A way to determine a process's “real” memory usage, i.e. private dirty RSS?

Question

Tools like \'ps\' and \'top\' report various kinds of memory usages, such as the VM size and the Resident Set Size. However, none of those are the \"real\" memory usage:

Answer 1

Use the mincore(2) system call. Quoting the man page:

DESCRIPTION
     The mincore() system call determines whether each of the pages in the
     region beginning at addr and continuing for len bytes is resident.  The
     status is returned in the vec array, one character per page.  Each
     character is either 0 if the page is not resident, or a combination of
     the following flags (defined in ):