Most Likely

Question 1

Deadlock occurs when

Answer 1

every process in a set is waiting for an event that can only be caused by another process in the set

Question 2

Deadlock can occur only when the following four conditions are satisfied:

Answer 2

Mutual exclusion

Hold and wait

No preemption

Circular wait

Question 3

Mutual exclusion

Answer 3

only one process at a time can use a resource

Question 4

Hold and wait

Answer 4

a process holding at least one resource is waiting to acquire additional resources held by other processes

Question 5

No preemption

Answer 5

a resource can be released only voluntarily by the process holding it, after that process has completed its task

Question 6

Circular wait

Answer 6

here exists a set {P0, P1, …, Pn} of waiting processes such that P0 is waiting for a resource that is held by P1, P1 is waiting for a resource that is held by P2, …, Pn-1 is waiting for a resource that is held by Pn, and Pn is waiting for a resource that is held by P0.

Question 7

A directed edge from a process to a resource is

Answer 7

called a request edge in system resource-allocation graph

Question 8

The assignment edge is

Answer 8

a directed edge from a resource to a process.

Question 9

A cycle in a resource-allocation graph is

Answer 9

not a sufficient condition for deadlock in the case that each resource has more than one instance.

Question 10

A cycle in a resource-allocation graph is sufficient and necessary only

Answer 10

if each resource has only one instance.

Question 11

Most OS pretend that deadlock

Answer 11

will never happen and leave it up to the responsibility of application programmer.

Question 12

An unsafe state may lead to a

Answer 12

deadlocked state, but not necessary must lead to.

Question 13

contiguous memory allocation

Answer 13

each process is contained in a single section of memory that is contiguous to the section containing the next process

With contiguous memory allocation, all portions of a process must be loaded into sequential physical memory partitions.

Question 14

First fit

Answer 14

Allocate program to the first partition big enough to hold it

Question 15

Best-fit

Answer 15

The allocator places a process in the smallest block of unallocated memory in which it will fit.

has the least wasted space and the smallest partition fitting the requirements.

Question 16

worst-fit

Answer 16

Allocate program to the largest partition big enough to hold it

Allocate the largest hole. Again, we must search the entire list, unless it is sorted by size.

Question 17

External fragmentation

Answer 17

is the phenomenon that results in unused blocks of memory outside of existing partitions.

Question 18

All processes in a computer system share a

Answer 18

single inverted page table.

Question 19

Each entry in the inverted page table contains

Answer 19

a process id and page number

Question 20

Pure paging has

Answer 20

fixed page size, has internal fragmentation (so wasted memory is from internal fragmentation)

Question 21

effective memory-access time

Answer 21

Average time required to access memory based on the TLB Hit Ratio.

Question 22

translation look-aside buffer

Answer 22

Hardware cache of recently used page table entries. Smaller page size increases page count, resulting in larger page tables and smaller ____ hit ratio.

A small but fast-lookup hardware cache which stores page and frame numbers for memory access.

Question 23

The optimal page replacement policy is

Answer 23

impossible to implement because it would require the OS to have perfect knowledge of future events.

Question 24

A dead-lock free solution may still

Answer 24

have the problem of starvation.

Question 25

Global replacement for page replacement which can select the replacement page from any other process has the problem that

Answer 25

a certain process cannot control it page-fault rate.

Question 26

Local replacement only allows the system to

Answer 26

choose a replacement page from the pages belonging to the same process. Global replacement algorithm is more frequently used due to its efficiency in utilizing memory resources.

Question 27

Copy-on-Write allows

Answer 27

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

Question 28

Thrashing occurs when

Answer 28

a process spends more time paging than executing.