Memory Management

Question 1

Which of the following is a benefit of allowing a program that is only partially in memory to
execute?
A) Programs can be written to use more memory than is available in physical memory.
B) CPU utilization and throughput is increased.
C) Less I/O is needed to load or swap each user program into memory.
D) All of the above

Answer 1

D- ALL OF THE ABOVE

Question 2

In systems that support virtual memory, ____.
A) virtual memory is separated from logical memory.
B) virtual memory is separated from physical memory.
C) physical memory is separated from secondary storage.
D) physical memory is separated from logical memory

Answer 2

D- PHYSICAL MEMORY IS SEPARATED FROM LOGICAL MEMORY

Question 3

The vfork() system call in UNIX ____.
A) allows the child process to use the address space of the parent
B) uses copy-on-write with the fork() call
C) is not intended to be used when the child process calls exec() immediately after creation
D) duplicates all pages that are modified by the child process

Answer 3

A- ALLOWS THE CHILD PROCESS TO USE THE ADDRESS SPACE OF THE PARENT

Question 4

Belady’s anomaly states that ____.
A) giving more memory to a process will improve its performance
B) as the number of allocated frames increases, the page-fault rate may decrease for all page
replacement algorithms
C) for some page replacement algorithms, the page-fault rate may decrease as the number of
allocated frames increases
D) for some page replacement algorithms, the page-fault rate may increase as the number of
allocated frames increases

Answer 4

D- FOR SOME PAGE REPLACEMENT ALGORITHMS, THE PAGE-FAULT RATE MAY INCREASE AS THE NUMBER OF ALLOCATED FRAMES INCREASES

Question 5

Optimal page replacement ____.
A) is the page-replacement algorithm most often implemented
B) is used mostly for comparison with other page-replacement schemes
C) can suffer from Belady’s anomaly
D) requires that the system keep track of previously used pages

Answer 5

B- IS USED MOSTLY FOR COMPARISON WITH OTHER PAGE-REPLACEMENT SCHEMES

Question 6

The _____ allocation algorithm allocates available memory to each process according to its size.
A) equal
B) global
C) proportional
D) slab

Answer 6

C- PROPORTIONAL

Question 7

The \_\_\_\_ is the number of entries in the TLB multiplied by the page size.
A) TLB cache
B) page resolution
C) TLB reach
D) hit ratio

Answer 7

C- TLB REACH

Question 8

________ allows the parent and child processes to initially share the same pages, but when either process modifies a page, a copy of the shared page is created.
A) copy-on-write
B) zero-fill-on-demand
C) memory-mapped
D) virtual memory fork

Answer 8

A- COPY-ON-WRITE

Question 9

_____ is the algorithm implemented on most systems. (for page fault)
A) FIFO
B) Least frequently used
C) Most frequently used
D) LRU
~~~

Answer 9

D- LRU

LRU stands for Least Recently Used. As the name suggests, this algorithm is based on the strategy that whenever a page fault occurs, the least recently used page will be replaced with a new page

Question 10

. \_\_\_\_\_ occurs when a process spends more time paging than executing.
A) Thrashing
B) Memory-mapping
C) Demand paging
D) Swapping

Answer 10

A- THRASHING

Question 11

Windows uses a local page replacement policy _____.
A) when a process exceeds its working set minimum
B) when a process exceeds its working set maximum
C) when the system undergoes automatic working set trimming
D) under all circumstances

Answer 11

B- WHEN A PROCESS EXCEEDS ITS WORKING SET MAXIMUM

Explanation for C:
When a system undergoes automatic working set trimming, it means that the operating system or a memory management component dynamically adjusts the working set of a process to optimize memory usage and system performance.

The working set of a process refers to the subset of its pages that are actively used to access during a specific time period. It represents the set of pages that the process requires to execute efficiently without incurring excessive page faults.

Question 12

Which of the following statements is false with regard to Solaris memory management?
A) The speed at which pages are examined (the scanrate) is constant.
B) The pageout process only runs if the number of free pages is less than lotsfree.
C) An LRU approximation algorithm is employed.
D) Pages selected for replacement may be reclaimed before being placed on the free list.

Answer 12

A- THE SPEED AT WHICH PAGES ARE EXAMINED (THE SCANRATE) IS CONSTANT

Question 13

Which of the following statements is false with regard to allocating kernel memory?
A) Slab allocation does not suffer from fragmentation.
B) Adjacent segments can be combined into one larger segment with the buddy system.
C) Because the kernel requests memory of varying sizes, some of which may be quite small, the system does not have to be concerned about wasting memory

Answer 13

C

Question 14

The _____ is an approximation of a program’s locality.
A) locality model
B) working set
C) page fault frequency
D) page replacement algorithm

Answer 14

B- WORKING SET

Working set: set of actively used resources or data elements in a program or system at a given point in time.

Program locality refers to the tendency of a program to access certain data or instructions more frequently or in a clustered manner

Question 15

\_\_\_\_\_\_ allows a portion of a virtual address space to be logically associated with a file.
A) Memory-mapping
B) Shared memory
C) Slab allocation
D) Locality of reference

Answer 15

A- MEMORY MAPPING

Question 16

Systems in which memory access times vary significantly are known as \_\_\_\_\_\_\_\_\_\_.
A) memory-mapped I/O
B) demand-paged memory
C) non-uniform memory access
D) copy-on-write memory

Answer 16

C- NON-UNIFORM MEMORY ACCESS

Question 17

Which of the following is considered a benefit when using the slab allocator?
A) Memory is allocated using a simple power-of-2 allocator.
B) It allows kernel code and data to be efficiently paged.
C) It allows larger segments to be combined using coalescing.
D) There is no memory fragmentation.

Answer 17

D- THERE IS NO MEMORY FRAGMENTATION

Slab allocation is a memory management technique that offers benefits such as reduced fragmentation, improved memory locality, faster allocation and deallocation, efficient object management, caching, and scalability. It achieves these advantages by allocating memory in fixed-size slabs, allowing for efficient reuse and caching of memory blocks. Slab allocation is commonly used in operating systems and resource-intensive applications for efficient memory management.

Question 18

Systems in which memory access times vary significantly are known as __________.

Select one:

a. memory-mapped I/O
b. demand-paged memory
c. non-uniform memory access
d. copy-on-write memory

Answer 18

C- NON UNIFORM MEMORY ACCESS

Question 19

An address generated by a CPU is referred to as a ____.

Select one:

a. physical address
b. logical address
c. post relocation register address
d. memory management unit (MMU) generated address

Answer 19

B- LOGICAL ADDRESS

The MMU translates virtual addresses generated by the CPU into physical addresses. Virtual memory allows processes to use more memory than is physically available by utilizing secondary storage (e.g., hard disk) as an extension of the main memory.

Question 20

_____ is the dynamic storage allocation algorithm that results in the smallest leftover hole in memory.

Select one:

a. First-fit
b. Best-fit
c. Worst-fit
d. None of the above

Answer 20

B- BEST FIT

Question 21

_____ is the method of binding instructions and data to memory performed by most general-purpose operating systems.

Select one:

a. Interrupt binding
b. Compile time binding
c. Execution time binding
d. Load time binding

Answer 21

C- EXECUTION TIME BINDING

Execution time binding, also known as dynamic binding or late binding, refers to the process of determining the actual implementation or address of a function or method at runtime rather than at compile-time. It allows for the resolution of function calls or method invocations to be deferred until the program is executing.

Compared to compile-time binding or static binding, where the binding between function calls and implementations is determined during the compilation phase, execution time binding provides more flexibility and extensibility at the cost of some performance overhead due to the dynamic dispatch process.

The dynamic dispatch process, also known as dynamic method dispatch or runtime polymorphism, refers to the mechanism by which the appropriate implementation of a polymorphic method is determined and executed at runtime based on the actual type of the object being referenced.

Virtual Function Table (vtable): In languages like C++ and Java, a virtual function table, also known as a vtable, is used to store the addresses of the overridden methods for each class in the hierarchy. Each object of a class with virtual methods contains a hidden pointer to its corresponding vtable.

Question 22

_____ is the dynamic storage allocation algorithm that results in the largest leftover hole in memory.

Select one:

a. First-fit
b. Best-fit
c. Worst-fit
d. None of the above

Answer 22

C- WORST FIT

Question 23

Optimal page replacement ____.

Select one:

a. is the page replacement algorithm most often implemented
b. is used mostly for comparison with other page replacement schemes
c. can suffer from Belady’s anomaly
d. requires that the system keep track of previously used pages

Answer 23

B- IS USED MOSTLY FOR COMPARISON WITH OTHER PAGE REPLACEMENT SCHEMES

Optimal page replacement, also known as the OPT algorithm or clairvoyant algorithm, is an idealized page replacement algorithm that selects the page for eviction based on future knowledge of memory references. It assumes perfect knowledge of which pages will be accessed in the future and selects the page that will be used farthest in the future for replacement. Optimal page replacement provides the lowest possible number of page faults but is impractical to implement in real systems because it requires knowledge of future memory references. It is often used as a benchmark for evaluating other page replacement algorithms.

Belady’s anomaly highlights that the behavior of page replacement algorithms is not always predictable and can be counterintuitive. It implies that simply increasing the number of page frames may not always lead to better performance in terms of reducing page faults.

Question 24

What size segment will be allocated for a 39 KB request on a system using the buddy system for kernel memory allocation?

Select one:

a. 39 KB
b. 42 KB
c. 64 KB
d. none of the above

Answer 24

C- 64 Kb

In the buddy system, memory is allocated in powers of 2.

Question 25

Which of the following data structures is appropriate for placing into its own segment?

Select one:

a. heap
b. kernel code and data
c. user code and data
d. all of the above

Answer 25

D- ALL OF THE ABOVE

1.	Memory Isolation: Placing a data structure in its own segment can provide memory isolation and separation from other parts of the system. This isolation can help prevent unauthorized access or modification by restricting access permissions to the segment. It enhances security and protects critical data or code from being compromised.
2.	Access Control: Allocating a data structure in a separate segment allows for more granular access control. Access permissions and protections can be defined specifically for that segment, allowing fine-grained control over who can read, write, or execute the data structure. This is particularly important for sensitive data or critical system code that requires strict access restrictions.
3.	Memory Protection: By placing a data structure in its own segment, memory protection mechanisms can be applied to that segment. This allows the system to detect and handle illegal memory accesses, such as buffer overflows or invalid memory operations. Memory protection helps ensure the stability and reliability of the system by preventing memory corruption caused by faulty code or malicious attacks.
4.	Performance Optimization: Allocating a data structure in its own segment can help optimize performance. For example, if the data structure requires fast and efficient access, it can be placed in a separate segment with specific memory attributes or caching settings that are optimized for its access patterns. This can result in improved cache utilization, reduced contention, and faster access times.

Question 26

Which of the following statements is true with respect to hashed page tables?

Select one:

a. They only work for sparse address spaces.
b. The virtual address is used to hash into the hash table.
c. They are a common approach for handling address spaces larger than 32 bits.
d. Hash table collisions do not occur because of the importance of paging.

Answer 26

C- THEY ARE A COMMON APPROACH FOR HANDLING ADDRESS SPACES LARGER THAN 32 BITS

A hashed page table is a data structure used in operating systems to efficiently map virtual addresses in a computer’s memory management system.

Question 27

The ____ is the number of entries in the TLB multiplied by the page size.

Select one:

a. TLB cache
b. page resolution
c. TLB reach
d. hit ratio

Answer 27

C- TLB REACH

(Translation Lookaside Buffer) reach, refers to the ability of the TLB to effectively translate virtual addresses to physical addresses in a computer’s memory hierarchy.

Question 28

A(n) ____ page table has one page entry for each real page (or frame) of memory.

Select one:

a. inverted
b. clustered
c. forward-mapped
d. virtual

Answer 28

A- INVERTED

Unlike a traditional page table, which is typically implemented as an array or hash table, an inverted page table flips the structure around by indexing the table entries based on physical memory frames rather than virtual memory pages.

Question 29

Belady’s anomaly states that ____.

Select one:

a. giving more memory to a process will improve its performance
b. as the number of allocated frames increases, the page fault rate may decrease for all page replacement algorithms
c. for some page replacement algorithms, the page fault rate may decrease as the number of allocated frames increases
d. for some page replacement algorithms, the page fault rate may increase as the number of allocated frames increases

Answer 29

D- FOR SOME PAGE REPLACEMENT ALGORITHMS, THE PAGE FAULT RATE MAY INCREASE AS THE NUMBER OF ALLOCATED FRAMES INCREASES

Question 30

With segmentation, a logical address consists of _____.

Select one:

a. segment number and offset
b. segment name and offset
c. segment number and page number
d. segment table and segment number

Answer 30

A- SEGMENT NUMBER AND OFFSET

1. Segment Number: It represents the identification number assigned to a particular segment within a segmented memory model. In a segmented memory model, memory is divided into fixed-size segments, and each segment is assigned a unique number. The segment number is used to access or reference a specific segment within the memory model.
2. Offset: It refers to the distance or displacement from the beginning of a segment to a specific location within that segment. The offset is typically expressed in bytes and indicates the position of a particular data or instruction within the segment. It helps determine the precise memory address of the desired location by combining the segment number and offset values.

Question 31

In systems that support virtual memory, ____.

Select one:

a. virtual memory is separated from logical memory
b. virtual memory is separated from physical memory
c. physical memory is separated from secondary storage
d. physical memory is separated from logical memory

Answer 31

D- PHYSICAL MEMORY IS SEPARATED FROM LOGICAL MEMORY

The logical address is used as a reference to access the physical address.

Logical memory refers to the abstract view of memory that a process has.

Virtual memory is a memory management technique that provides an illusion of a larger memory space than what is physically available.

Question 32

_____ occurs when a process spends more time paging than executing.

Select one:

a. Thrashing
b. Memory mapping
c. Demand paging
d. Swapping

Answer 32

A- THRASHING

When the virtual memory of a computer is rapidly exchanging data for data on hard disk, to the exclusion of most application-level processing

The OS is swapping things in and out (of RAM) as needed. When this swapping activity is occurring such that it is the major consumer of the CPU time, then you are effectively thrashing.