JVM that you are using, the examples here are for the Sun JVM).

JVM option passed to Resin	Meaning
-Xms	initial java heap size
-Xmx	maximum java heap size
-Xmn	the size of the heap for the young generation

Resin startup with heap memory options

unix> bin/httpd.sh -Xmn100M -Xms500M -Xmx500M win> bin/httpd.exe -Xmn100M -Xms500M -Xmx500M install win service> bin/httpd.exe -Xmn100M -Xms500M -Xmx500M -install

It is good practice with server-side Java applications like Resin to set the minimum -Xms and maximum -Xmx heap sizes to the same value.

For efficient garbage collection, the -Xmn value should be lower than the -Xmx value.

Heap size does not determine the amount of memory your process uses

If you monitor your java process with an OS tool like top or taskmanager, you may see the amount of memory you use exceed the amount you have specified for -Xmx. -Xmx limits the java heap size, java will allocate memory for other things, including a stack for each thread. It is not unusual for the total memory consumption of the VM to exceed the value of -Xmx.