Chapter 5: CPU scheduling

Question 1

CPU util, throughput, turnaround time, waiting time, response time

Answer 1

CPU utilization – keep the CPU as busy as possible
Throughput – # of processes that complete their execution per time unit
Turnaround time – amount of time to execute a particular process
Waiting time – amount of time a process has been waiting in the ready queue
Response time – amount of time it takes from when a request was submitted until the first response is produced, not output (for time-sharing environment)

Question 2

What is starvation and how do we fix it

Answer 2

Problem  Starvation – low priority processes may never execute

Solution  Aging – as time progresses increase the priority of the process

Question 3

Asymetric multiprocessing vs symmetric

Answer 3

Asymmetric multiprocessing – only one processor accesses the system data structures, alleviating the need for data sharing
Symmetric multiprocessing (SMP) – each processor is self-scheduling, all processes in common ready queue, or each has its own private queue of ready processes

Question 4

cpu util equation

Answer 4

1- (%io wait)^n = cpu util

Question 5

Advantage and disadvantage of FCFS

Answer 5

simplest scheduling algorithm, but it can cause short processes to wait for very long processes

Question 6

Advantage and disadvantage of SJF

Answer 6

providing the shortest average waiting time.
Implementing SJF scheduling is difficult, however, because predicting the length of the next CPU burst is difficult.

Question 7

What is a multilevel queue

Answer 7

Multilevel queue scheduling partitions processes into several separate
queues arranged by priority, and the scheduler executes the processes in
the highest-priority queue. Different scheduling algorithms may be used
in each queue.