Given a 64-bit processor with its enormous address space, compare the advantages and disadvantages of hierarchical page tables and inverted page tables.

a) How many levels of page table (index into index...) are required in a 64-bit system?

b) How big are the respective levels of index and actual page table?

c) Are these page tables maintained on a per-process or global basis or is it partly one and partly the other?

d) When does the page table get updated for a process?

e) Can a process run unless each of its page references is mapped to a physical frame?

f) How do inverted page tables reduce the memory required to maintain page to frame mapping for a 64 bit system?

g) Explain the issue posed by shared memory for inverted page tables, where there is presumably one entry per process per frame.

h) What is the problem posed in updating the inverted page table when processes switch context?

i) What other structure has to maintained to address this?