>> frame must be evicted. Describe your code for choosing a frame to
>> evict.
+>> When a process P obtains a physical frame that was previously used
+>> by a process Q, how do you adjust the page table (and any other
+>> data structures) to reflect the physical frame Q no longer has?
+
>> Explain your heuristic for deciding whether a page fault for an
>> invalid virtual address should cause the stack to be extended into the
>> page that faulted.