Test #3

Question 1

Deadlock

Answer 1

Condition where a set of 2 or more procs are blocked and waiting for something from another proc in that set to do

Question 2

4 Necessary Conditions for Deadlock

Answer 2

1. mutex
2. hold and wait
3. no preemption (cant take away resource I have)
4. circular wait

Question 3

4 Ways to deal with deadlock

Answer 3

1. Ignore it
2. detect and recover
3. prevent
4. avoid

Question 4

To prevent deadlock, which condition should you prevent

Answer 4

4. circular wait

Question 5

How does detect and recover work

Answer 5

• delete one process and reallocate resources
• rollback
• tough decision will have to be made

Question 6

How does Prevent work

Answer 6

Remove one of the four conditions that cause deadlock
1) Mutex BAD - lost update
2) hold and wait INEFFICIENT - get all resources before you start
3) no preemption BAD
4) Circular wait BEST - put priority on resources and allocate accordingly

Question 7

Know the Bankers algorithm safety algorithm

Question 8

R -> P

Answer 8

resource allocated to process

Question 9

P -> R

Answer 9

Process requesting resource

Question 10

when you find a cycle in a resource allocation graph

Answer 10

deadlock

Question 11

easiest way to recover from deadlock

Answer 11

kill all processes

Question 12

Know the resource allocation graphs

Question 13

Know the seven state process state diagram

Answer 13

Start, ready, ready suspended, run, blocked, blocked suspended, exit

Question 14

Variable sized blocks/partitions

Answer 14

RAM partitions have varying size

Question 15

Fixed sized blocks/partitions

Answer 15

RAM partitions are equally sized

Question 16

Internal Fragmentation

Answer 16

small slivers of unusable RAM between processes in fixed sized partitions

Question 17

External Fragmentation

Answer 17

small slivers of unusable RAM between processes in variable sized partitions

Question 18

Job placement first fit

Answer 18

first slot

Question 19

Job placement worst fit

Answer 19

free space that is largest

Question 20

Job placement next fit

Answer 20

first fit AFTER previous job

Question 21

Job placement best fit

Question 22

Non-swapping

Answer 22

RAM only, logarithmic dmp graph

Question 23

swapping

Answer 23

swapping between RAM and disk, bell curve dmp graph

Question 24

Know how paging memory management works

Question 25

Logical address

Answer 25

page # , offset

Question 26

Physical address

Answer 26

location in RAM

Question 27

Relocatable code

Answer 27

Code that can be run from any spot in memory (references to data are variable)

Question 28

Page Table

Answer 28

Each process has one page table, which frame is loaded from RAM

Question 29

Frame Table

Answer 29

1 per system; holds information about which frames are mapped

Question 30

Memory Management Unit (mmU)

Answer 30

Translates logical address into physical address

Question 31

Demand Paging

Answer 31

putting pages in when they need it (not loaded)

Question 32

Thrashing

Answer 32

situation where the system spends more time swapping pages between RAM and disk than executing actual process, leading to severe performance degradation - represented on tail end of swapping memory dmp graph

Question 33

Memory compaction

Answer 33

In external fragmentation, shifting all the processes up, moving all free space to bottom

Question 34

FIFO page replacement

Answer 34

First in first out

Question 35

LRU page replacement

Answer 35

Least Recently Used; time stamp and lots of overhead (slow)

Question 36

Optimal page replacement

Answer 36

theoretical; frame that will be referenced longest time in the future

Question 37

LRU-approx page replacement

Answer 37

Contains dirty bit and ref bit

Question 38

Dirty Bit:

Answer 38

only set if you write to FRAME - local copy diff from DB - ex: x++;

Question 39

Ref Bit:

Answer 39

reading or writing to PAGE = 1 - all are cleared after sweeping time interval

Question 40

if ref bit = 1...

Answer 40

page has been referenced since last clear

Question 41

LRU Approx Ref and Dirty Bit combo rankings

Answer 41

#1) 0 0 #3) 0 1 #2) 1 0 #4) 1 1

Question 42

Global Frame Policy

Answer 42

Look at whole frame table to kick someone out

Question 43

Local Frame Policy

Answer 43

Set distinct # of frames and determine if kick out

Question 44

Belady's Anomoly

Answer 44

Anomaly where increasing number of page frames results in an INCREASE in number of page faults

Question 45

A process is divided into

Answer 45

pages

Question 46

Page Fault

Answer 46

special interrupt that says somebody was running and made a reference to some part of program that is not loaded in memory

Question 47

RAM is divided into

Answer 47

frames

Question 48

when do we use replacement algorithm

Answer 48

when RAM is full