Systems, Operating 6th ed.
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Chapter 7
Chapter 7 Memory Management
Operating Systems, 6th ed.
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Chapter 7
13. T / F In a memory system employing paging, the chunks of a process (called
frames) can be assigned to available chunks of memory (called pages).
True / False Questions:
1. T / F In a multiprogramming system, main memory is divided into multiple
sections: one for the operating system (resident monitor, kernel) and one for the
set of processes currently being executed.
2. T / F The task of subdividing memory between the O/S and processes is
performed automatically by the O/S and is called relocation.
14. T / F A memory system employing segmentation may suffer slightly from
external fragmentation and experience no internal fragmentation.
15. T / F A memory system employing segmentation consists of a number of user
program segments that must be of the same length and have a maximum
segment length.
Multiple Choice Questions:
3. T / F The practice in which a program and data are organized in such a way
that various modules can be assigned the same region of memory is called
overlaying.
4. T / F The concept of virtual memory is based on one or both of two basic
techniques: segmentation and paging.
5. T / F A major problem with the largely obsolete Fixed Partitioning memory
management technique is that of external fragmentation.
6. T / F The problem of internal fragmentation can be lessened in a system
employing a fixed-partition memory management scheme by using unequal size
partitions.
7. T / F In the Dynamic Partitioning technique of memory management, the bestfit placement algorithm is usually the best performer of the available algorithms.
8. T / F In the Dynamic Partitioning technique of memory management,
compaction refers to shifting the processes into a contiguous block, resulting in
all the free memory aggregated into in a single block.
9. T / F In the Dynamic Partitioning technique of memory management, the first-fit
placement algorithm scans memory from the location of the last placement and
chooses the first available block it finds that satisfies the request.
10. T / F The Buddy System is a reasonable compromise to overcome the
disadvantages of both the fixed and variable partition schemes.
11. T / F A physical memory address is a reference to a memory location
independent of the current assignment of data to memory.
12. T / F A memory system employing paging may suffer slightly from internal
fragmentation and experiences no external fragmentation.
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1. The task of subdividing memory between the O/S and processes is performed
automatically by the O/S and is called:
a. Protection
c. Memory Management
b. Relocation
d. All of the above
2. The concept of Memory Management satisfies certain system requirements,
including:
a. Protection
c. Physical organization
b. Relocation
d. All of the above
3. The practice in which a program and data are organized in such a way that
various modules can be assigned the same region of memory is called:
a. Overlaying
c. Relocation
b. Sharing
d. None of the above
4. The concept of virtual memory is based on one or both of two basic techniques:
a. Overlaying and relocation
c. Segmentation and
b. Segmentation and paging
partitioning
d. None of the above
5. A problem with the largely obsolete Fixed Partitioning memory management
technique is that of:
a. Allowing only a fixed
c. Internal fragmentation
d. All of the above
number of Processes
b. Inefficient use of memory
6. The problem of internal fragmentation can be lessened in systems employing a
fixed-partition memory management scheme by using:
a. Random size partitions
c. Unequal size partitions
b. Equal size partitions
d. None of the above
7. In the Dynamic Partitioning technique of memory management, the phenomenon
that results in unused blocks of memory outside of existing partitions is called:
a. Internal fragmentation
b. External fragmentation
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c. Compaction
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d. None of the above
8. In the Dynamic Partitioning technique of memory management, the placement
algorithm that chooses the block that is closest in size to the request is called:
a. Best-fit
c. Next-fit
b. First-fit
d. All of the above
9. In the Dynamic Partitioning technique of memory management, the placement
algorithm that scans memory from the location of the last placement and chooses
the next available block that large enough to satisfy the request is called:
a. Best-fit
c. Next-fit
b. First-fit
d. All of the above
10. A reference to a memory location independent of the current assignment of data
to memory is called a(n):
a. Relative address
c. Absolute address
b. Logical address
d. None of the above
11. An actual location in main memory is called a(n):
a. Relative address
c. Absolute address
b. Logical address
d. None of the above
12. The page table for each process maintains:
a. The frame location for
each page of the process
b. The page location for each
frame of the process
c. The physical memory
location of the process
d. None of the above
13. In a system employing a paging scheme for memory management, wasted space
is due to:
a. External fragmentation
c. Pages and frames of
b. Internal fragmentation
different specified sizes
d. None of the above
14. In a system employing a segmentation scheme for memory management,
wasted space is due to:
a. External fragmentation
c. Segments of different
b. Internal fragmentation
sizes
d. None of the above
15. In a system employing a segmentation scheme for memory management, a
process is divided into:
c. A number of segments
a. One segment per thread
which need not be of equal
b. A number of segments
size
which must be of equal
d. None of the above
size
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Fill-In-The-Blank Questions:
1. The task of subdividing memory between the O/S and processes is performed
automatically by the O/S and is called memory management.
2. The Memory Management task of moving the process image between different
areas of memory as required to support swapping is referred to as relocation.
3. The practice in which a program and data are organized in such a way that
various modules can be assigned the same region of memory is called
overlaying.
4. In almost all modern multiprogramming systems, memory is managed using a
sophisticated technique known as virtual memory.
5. The phenomenon, in which there is wasted space internal to a partition due to
the fact that the block of data loaded is smaller than the partition, is referred to as
internal fragmentation.
6. The problem of internal fragmentation can be lessened in system employing a
fixed-partition memory management scheme by using unequal size partitions.
7. In the Dynamic Partitioning technique of memory management, the process of
shifting processes so they occupy a single contiguous block in memory is called
compacting.
8. In the Dynamic Partitioning technique of memory management, the placement
algorithm that chooses the block that is closest in size to the request is called
best-fit.
9. In the Dynamic Partitioning technique of memory management, the phenomenon
that results in unused blocks of memory outside of existing partitions is called
external fragmentation.
10. Programs that employ relative addresses in memory are loaded using dynamic
run-time loading.
11. A compromise between the fixed and dynamic partitioning schemes for memory
management that employs aspects of both is called the Buddy System.
12. In a system that employs a paging memory management scheme, the page table
shows the frame location for each page of the process.
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13. In a system that employs a paging memory management scheme, the chunks of
a process can be assigned to available chunks of memory, which are called
frames.
14. A system that employs a segmentation memory management scheme makes
use of a segment table that provides the starting address of the corresponding
segment in main memory.
15. A system that employs a segmentation memory management scheme, the
program and its associated data are divided into a number of segments that need
not be of the same length.
Chapter 8 Virtual Memory
True / False Questions:
1. T / F In a system employing a memory management strategy that doesnt
require an entire process to be in main memory at one time, the portion of a
process that is actually in main memory at any given time is defined to be the
resident set of the process.
2. T / F The condition known as thrashing occurs when the majority of the
processes in main memory require repetitive blocking on a single shared I/O
device in the system.
3. T / F The modify (M) bit is a control bit in a page table entry that indicates
whether the contents of the corresponding page have been altered since the
page was last loaded into memory.
4. T / F A Page Fault occurs when the desired page table entry is not found in the
Translation Lookaside Buffer (TLB).
5. T / F One of the advantages to the programmer of virtual memory using
segmentation is that it simplifies the handling of growing data structures by
allowing the segment to grow or shrink as necessary.
6. T / F In a combined paging/segmentation system, a users address space is
broken up into a number of fixed-size pages, which in turn are broken up into a
number of segments.
7. T / F To achieve sharing in a segmentation system, it is possible for a segment
to be referenced in the segment tables of more than one process.
Operating Systems, 6th ed.
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Chapter 7
8. T / F Linux is an example of an operating system that does not provide virtual
memory.
9. T / F The fetch policy determines when a page should be brought into main
memory.
10. T / F The Least Recently Used (LRU) replacement policy replaces the page in
memory that has been referenced most recently.
11. T / F A global replacement policy considers all unlocked pages in main memory
as candidates for replacement, regardless of which process owns a particular
page.
12. T / F In a precleaning policy, modified pages are written to secondary memory
once they have been selected for replacement.
13. T / F SVR4 and Solaris systems use two separate schemes for memory
management, one for user processes and disk I/O, and another for kernel
memory allocation.
14. T / F Linux makes use of a two-level page table structure, consisting of a page
directory and a page table.
15. T / F Every W2K user process sees a separate 32-bit address space, allowing
4 GB of memory per process.
Multiple Choice Questions:
16. The type of memory that allows for very effective multiprogramming and relieves
the user of memory size constraints is referred to as:
a. Real memory
c. Main memory
b. Virtual memory
d. All of the above
17. The situation where the processor spends most of its time swapping process
pieces rather than executing instructions is called:
a. Paging
c. Thrashing
b. The Principle of Locality
d. None of the above
18. The situation that occurs when the desired page table entry is not found in the
Translation Lookaside Buffer (TLB) is called a:
a. TLB miss
c. Page fault
b. TLB hit
d. None of the above
19. The real address of a word in memory is translated from the following portions of
a virtual address:
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a. Page number and frame
number
b. Page number and offset
Chapter 7
c. Frame number and offset
d. None of the above
20. Segmentation has a number of advantages to the programmer over a nonsegmented address space, including:
a. Simplifying the handling of
c. Protection
growing data structures
d. All of the above
b. Sharing among processes
21. In a combined paging/segmentation system, a users address space is broken up
into a number of:
a. Segments or pages, at the
into variable-sized
segments
discretion of the
programmer
c. Variable-sized Segments,
which are in turn broken
b. Fixed-size pages, which
down into fixed-size pages
are in turn broken down
d. All of the above
22. Sharing is achieved in a segmentation system by:
the dispatcher main
a. Referencing a segment in
the segment tables of
memory area
c. Having a common data
more than one process
area that all processes can
b. Each process segment
share
table having a reference to
d. All of the above
23. A fundamental choice in the design of the memory-management portion of is:
c. an
O/S The algorithms employed
a. Whether or not to use
for various aspects of
virtual memory techniques
memory management
b. Whether to use paging,
d. All of the above
segmentation of a
combination of the two
24. The fetch policy that exploits the characteristics of most secondary memory
devices, such as disks, which have seek time and rotational latency is called:
a. Demand paging
c. Swapping
b. Prepaging
d. None of the above
25. The replacement policy that is impossible to implement because it would require
the O/S to have perfect knowledge of future events is called the:
a. Optimal policy
c. Clock policy
b. Least recently used (LRU)
d. None of the above
policy
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26. The replacement policy that chooses only among the resident pages of the
process that generated the page fault in selecting a page to replace is referred to
as a:
a. Global replacement policy
c. Variable replacement
b. Local replacement policy
policy
d. None of the above
27. The concept associated with determining the number of processes that will be
resident in main memory is referred to as:
a. A cleaning policy
c. Load Control
b. The page fault frequency
d. None of the above
28. In SVR4 and Solaris systems, the memory management scheme that manages
user processes and disk I/O is called the:
a. Paging system
c. Kernel memory allocator
b. Virtual memory manager
d. None of the above
29. The multi-level memory management scheme implemented in Linux was
designed to minimize large page tables and directories in which of the following
line of processors:
a. 16-bit X86 architecture
c. 64-bit Alpha architecture
d. None of the above
b. 32-bit Pentium/X86
architecture
30. The Windows 2000 virtual memory manager can use page sizes ranging from:
a. 4 KB to 64 KB
Fill-In-The-Blank Questions:
31. In a system employing a memory management strategy that doesnt require an
entire process to be in main memory at one time, the portion of a process that is
actually in main memory at any given time is defined to be the resident set of the
process.
32. The situation where the processor spends most of its time swapping process
pieces rather than executing instructions is called thrashing.
33. Most virtual memory schemes make use of a special high-speed cache for page
table entries, called a translation lookaside buffer (TLB).
34. Each entry in a page table contains control bits and the corresponding frame
number if the page is resident in memory.
35. In a segmentation system, each entry in a segment table contains control bits
and the starting address and the length of the segment.
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36. Paging, which is transparent to the programmer, eliminates external
fragmentation, provides efficient use of main memory, and has pieces of fixed,
equal size.
37. Segmentation, which is visible to the programmer, has the ability to handle
growing data structures, modularity, and support for sharing and protection.
38. An example of an O/S that doesnt provide virtual memory is MS-DOS or early
UNIX.
39. The fetch policy where a page is brought into main memory only if a reference is
made to a location on that page is called demand paging.
40. The replacement policy that treats the page frames allocated to a process as a
circular buffer is called FIFO.
41. A local replacement policy chooses only among the resident ages of the process
that generated the page fault in selecting a page to replace.
Operating Systems, 6th ed.
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3. T / F Medium-term scheduling is part of the system swapping function.
4. T / F The long-term scheduler is invoked whenever an event occurs that may
lead to the suspension or preemption of the currently running process.
5. T / F The main objective of short-term scheduling is to allocate processor time
in such a way as to optimize one or more aspects of system behavior.
6. T / F One problem with a pure priority scheduling scheme is that lower-priority
processes may suffer deadlock.
7. T / F The selection function determines which process, among ready
processes, is selected next for execution.
8. T / F First-come-first-served (FCFS) is a simple scheduling policy that tends to
favor I/O-bound processes over processor bound processes.
9. T / F Round Robin is a scheduling technique is also known as time slicing,
because each process is given a slice of time before being preempted.
42. A precleaning policy writes modified pages before their page frames are needed
so that pages can be written out in batches.
10. T / F The Shortest Process Next (SPN) scheduling policy is often used for timesharing and transaction processing environments because of the lack of
preemption.
43. In SVR4 and Solaris systems, the memory management scheme that manages
memory allocation for the kernel is called the kernel memory allocato..
11. T / F The Shortest Remaining Time (SRT) scheduling policy is a preemptive
version of the Shortest Process Next (SPN) scheduling policy.
44. Linux systems use a three level page table structure in its memory management
scheme to accommodate large addresses.
12. T / F In the Highest Response Ratio Next (HRRN) scheduling policy, longer
jobs are favored, because they yield a larger ratio from the smaller denominator
in the equation.
45. In a W2K system, although each user sees a 32-bit address space, allowing 4
GB of memory per process, a portion of this memory is reserved for O/S use, so
a user process actually has access to 2 GB of virtual address space.
Chapter 9 Uniprocessor Scheduling
13. T / F A disadvantage of simulation is that results for a given run only apply to
that particular collection of processes under that particular set of assumptions.
14. T / F In fair share scheduling, each user is assigned a weighting of some sort
that defines that users share of system resources as a fraction of the total usage
of those resources.
15. T / F The traditional UNIX scheduler, such as those used in SVR3 and 4.3 BSD
UNIX systems, employs single level feedback using round robin.
True / False Questions:
1. T / F Scheduling affects the performance of a system because it determines
which processes will wait and which will progress.
Multiple Choice Questions:
2. T / F The short-term scheduler may limit the degree of multiprogramming to
provide satisfactory service to the current set of processes.
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46. The type of scheduling that involves the decision to add a process to those that
are at least partially in main memory and therefore available for execution is
referred to as:
a. Long-term scheduling
c. I/O scheduling
b. Medium-term scheduling
d. None of the above
47. The decision as to which job to admit to the system next can be based on which
of the following criteria:
a. Simple FIFO
c. I/O requirements
b. Priority
d. All of the above
48. Typically, the swapping-in function for processes is based on the need to
manage:
a. Process priorities
c. The degree of
b. Virtual memory
multiprogramming
d. None of the above
49. In terms of frequency of execution, the short-term scheduler is usually the one
that executes:
a. Most frequently
c. About the same as the
b. Least frequently
other schedulers
d. None of the above
50. Response time in an interactive system is an example of:
a. System-oriented criteria for short-term scheduling policies
b. User-oriented criteria for short-term scheduling policies
c. System-oriented criteria for long-term scheduling policies
d. None of the above
51. A typical way to overcome starvation of lower-priority processes in a prioritybased scheduling system is to:
c. Round-robin cycling of
a. Change a process priority
processes in a priority
randomly
queue
b. Change a process priority
d. All of the above
with its age
52. Which of the following scheduling policies allow the O/S to interrupt the currently
running process and move it to the Ready state?
a. Preemptive
c. First-come-first-served
b. Non-Preemptive
d. None of the above
53. In terms of the queuing model, the total time that a process spends in a system
(waiting time plus service time) is called:
a. Normalized turnaround
c. Turnaround or residence
time (TAT)
time (TAT)
b. Finish time (FT)
d. None of the above
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54. In the Round Robin scheduling technique, the principle design issue is:
a. Determining the fair distribution of time quanta to individual processes
b. Determining the method of cycling through a given set of processes
c. Determining the length of the time quantum
d. None of the above
55. One difficulty with the Shortest Process Next (SPN) scheduling technique is:
a.
b.
c.
d.
The need to know or estimate required processing times for each process
The starvation of longer processes
The lack of preemption
All of the above
56. One difficulty with the Shortest Remaining Time (SRT) scheduling technique is:
a. The need to know or estimate required processing times for each process
b. The starvation of shorter processes
c. The lack of preemption
d. All of the above
57. Which of the following scheduling policies require prior knowledge or estimation
of process length:
a. Shortest Remaining Time (SRT)
b. Shortest Process Next (SPN)
c. Highest Response Ratio Next (HRRN)
d. All of the above
58. It is impossible to make definitive comparisons of various scheduling policies due
to dependence on factors such as:
a. The probability distribution of service times of the various processes
b. The efficiency of the scheduling and context switching mechanisms
c. The nature of the I/O demand and performance of the I/O subsystem
d. All of the above
59. The strategy that schedules processes based on their group affiliation is
generally referred to as:
a. Queuing analysis
c. Fair share scheduling
b. Simulation modeling
d. All of the above
60. The traditional UNIX scheduler divides processes into fixed bands of priority
levels, with the highest priority band being the:
a. Swapper band
c. User process band
b. File manipulation band
d. None of the above
Fill-In-The-Blank Questions:
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61. The task of assigning processes to the processor or processors over time, in a
way that meets system objectives is called scheduling.
62. The decision as to when to create a new process is generally driven by the
desired degree of multiprogramming.
63. Medium term scheduling is part of the system swapping function.
64. The short term scheduler is invoked whenever an event occurs that may lead to
the suspension or preemption of the currently running process.
65. Response time and throughput are examples of performance-related criteria for
short-term scheduling
66. In a system employing priority scheduling, the scheduler always selects the
process with the highest priority level for processing.
67. The decision mode which has two general categories, specifies the instants in
time at which the selection function is exercised.
68. In terms of the queuing model, the total time that a process spends in a system
(waiting time plus service time) is called the turnaround time (TAT).
69. The Round Robin scheduling technique is also known as time slicing, because
each process is given a set amount of processor time before being preempted.
70. Shortest process next (SPN) is a scheduling policy in which the process with the
shortest expected processing time is selected next, but there is no preemption.
71. Shortest remaining time (SRT) is a scheduling policy in which the process with
the shortest expected processing time is selected next, and if a shorter process
becomes ready in the system, the currently running process is preempted.
72. A scheduling mechanism that requires no prior knowledge of process length, yet
can nevertheless favor shorter jobs, is known as the feedback scheduling
mechanism.
73. Some of the difficulties of analytic modeling are overcome by using discreteevent simulation, which allows a wide range of policies to be modeled.
74. In fair share scheduling, each user is assigned a weighting of some sort that
defines that users share of system resources as a fraction of the total usage of
those resources.
75. The traditional UNIX scheduler, such as those used in SVR3 and 4.3 BSD UNIX
systems, divides processes into fixed bands of priority levels.
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