In my Ubuntu 11.10 VPS, Before I run the jar file:

# free -m
             total       used       free     shared    buffers     cached
Mem:           256          5        250          0          0          0
-/+ buffers/cache:          5        250
Swap:            0          0          0

Run a jar file that limited to maximum of 32M memory:

java -Xms8m -Xmx32m -jar ./my.jar

Now the memory state as follows:

# free -m
             total       used       free     shared    buffers     cached
Mem:           256        155        100          0          0          0
-/+ buffers/cache:        155        100
Swap:            0          0          0

This jar occupied 150M memory.

And I can't run any other java command:

# java -version
Error occurred during initialization of VM
Could not reserve enough space for object heap
Could not create the Java virtual machine.

# java -Xmx8m -version  
Error occurred during initialization of VM
Could not reserve enough space for object heap
Could not create the Java virtual machine.

I want to know why the -Xmx parameter does not take effect?

How can I limit the jar file using the memory?