Mon Apr 5 20:02:52 CEST 2010

How much memory is a process using?

RSS:  resident set size

All resident pages.

VSS:  virtual set size

All mapped memory.  Also includes mmapped files.

One thing I never understood is how shared memory fits in this
picture.  Also, when a process forks and memory doesn't get copied if
it's not modified, how do we know that?

The `pmap' utility gives memory usage per shared library.