15 - Address Translation

Limited direct execution

memory virtualizing takes a similar strategy known as _ _ _ for efficiency and control

Hardware support

in memory virtualizing, efficiency and control are attained by hardware support

Flexibility

allow process to be able to use their address space in whatever way they like

Physical address

address translation, hardware transforms a virtual address to a _ _

Physical address

the desired information is actually stored in a _ _

Manage memory

the OS must _ _, to judiciously intervene

Contiguously

user’s address space is placed _ in physical memory, current assumptions (1)

Not Too big

address space size is _ _ _, less than the size of the physical memory, current assumptions (2)

Same

address space size for all processes are the _, current assumptions (3)

Address Space Relocation

the process’ view of its virtual address space is from 0 to 16KB

Dynamic Relocation

program is written and compiled as if its loaded at address zero

Virtual address + base

set the base register a value, physical address is equal to

Not greater than bound, not negative

every virtual address must _ be _ _ _ and _ _

Kernel and User Mode

processor modes, determined through a processor status word

Base Register and Bounds Register

2 memory management unit

Kernel mode

changing the base and bounds registers should be allowed only in _ _

Exceptions

processor should be able to generate _ during illegal memory access

Base and bounds approach

issues that the OS must address for Dynamic Relocation, the OS must take action to implement _ _ _ _

Running

finding space for address space in physical memory, maintain a free list

Terminated

reclaiming the memory for use by other processes

Switch occurs

saving and storing the base-and-bounds register pair for each process since we only have one pair per core

Switch occurs

when a process is blocked, it can easily be moved to a different location

Privileged instructions

at boot time, the OS must set exception handlers using _ _

Find a room

OS Issues, when a process starts running

Free list

a list of the range of the physical memory which are not in use

Put the memory back

OS Issues, when a process is terminated

Save and restore

the OS must _ _ _ the base-and-bounds pair

Internal fragmentation

not all allocated space is used, other issues with dynamic relocation