We built an application that enables images to be loaded into a database through a servlet running on Tomcat. We have inconsistent behaivor when more than x number of people are loading images simultaneously. No doubt a memory allocation problem, but how can I measure it?

For example, I'd like to be able to create a graph showing the resources used against the number of people making uploads. I am using Linux and Tomcat/Apache.

Is there something like Windows Resource Kit Performance counters for Java and Linux platform??