CSC 414 Problems Session III, Spring 2007
Notre Dame University–Louaize · Applied Operating Systems · 1 page · Dr. Khaldoun El-Khaldi
Stuck on a question? A tutor can walk you through it.
More CSC 414 files
Show the text of this problems
CPU scheduling
Consider the following two preemptive CPU scheduling algorithms: Shortest Service
Time Next (SSTN)SSTN is a preemptive version of SJF, and Shortest Remaining
Service Time Next (SRSTN). Which of SSTN and SRSTN does give the smaller average
waiting time? Why?
SRSTN gives the smaller average waiting time.
In figure 1, B can arrive at time t1 ; t2 , or t3. Both performs trivially same for t1 and t2.
Suppose B arrives at t3 while A is executing.
(SSTN) B preempts A, then A must wait for the period y.
(SRSTN) A continues to execute until completion and B waits for the period x.
Waiting time of other processes are same and since y > x, SRSTN is better.