logging in or signing up cpu sheduling sawanprasad Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 563 Category: Science & Tech.. License: All Rights Reserved Like it (0) Dislike it (0) Added: September 04, 2010 This Presentation is Public Favorites: 0 Presentation Description Basic Concepts Scheduling Criteria Scheduling Algorithms Comments Posting comment... By: delmo22 (15 month(s) ago) Hi Dear sawanprasad, This is a good presentation... Please can you allow us to download it or f you don't mind to email t to me at delomongoto@yahoo.co.uk Many thanks Delo Saving..... Post Reply Close Saving..... Edit Comment Close By: piyushkhandelwal993 (15 month(s) ago) Nice presentation................................ Saving..... Post Reply Close Saving..... Edit Comment Close Premium member Presentation Transcript CPU Scheduling : CPU Scheduling Prof.Prasad Sawant Lecturer MCA MACS College Pune Operating System Concepts Prasad Sawant Alternating Sequence of CPU And I/O Bursts : Alternating Sequence of CPU And I/O Bursts Operating System Concepts Prasad Sawant CPU Scheduler : CPU Scheduler Selects from among the processes in memory that are ready to execute, and allocates the CPU to one of them. CPU scheduling decisions may take place when a process: 1. Switches from running to waiting state. 2. Switches from running to ready state. 3. Switches from waiting to ready. 4. Terminates. Scheduling under 1 and 4 is nonpreemptive. All other scheduling is preemptive. Operating System Concepts Prasad Sawant Dispatcher : Dispatcher Dispatcher module gives control of the CPU to the process selected by the short-term scheduler. Operating System Concepts Prasad Sawant Scheduling Criteria : Scheduling Criteria 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 Operating System Concepts Prasad Sawant Keep in mind : Keep in mind Waiting time (WT)=start time(ST)-Arrival time (AT) Finish time (FT)=start time(ST)+Burst Time(BT) Total turn around time(TOT)=Finish time(FT)-Arrival time (AT ) Operating System Concepts Prasad Sawant Optimization Criteria : Optimization Criteria Max CPU utilization Max throughput Min turnaround time Min waiting time Min response time Operating System Concepts Prasad Sawant First-Come, First-Served (FCFS) Scheduling : First-Come, First-Served (FCFS) Scheduling Operating System Concepts Prasad Sawant Suppose that the processes arrive in the order: P1 , P2 , P3 0 10 20 30 P1 24 P2 27 P3 30 Waiting time for P1 = 0; P2 = 24; P3 = 27 Average waiting time: (0 + 24 + 27)/3 = 17 schedule schedule schedule First-Come, First-Served (FCFS) Scheduling Gantt Chart : First-Come, First-Served (FCFS) Scheduling Gantt Chart Operating System Concepts Prasad Sawant Suppose that the processes arrive in the order: P1 , P2 , P3 Waiting time for P1 = 0; P2 = 24; P3 = 27 Average waiting time: (0 + 24 + 27)/3 = 17 schedule schedule schedule 0 P1 24 P2 27 P3 30 Exercise : Exercise Find Average waiting time for Suppose that the processes arrive in the order: P2 , P3 , P1 Operating System Concepts Prasad Sawant Shortest-Job-First (SJR) Scheduling : Shortest-Job-First (SJR) Scheduling Associate with each process the length of its next CPU burst. Use these lengths to schedule the process with the shortest time. Two schemes: nonpreemptive – once CPU given to the process it cannot be preempted until completes its CPU burst. preemptive – 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). SJF is optimal – gives minimum average waiting time for a given set of processes. Operating System Concepts Prasad Sawant Example of Non-Preemptive SJF : Example of Non-Preemptive SJF Operating System Concepts Prasad Sawant 0 P1 7 P3 8 P2 12 P4 16 schedule schedule schedule schedule Average waiting time = (0+6+3+7)/4=4 Example of Non-Preemptive SJF : Example of Non-Preemptive SJF Operating System Concepts Prasad Sawant P1 7 P3 8 P2 12 P4 16 Average waiting time = (0+6+3+7)/4=4 Average TOT =(7+10+4+11)/4=8 Preemptive SJF : Preemptive SJF Operating System Concepts Prasad Sawant 0 P1 1 P2 5 P schedule P4 10 schedule 7 P1 17 schedule P3 26 schedule 10 1 17 5 10-1=9 1-1=0 17-2=15 5-3=2 Priority Scheduling : Priority Scheduling Operating System Concepts Prasad Sawant 0 P2 1 0 P5 6 P1 16 P3 18 P4 19 Schedule Schedule Schedule Schedule Schedule 6 0 16 18 1 6 0 16 18 1 41/5=8.2 ms SJF Preemptive Priority Scheduling : SJF Preemptive Priority Scheduling Operating System Concepts Prasad Sawant 0 P1 3 P 5 P4 12 scheduled P3 19 scheduled P1 24 scheduled P2 30 scheduled 19 24 12 3 19-3=16 24-1=23 12-3=9 3-3=0 48/4=12 ms Round Robin Scheduling : Round Robin Scheduling 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 there are n processes in 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 units at once. No process waits more than (n-1)q time units. Operating System Concepts Prasad Sawant Time Quantum and Context Switch Time : Time Quantum and Context Switch Time Operating System Concepts Prasad Sawant 0 1 9 0 10 6 10 2 3 4 5 6 7 8 9 10 1 Round Robin Time Quantum 4 : Round Robin Time Quantum 4 Operating System Concepts Prasad Sawant 0 P1 4 24-4=20 P2 7 scheduled P3 10 scheduled P1 14 20-4=16 P1 18 16-4=12 P1 22 12-4=8 P1 26 8-4=4 P1 30 4-4=0 scheduled 30 7 10 Questions : Questions Define the difference between pre-emptive and non-pre-emptive scheduling. Explain the concept of a priority used in scheduling. Why is priority working usually chosen for real time processes? Define by difference between preemptive and non-emptive scheduling. Comment on the principle disadvantage of each of these scheduling methods: FCFS, SJF, RR Operating System Concepts Prasad Sawant Bibliography : Bibliography Operating System Principle-Peter Galvin Galvin Prof.S.G.Lakhdive (Dept .Computer Sci ) Prof.Ramkirshna More A.C.S College Akurdi Mr. Abhishek Nagar Web Administrator at Symbiois Operating System Concepts Prasad Sawant Slide 22: Thanks you Operating System Concepts Prasad Sawant You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.
cpu sheduling sawanprasad Download Post to : URL : Related Presentations : Share Add to Flag Embed Email Send to Blogs and Networks Add to Channel Uploaded from authorPOINT lite Insert YouTube videos in PowerPont slides with aS Desktop Copy embed code: (To copy code, click on the text box) Embed: URL: Thumbnail: WordPress Embed Customize Embed The presentation is successfully added In Your Favorites. Views: 563 Category: Science & Tech.. License: All Rights Reserved Like it (0) Dislike it (0) Added: September 04, 2010 This Presentation is Public Favorites: 0 Presentation Description Basic Concepts Scheduling Criteria Scheduling Algorithms Comments Posting comment... By: delmo22 (15 month(s) ago) Hi Dear sawanprasad, This is a good presentation... Please can you allow us to download it or f you don't mind to email t to me at delomongoto@yahoo.co.uk Many thanks Delo Saving..... Post Reply Close Saving..... Edit Comment Close By: piyushkhandelwal993 (15 month(s) ago) Nice presentation................................ Saving..... Post Reply Close Saving..... Edit Comment Close Premium member Presentation Transcript CPU Scheduling : CPU Scheduling Prof.Prasad Sawant Lecturer MCA MACS College Pune Operating System Concepts Prasad Sawant Alternating Sequence of CPU And I/O Bursts : Alternating Sequence of CPU And I/O Bursts Operating System Concepts Prasad Sawant CPU Scheduler : CPU Scheduler Selects from among the processes in memory that are ready to execute, and allocates the CPU to one of them. CPU scheduling decisions may take place when a process: 1. Switches from running to waiting state. 2. Switches from running to ready state. 3. Switches from waiting to ready. 4. Terminates. Scheduling under 1 and 4 is nonpreemptive. All other scheduling is preemptive. Operating System Concepts Prasad Sawant Dispatcher : Dispatcher Dispatcher module gives control of the CPU to the process selected by the short-term scheduler. Operating System Concepts Prasad Sawant Scheduling Criteria : Scheduling Criteria 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 Operating System Concepts Prasad Sawant Keep in mind : Keep in mind Waiting time (WT)=start time(ST)-Arrival time (AT) Finish time (FT)=start time(ST)+Burst Time(BT) Total turn around time(TOT)=Finish time(FT)-Arrival time (AT ) Operating System Concepts Prasad Sawant Optimization Criteria : Optimization Criteria Max CPU utilization Max throughput Min turnaround time Min waiting time Min response time Operating System Concepts Prasad Sawant First-Come, First-Served (FCFS) Scheduling : First-Come, First-Served (FCFS) Scheduling Operating System Concepts Prasad Sawant Suppose that the processes arrive in the order: P1 , P2 , P3 0 10 20 30 P1 24 P2 27 P3 30 Waiting time for P1 = 0; P2 = 24; P3 = 27 Average waiting time: (0 + 24 + 27)/3 = 17 schedule schedule schedule First-Come, First-Served (FCFS) Scheduling Gantt Chart : First-Come, First-Served (FCFS) Scheduling Gantt Chart Operating System Concepts Prasad Sawant Suppose that the processes arrive in the order: P1 , P2 , P3 Waiting time for P1 = 0; P2 = 24; P3 = 27 Average waiting time: (0 + 24 + 27)/3 = 17 schedule schedule schedule 0 P1 24 P2 27 P3 30 Exercise : Exercise Find Average waiting time for Suppose that the processes arrive in the order: P2 , P3 , P1 Operating System Concepts Prasad Sawant Shortest-Job-First (SJR) Scheduling : Shortest-Job-First (SJR) Scheduling Associate with each process the length of its next CPU burst. Use these lengths to schedule the process with the shortest time. Two schemes: nonpreemptive – once CPU given to the process it cannot be preempted until completes its CPU burst. preemptive – 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). SJF is optimal – gives minimum average waiting time for a given set of processes. Operating System Concepts Prasad Sawant Example of Non-Preemptive SJF : Example of Non-Preemptive SJF Operating System Concepts Prasad Sawant 0 P1 7 P3 8 P2 12 P4 16 schedule schedule schedule schedule Average waiting time = (0+6+3+7)/4=4 Example of Non-Preemptive SJF : Example of Non-Preemptive SJF Operating System Concepts Prasad Sawant P1 7 P3 8 P2 12 P4 16 Average waiting time = (0+6+3+7)/4=4 Average TOT =(7+10+4+11)/4=8 Preemptive SJF : Preemptive SJF Operating System Concepts Prasad Sawant 0 P1 1 P2 5 P schedule P4 10 schedule 7 P1 17 schedule P3 26 schedule 10 1 17 5 10-1=9 1-1=0 17-2=15 5-3=2 Priority Scheduling : Priority Scheduling Operating System Concepts Prasad Sawant 0 P2 1 0 P5 6 P1 16 P3 18 P4 19 Schedule Schedule Schedule Schedule Schedule 6 0 16 18 1 6 0 16 18 1 41/5=8.2 ms SJF Preemptive Priority Scheduling : SJF Preemptive Priority Scheduling Operating System Concepts Prasad Sawant 0 P1 3 P 5 P4 12 scheduled P3 19 scheduled P1 24 scheduled P2 30 scheduled 19 24 12 3 19-3=16 24-1=23 12-3=9 3-3=0 48/4=12 ms Round Robin Scheduling : Round Robin Scheduling 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 there are n processes in 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 units at once. No process waits more than (n-1)q time units. Operating System Concepts Prasad Sawant Time Quantum and Context Switch Time : Time Quantum and Context Switch Time Operating System Concepts Prasad Sawant 0 1 9 0 10 6 10 2 3 4 5 6 7 8 9 10 1 Round Robin Time Quantum 4 : Round Robin Time Quantum 4 Operating System Concepts Prasad Sawant 0 P1 4 24-4=20 P2 7 scheduled P3 10 scheduled P1 14 20-4=16 P1 18 16-4=12 P1 22 12-4=8 P1 26 8-4=4 P1 30 4-4=0 scheduled 30 7 10 Questions : Questions Define the difference between pre-emptive and non-pre-emptive scheduling. Explain the concept of a priority used in scheduling. Why is priority working usually chosen for real time processes? Define by difference between preemptive and non-emptive scheduling. Comment on the principle disadvantage of each of these scheduling methods: FCFS, SJF, RR Operating System Concepts Prasad Sawant Bibliography : Bibliography Operating System Principle-Peter Galvin Galvin Prof.S.G.Lakhdive (Dept .Computer Sci ) Prof.Ramkirshna More A.C.S College Akurdi Mr. Abhishek Nagar Web Administrator at Symbiois Operating System Concepts Prasad Sawant Slide 22: Thanks you Operating System Concepts Prasad Sawant