The swapper actually does not distinguish whether a page is of text or is of data.  The swapping takes place in chunks of pages.  Only some of the pages of a process may get swapped out depending upon the need for new physical pages and last access times of the pages.  I have presented a very simplified view of the swapping since the entire swapping mechanism is very difficult to grasp in its entirety.  For those who wish to actually deal with UNIX source code, a further study will be required whether it is Process management OR Memory management OR File management.

MLS Shastry