CPU scheduing

Question 1

-process execution consists of a cycle of CPU execution and I/O wait.

Answer 1

CPU-I/O Burst Cycle

Question 2

-selects from among the processes in memory that are ready to execute, and allocates the CPU to one of them.
-decisions:
1) switches from running to waiting state
2) switches from running to ready state
3) switches frm waiting to ready
4) terminates

scheduling under 1 and 4 is nonpreemptive
all other scheduling is preemptive

Answer 2

CPU scheduler

Question 3

-this module gives control of the CPU to the process selected by the short-term scheduler; this involves:
-switching context
-switching to user mode
-jumping to the proper location in the user program to restart that program.

Answer 3

dispatcher

Question 4

-time it takes for the dispatcher to stop one process and start another running

Answer 4

dispatch latency

Question 5

(scheduling criteria)
-keep the CPU as busy as possible

Answer 5

CPU utilization

Question 6

(scheduling criteria)
-# of processes that complete their execution per time unit

Answer 6

throughput

Question 7

(scheduling criteria)
-amount of time to execute a particular process

Answer 7

turnaround time

Question 8

(scheduling criteria)
-amount of time a process has been waiting in the ready queue.

Answer 8

waiting time

Question 9

(scheduling criteria)
-amount of time it takes from when a request was submitted until the first response is produced, not output (for time-sharing environment)

Answer 9

response time

Question 10

max CPU utilization
max throughput
min turnaround time
min waiting time
min response time

Answer 10

optimization criteria

Question 11

-once CPU given to the process it cannot be preempted until complete its CPU burst.

Answer 11

nonpreemptive

Question 12

-if a new process arrives with CPU burst length less than remaining time of current executing process, preempt. This scheme is know as the shortest-remaining-time-first (SRTF)

Answer 12

preemptive

Question 13

-associate with each process the length of its nexxt CPU burst. Use these length to schedule the process with the shortest time.
-is optimal-gives minimum average waiting time for a given set of processes.

Answer 13

shortest-job-first (SJR) scheduling

Question 14

-a priority number (integer) is associated with each process.
-the CPU allocated to the process with the highest priority (smallest integer = highest priority).

Answer 14

priority scheduling

Question 15

the problem with priority scheduling
-low priority processes may never execute

Answer 15

starvation

Question 16

-the solution to starvation
-as time porgresses increase the priority of the process

Answer 16

aging

Question 17

-each process gets a small unit of CPU time (time quantum), usually 10-100 milliseconds. After this time has elapsed, the process is preempted and added to the end of the ready queue,
-if these are n processes n the ready queue and the time quantum is q, then each process gets 1/n of the CPU time in chunks of at most q time nits at ones. No process waits more than (n-1) q time units.

Answer 17

round robin