Paging in free memory (adding a mapping) is cheap (no need to flush). Removing a mapping is expensive (need to flush). Also, processes have their own (mostly) i

Paging in free memory (adding a mapping) is cheap (no need to flush). Removing a mapping is expensive (need to flush). Also, processes have their own (mostly) independent page tables. I don't think it would be reasonable accounting, when paging-in is cheap, but only if there is no need to page out (available free memory). Especially when trying to argue that paging out is zero-cost.