Chap 9 Flashcards
In a multiprogramming system multiple processes exist concurrently in main memory.
TRUE
The key to multiprogramming is scheduling.
TRUE
The medium-term scheduler is invoked whenever an event occurs that may lead to the blocking of the current process or that may provide an opportunity to preempt a currently running process in favor of another.
FALSE
Scheduling affects the performance of the system because it determines which processes will wait and which will progress.
TRUE
The main objective of long-term scheduling is to allocate processor time in such a way as to optimize one or more aspects of system behavior
FALSE
In most interactive operating systems adequate response time is the critical requirement.
TRUE
One problem with a pure priority scheduling scheme is that lower-priority processes may suffer starvation.
TRUE
First-come-first-serve (FCFS) performs much better for short processes than long ones.
FALSE
Round robin is particularly effective in a general-purpose time-sharing system or transaction processing system.
TRUE
The objective of a fair-share scheduler is to monitor usage to give fewer resources to users who have had more than their fair share, and more to those who have had less than their fair share.
TRUE
The traditional UNIX scheduler employs multilevel feedback user round robin within each of the priority queues.
TRUE
First-come-first-serve (FCFS) is a simple scheduling policy that tends to favor I/O-bound processes over processor-bound processes.
FALSE
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.
FALSE
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.
TRUE
In fair share scheduling each user is assigned a weighting of some sort that defines that user’s share of system resources as a fraction of the total usage of those resources.
TRUE
The decision as to which available process will be executed by the processor: _______________
short term scheduling
The __________ determines which process, among ready processes, is selected next for execution.
selection function
Which scheduling policy allows the OS to interrupt the currently running process and move it to the Ready state?
preemptive
The __________ specifies the instants in time at which the selection function is exercised.
decision mode
The traditional UNIX scheduler divides processes into fixed bands of priority levels, with the highest priority band being the _________.
swapper band
This is a decision whether to add a new process to the set of processes that are currently active:
long term scheduling
A risk with __________ is the possibility of starvation for longer processes, as long as there is a steady supply of shorter processes.
SPN
The decision as to which process’ pending I/O request shall be handled by an available I/O device:
I/O scheduling
In the case of the _________ policy, the scheduler always chooses the process that has the shortest expected remaining processing time.
SRT (Shortest Remaining Time)
This is a decision on whether to add a process to those that are at least partially in the main memory and therefore available for execution.
medium-term scheduling
Response time in an interactive system is an example of:
user-oriented criteria for short-term policies
__________ considers the execution history of a related group of processes along with the individual execution history of each process in making scheduling decisions.
FSS
The operating system must make ________ types of scheduling decisions with respect to the execution of processes.
3
Typically, the swapping-in function for processes is based on the need to manage ___________.
degree of multiprogramming
The strategy that schedules processes based on their group affiliation is generally referred to as ___________.
fair share scheduling
The aim of ________ is to assign processes to be executed by the processor or processors over time, in a way that meets system objectives, such as response time, throughput, and processor efficiency.
processor scheduling
The __________ scheduler determines which programs are admitted to the system for processing.
long term
_________ is the elapsed time between the submission of a request until the response begins to appear as output.
response time
The simplest scheduling policy is __________.
first come first served
__________ scheduling is part of the swapping function.
medium term
In terms of the queuing model, _________ is the total time that the item spends in the system (waiting time plus service time).
turnaround time
Giving each process a slice of time before being preempted is a technique known as __________.
time slicing
A common technique for predicting a future value on the basis of a time series of past values is __________.
exponential averaging
The ___________ scheduler executes most frequently and makes the fine-grained decision of which process to execute next.
short term
The _________ approach means that the operating system allocates the processor to a process and when the process blocks or is preempted, feeds it back into one of several priority queues.
multilevel feedback
The need to know or estimate required processing times for each process, the starvation of longer processes, and the lack of preemption are all difficulties with the __________ scheduling technique.
Shortest Process Next (SPN)
Response time and throughput are examples of __________ criteria for short-term scheduling.
performance-based
_________ is a scheduling policy in which the process with the shortest expected processing time is select next, and if a shorter process becomes ready in the system, the currently running process is preempted.
Shortest Remaining Time (SRT)
The traditional UNIX scheduler, such as those used in SVR3 and 4.3 BSD UNIX systems, divides processes into fixed ________ of priority levels.
bands
A scheduling mechanism that requires no prior knowledge of process length yet can nevertheless favor shorter jobs, is known as the _________ scheduling mechanism.
feedback
