odd memory_usage() results

[eluser]WanWizard[/eluser]
I hope someone can explain this issue I have with memory_usage(), as displayed by the profiler.

We have a small team developing on an application. Although the actual hardware used differs from developer to developer (all laptops though), they all use an up-to-yum version of Fedora 11 to develop on.

I have checked, checked, and double checked, but the Apache, MySQL and PHP versions are identical, and so are the php.ini, httpd.conf and the my.cnf files.

Source is checked out of our subversion server, so apart from the bit they're working on, code in all development enviroments is identical as well. Same goes for the contents of the development database (we use a central test set to load it).

Now, the issue is that on some machines, memory usage reported is 2Mb to 3Mb higher than on others when requested exactly the same URL (a controller that nobody is working on). Percentage wise, we're taking about 25-40% more memory used.

Who has a clue to what's going on here, or how to determine what's going on?