[SOLVED] Servlet memory management

[chilljava]

I have a simple servlet with service and init method. i run this servlet in tomcat server. when i view memory usage using Jrockit mission control i observe the memory keeps going up and comes down after some time(when GC is called). the memory graph looks like a steps going up and fall down after some time and again goes up. I do not have any code in service or init method, so why the memory goes up and down, rather than staying stable as a straight line. i use JRockit JVM with -Xgcprio:throughput GC setting. Please help.