Chapter 9 (Uniprocessor Scheduling) Flashcards
What does the long-term scheduler do?
Decides when to admit a process into the ready queue
What does the medium-term scheduler do?
Decides when to swap processes in and out of memory
What does the short-term scheduler do?
Decides which ready process to execute next
What two decisions does the long-term scheduler make?
Whether to admit a new process to the system
Which process to admit
T/F Medium-term scheduling can further manage the degree of multi programming
T
What is short-term scheduling also known as?
Dispatcher
What is user-oriented criteria?
Things the user sees
What is system-oriented criteria?
System concerns
What are some user-oriented performance-related criteria?
Turnaround time
Response time
Deadlines
What is a user-oriented other criteria?
Predictability
What are some system-oriented performance related criteria?
Throughput
Processor utilization
What are some system-oriented other criteria?
Fairness
Enforcing priorities
Balancing resources
What is a solution to prevent starving lower priority processes?
Aging a lower priority to a higher priority until it can eventually run
What is the selection function?
Which process runs next
What is the decision mode?
When to run the selection function
What are two approaches for decision mode?
Non-preemptive
Preemptive
Which scheduling algorithms are preemptive?
Round Robin (at timeout)
Feedback (at timeout)
Shortest remaining time (at arrival)
Which scheduling algorithms are non-preemptive?
First come first serve
Shortest process next
Highest response ratio next
What are the selection functions for:
Feedback
SPN
HRRN
RR
SRT
FCFS
N/A
min(s)
max((w+s)/s)
constant
min(s-e)
max(w)
Which scheduling algorithms have the potential for starvation?
SPN
SRT
Feedback
What jobs does RR favor?
Processor bound
What is a virtual RR scheduler?
Separate queue for processes returning from I/O and favor them
Which scheduling algorithm accounts for the age of a process?
HRRN
T/F In HRRN, each time a process is picked to execute, the ratio must be computed again for all processes
T
T/F Multilevel feedback requires a time estimate
F
What is a variation of multilevel feedback?
Assign longer quanta to lower queues
What is the key to effective multiprogramming?
Scheduling
What is the goal of scheduling?
Execute processes in such a way as to meet the system objectives, such as response time, throughput, and processes efficiency
