Hi

> Description :
> right after system(tomcat) is started, the "top" command show 
> that tomcat process will use 210M memory, the heap size 
> (using Jprofiler) is 58m/20m(total/used). there is a 150M gap 
> between total process memory size and java heap size.

There needs to be some memory for the JVM as well as your classes.
Furthermore GCs may keep two copies of the youngest generation part of the
heap.

>  So my questions are:
> 1,  what is the difference between java process memory size  
> and java heap size ? why can it be 150M in right after tomcat 
> is started ?
> 2,  why the gap between top can heap can grows from 150M to 
> 320M, where does 170M more memory gone ?

I assume it was needed in between.
However, memory allocated by the JVM not not neccessarily lost. Not being
used that may be swapped out.

Regards,
  Steffen

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