Self
Test - Chapter Eight
CIS343
(1-9) Dynamic run-time
address translation is considered a fundamental breakthrough in memory
management. It can be described thus:
1. All memory references
within a process are _____.
2. These are dynamically
translated into _____ at run time.
3. T/F: Therefore, a process can
occupy different regions of memory at different times during the course of
execution.
4. T/F: This, in turn, means that a
process should never be swapped in and out of memory during execution.
5. T/F: As a consequence, a process
can be broken into a number of pieces.
6. T/F: But, during execution, these
pieces must be contiguous to each other when transferred to main memory.
7. In addition, during
execution it is _____ [necessary, not necessary] for all the pieces of a
process to be in main memory.
8-9. The two pieces of a process
that must be in main memory in order for execution to proceed are the piece
that holds _____ and the piece that holds _____.
10-11. These ideas are exploited by
what two memory management techniques?
12. The portion of a process
that is actually in memory at any given time is called the _____ of that
process.
13. This breakthrough has two
important implications. First, a
process may now be _____.
14. And, second, the operating
system can increase the _____.
15. This, in turn, increases
efficiency because it increases the likelihood that at any given time at least
one process will be in the _____.
16. The reason more processes
can be maintained in memory is because _____.
17. During execution, then, a
process resides partly in main memory and partly _____.
18. But to the programmer or
user it appears that the process is sitting in main memory at all times. Since appearance does not exactly match
reality, this gave rise to the term _____ memory.
19-21. When paging is implemented
the logical address (the address referenced by a process) is translated into a
_____ address, consisting of a _____ and an _____.
22-24. This, in turn, is translated
into a _____ and an _____, which is used to compute the _____ address.
25. For this to work a
correlation of pages to frames must be available. This is called the . . .
26. Since not all pages of a
process are in main memory, sometimes the page the process needs to access is
on disk. In that case a _____ occurs.
27. If virtual memory usage is
not managed well, the processor can spend most of its time moving things to and
from disk, instead of performing useful processing. This phenomenon is called . . .
28. In most systems there is one
page table per _____.
29. The loss of usable memory to
page tables is sometimes called . . .
30. If a process has a very
large address space the resulting page table will also be very large. To address this problem, the page table is
sometimes kept in . . .
31. T/F: In that case it is possible
for two page faults to occur on a single memory access.
32. An alternative to the two
level paging system is to use an _____ page table.
33. With this scheme there is
one entry in the page table for each . . .
34. T/F: Thus a fixed amount of
memory is used for the page table, regardless of the size of virtual memory
addressed by the active processes.
35-36. Still, every virtual memory
reference can cause two physcial memory accesses - one to fetch the _____ and
one to fetch the _____.
37-39. To overcome this problem,
most virtual memory systems make use of a special _____ containing the most
recently used page table entries, called a _____.
40-41. When virtual memory is
implemented via paging, the page table entry for each page must have a _____
bit and a _____ bit.
42. To prevent memory access
slowdowns due to search of the TLB, the processor is equipped with hardware
that allows it to interrogate _____ a number of TLB entries when seeking a
match.
43. This technique is known as .
. .
44-45. In a system with both TLB
and cache, the maximum number of lookups that can occur on one memory reference
is _____ and the minimum is _____.
(46-51) Listed below are
considerations relevant to the choice of page size. Identify which argue for larger, and which for smaller page size.
46. Desire to decrease internal
fragmentation.
47. Desire to decrease size of
page tables
48. Desire to increase the
number of page frames available to a process
49. Physical characteristics
(rotational) of most secondary storage devices.
50. Desire to decrease the
number of page faults by appeal to principle of locality
51. Maintain ratio of total
amount of memory referenced by TLB to memory size of processes by having each
TLB entry refer to a larger portion of memory.
(52-53) Identify these
programming techniques which tend to decrease the locality of reference within
a process.
52. Many small program and data
modules are scattered over a relatively large number of objects in a relatively
short period of time.
53. Abrupt changes in
instruction stream and scattered memory references
(54-55) Identify these fetch
policies:
54. A page is brought into main
memory only when a reference is made to a location on that page.
55. Pages are brought in
anticipating their later use.
56-57. Under segmentation the
virtual address is translated into a _____ and an _____.
58-60. This is then translated into
a _____ and an _____ which, in turn, yields the _____.
61-63. Under segmentation/paging
the virtual address is translated into a _____, a _____, and an _____.
64. Frame
locking: When a
frame is locked the page currently stored in that frame may not be _____.
65. Much of the _____ is held in
locked frames.
(66-69) Identify these
replacement policies:
66. Replace the page whose used
bit is 0 (resetting that bit as the page is passed over)
67. Replace the page for which
the time to next reference is the longest.
68. Replace the page which has
not been referenced for the longest time.
69. Replace the page which has
been in memory the longest.
70. If there are n pages in the set to be considered for replacement,
what is the maximum number of pages, under Clock, that may be scanned before
a page is found to be replaced?
71. In the modification of Clock
(modClock) using two bits (u - used; m - modified), there are 4
possible combinations of u & m: 0-0, 0-1, 1-0, 1-1. Which combination is chosen during Step #1 of modClock?
72. Which combination is chosen
during Step #2 of modClock?
73. If Step #2 fails, Step #3
involves . . .
74. How is it possible for a
page to be modified, but unused?
75. T/F: Since at no step do we
choose pages with the 1-0 or 1-1 combination, any page that has that bit combination
never gets replaced.
76. The Optimal
page
replacement strategy has been proven to be the best.
77. There are no operating
systems which use the Optimal page replacement strategy.
(78-79) Identify these
resident set management policies:
78. Give a process a fixed
number of pages within which to execute.
79. Allow the number of page
frames allocated to a process to change over the lifetime of a process.
(80-81) Identify these scope
of replacement policies:
80. Choose only among the
resident pages of the process that generated the page fault to find a page to
replace.
81. All unlocked pages in memory
are candidates for replacement, regardless of which process they belong to.
82. Among the 4 possible
combinations of resident set management and replacement policies, which one is
not possible?
83. The set of pages that a
process is accessing over a period of time is known as its . . .
(84-86) Complete these
sentences which describe how the working set of a process can be used to guide
a strategy for determining resident set size.
84. Monitor the _____ of each
process.
85. Periodically _____ the
resident set of a process those pages that are not in its working set.
86. A process may execute only
if _____ in main memory.
(87-89) Complete these
sentences which state three problems with the working set strategy.
87. The past . . .
88. A true measurement of the
working set of each process is . . .
89. The optimal value of
D(the window size) is . . .
90. What measurement may be used
as an approximation for determining whether or not the working set of a process
is in main memory?
91. A problem with this approach
is that during interlocality transitions, the rapid succession of page faults
causes the _____ of a process to swell.
(92-93) Identify these
cleaning policies:
92. A page is written out to
secondary memory only when it is selected for replacement.
93. Modified pages are written
before page frames are needed, so that pages can be written out in batches.
94. Good load control is
critical to effective memory management.
If too few processes are resident, it could lead to _____.
95. Why?
96. If too many processes are
resident, it could lead to _____.
97. Why?
Word Bank
- Chapter 8 Self Test
CIS343
Answers to questions #1-25.
A. apparent
B. correlation coefficient
C. degree of multiprogramming
D. dynamic addresses
E. frame number
F. false
G. the function “main”
H. imaginary
I. imaginary page
J. in ROM
K. in the registers
L. larger than main memory
M. logical addresses
N. memory augmentation
O. memory dispersal
P. memory portion
Q. more processes have finished EE. private number
R. necessary FF. public
number
S. the next data location to be accessed GG. Ready state
T. true HH. real
U the next instruction to be fetched II. resident
set
V not necessary JJ. Running
state
W. offset KK. segmentation
X. on a CD LL. speed of
the processor
Y. on disk MM. static
addresses
Z. only a portion of each process is actually in
memory
AA. paging NN. the
variable declarations
BB. page number OO. virtual
CC. page table PP. virtual
page
DD. physical addresses QQ. virtual
reality
Answers to questions #26-51, except 44 &
45.
A. address memory
B. associative mapping
C. binary
D. cache
E. cold fusion
F. false
G. cold storage
H. data
I. decimal
J. disk fault
K. hexadecimal
L. intentional
M. inverted
N. larger
O. memory access
P. memory location
Q. memory loss
R. memory reference
S. memory table
T. true
U. modified
V. oblong
W. page fault
X. page table entry
Y. process
Z. real memory page frame
AA. recency chart
BB. resident
CC. a senior moment
DD. simultaneously
EE. smaller
FF. suspected memory references KK. table memory
GG. suspect identification LL. thrashing
HH. suspects MM. translation
lookaside buffer
II. swapping NN. virtual
address
JJ. table fragmentation OO. virtual
memory
Answers to questions #52-77, except 70-72.
A. array
reference
B. base
address
D. Clock
D. demand
paging
E. FIFO
(first in, first out)
F. false
G. frame
number
H. generating
a page fault
I. global
variables
J. kernel
of the OS
K. local
paging
L. location
fetch
M. longest
page
N. longest
replacement
O. longest
segment
P. LRU
(least recently used)
Q. modified
R. multithreaded
applications
S. offset
T. true
U. OO
techniques
V. optimal
W. the OS
would not allow it to be used
X. page
number
W. prepaging
Y. the
program decided not to use it
Z. real
address
AA. a
repetition of Step #1, and then Step #2, if necessary
BB. a
repetition of Step #1 only
CC. replaced
DD. segmentation
fault
EE. segment
number
FF. sensitive
information
GG. subroutine
calls
HH. virtual
number
II. virtual
page
JJ. used
KK. the used
bit gets reset during Step #2 of modClock
LL. the user
decided not to use it
MM. user
profile
NN. Zero
replacement
Answers to questions #78-97.
A. access
set RR. resident replacement policy
B. add to SS. resident set
C. all its
pages are TT. resident set size
D. all
processes are blocked UU. the size of the process
E. blocked
time VV. spring cleaning
F. demand
cleaning WW. starvation
G. divisible
by two XX. there is room
H. does not
always predict the future
I. dynamic
frame policy YY. time spent on the ReadyQ
J. dynamic
page policy ZZ. too many jobs on the ReadyQ
K. equal to
50 A1. unknown
L. excessive
swapping B2. vacuum cleaning
M. execution C3. variable allocation, global scope
N. fixed
allocation, global scope D4. variable allocation, local scope
O. fixed
allocation, local scope E5. variable allocation policy
P. fixed allocation policy F6. working set
Q. fixed
frame policy
R. fixed
page policy
S. frequent
faulting
T. global
replacement policy
U. greater
than 50
V. impractical
W. inadequate resident size for resident processes
X. is past;
don’t worry about it
Y. its
working set is
Z. lack of
communication
AA. less
than 50
BB. local
replacement policy
CC. loneliness
DD. modify
with
EE. non-resident
replacement policy
FF. number
of instructions
GG. the
number of page faults
HH. overcrowding
II. page
allocation policy
JJ. page
fault frequency
KK. pages
will not be used again
LL. postcleaning
MM. precleaning
NN. processing
time
OO. process
replacement policy
PP. progress
QQ. remove from