Chapter 6: CPU Scheduling. Operating System Concepts 9 th Edition
|
|
- Shon McDaniel
- 6 years ago
- Views:
Transcription
1 Chapter 6: CPU Scheduling Silberschatz, Galvin and Gagne 2013
2 Chapter 6: CPU Scheduling Basic Concepts Scheduling Criteria Scheduling Algorithms Thread Scheduling Multiple-Processor Scheduling Real-Time CPU Scheduling Operating Systems Examples Algorithm Evaluation 6.2 Silberschatz, Galvin and Gagne 2013
3 Objectives To introduce CPU scheduling, which is the basis for multiprogrammed operating systems To describe various CPU-scheduling algorithms To discuss evaluation criteria for selecting a CPU-scheduling algorithm for a particular system To examine the scheduling algorithms of several operating systems 6.3 Silberschatz, Galvin and Gagne 2013
4 Review the life cycle of a process in a single-processor system. A process is executed until it must wait, typically for the completion of some I/O request. 6.4 Silberschatz, Galvin and Gagne 2013
5 Basic Concepts CPU I/O Burst Cycle Process execution consists of a cycle of CPU execution and I/O wait CPU burst followed by I/O burst Maximum CPU utilization obtained with multiprogramming CPU burst distribution is of main concern 6.5 Silberschatz, Galvin and Gagne 2013
6 Histogram of CPU-burst Times An I/O-bound program typically has many short CPU bursts. A CPU-bound program might have a few long CPU bursts. Examples of I/O-bound program and CPU-bound programs? 6.6 Silberschatz, Galvin and Gagne 2013
7 Review: Schedulers Short-term scheduler (or CPU scheduler) selects which process should be executed next and allocates CPU Sometimes the only scheduler in a system (every process is in memory, like in Windows OS) Short-term scheduler is invoked frequently (milliseconds) (must be fast) Long-term scheduler (or job scheduler) selects which processes should be brought into the ready queue Long-term scheduler is invoked infrequently (seconds, minutes) (may be slow) The long-term scheduler controls the degree of multiprogramming Processes can be described as either: I/O-bound process spends more time doing I/O than computations, many short CPU bursts CPU-bound process spends more time doing computations; very long CPU bursts Long-term scheduler strives for good process mix What happens if all selected processes are I/O bound? What happens if all selected processes are CPU bound? 6.7 Silberschatz, Galvin and Gagne 2013
8 Medium Term Scheduler Medium-term scheduler can be added if degree of multiple programming needs to decrease Remove process from memory, store on disk, bring back in from disk to continue execution: swapping Why medium-term scheduler? May be necessary to improve the process mix or to free memory 6.8 Silberschatz, Galvin and Gagne 2013
9 CPU Scheduler When can process scheduling take place? 6.9 Silberschatz, Galvin and Gagne 2013
10 CPU Scheduler (cont.) 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 only 1 and 4 is nonpreemptive or cooperative. Once the CPU has been allocated to a process, the process keeps the CPU until it releases the CPU either by terminating or by switching to the waiting state. Used by Microsoft Windows 3.x Windows 95 introduced preemptive scheduling, and all subsequent versions of Windows OS have used preemptive scheduling Silberschatz, Galvin and Gagne 2013
11 CPU Scheduler (cont.) Otherwise scheduling is preemptive Preemptive scheduling can result in race conditions when data are shared among several processes: Consider access to shared data the example given in Chapter 5. Preemption also affects the design of the operating-system kernel. Consider preemption while in kernel mode. Several OS, including most versions of UNIX, deal with this problem by waiting either for a system call to complete or for an I/O block to take place before doing a context switch. This kernel-execution model is a poor one for supporting real time computing. Consider interrupts occurring during crucial OS activities. The sections of code affected by interrupts must be guarded from simultaneous use. Disable interrupts at entry and reenable interrupts at exit. The sections of code that disable interrupts do not occur very often and typically contain few instructions Silberschatz, Galvin and Gagne 2013
12 Dispatcher Dispatcher 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 Dispatch latency time it takes for the dispatcher to stop one process and start another running 6.12 Silberschatz, Galvin and Gagne 2013
13 Scheduling Criteria What criteria make sense? 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 timesharing environment) For interactive systems (such as desktop systems), it is more important to minimize the variance in the response time than to minimize the average response time. However, little work has been done on CPU-scheduling algorithms that minimize variance Silberschatz, Galvin and Gagne 2013
14 Scheduling Algorithm Optimization Criteria CPU utilization throughput the number of processes that are completed per time unit turnaround time the sum of the periods spent waiting to get into memory, waiting in the ready queue, executing on the CPU, and doing I/O. waiting time the sum of the periods spent waiting in the ready queue. response time the time it takes to start responding, not the time it takes to output the response. For interactive systems (such as desktop systems), it is more important to minimize the variance in the response time than to minimize the average response time Silberschatz, Galvin and Gagne 2013
15 First- Come, First-Served (FCFS) Scheduling Process Burst Time P 1 24 P 2 3 P 3 3 Suppose that the processes arrive in the order: P 1, P 2, P 3 The Gantt Chart for the schedule is: P P P Waiting time for P 1 = 0; P 2 = 24; P 3 = 27 Average waiting time: ( )/3 = Silberschatz, Galvin and Gagne 2013
16 FCFS Scheduling (Cont.) Suppose that the processes arrive in the order: P 2, P 3, P 1 The Gantt chart for the schedule is: P 2 P 3 P Waiting time for P 1 = 6; P 2 = 0 ; P 3 = 3 Average waiting time: ( )/3 = 3 Much better than previous case Note that the FCFS scheduling algorithm is nonpreemptive. Convoy effect - short process behind long process Consider one CPU-bound and many I/O-bound processes as an example, what will happen using the FCFS scheduling? How to improve this? 6.16 Silberschatz, Galvin and Gagne 2013
17 Shortest-Job-First (SJF) Scheduling Associate with each process the length of its next CPU burst Use these lengths to schedule the process with the shortest time SJF is optimal gives minimum average waiting time for a given set of processes The difficulty is knowing the length of the next CPU request Could ask the user 6.17 Silberschatz, Galvin and Gagne 2013
18 Example of SJF ProcessArrival Time Burst Time P P P P SJF scheduling chart P 4 P 1 P 3 P Average waiting time = ( ) / 4 = Silberschatz, Galvin and Gagne 2013
19 Determining Length of Next CPU Burst Can only estimate the length should be similar to the previous one Then pick process with shortest predicted next CPU burst Can be done by using the length of previous CPU bursts, using exponential averaging t n actual length of n n 1 3., Define : Commonly, α set to ½ CPU burst predicted value for the next CPU th 1. n 1 tn n burst 6.19 Silberschatz, Galvin and Gagne 2013
20 Prediction of the Length of the Next CPU Burst 6.20 Silberschatz, Galvin and Gagne 2013
21 Examples of Exponential Averaging =0 =1 n+1 = n Recent history does not count n+1 = t n Only the actual last CPU burst counts If we expand the formula, we get: n+1 = t n +(1 - ) t n (1 - ) j t n -j + +(1 - ) n +1 0 Since both and (1 - ) are less than or equal to 1, each successive term has less weight than its predecessor 6.21 Silberschatz, Galvin and Gagne 2013
22 Shortest-remaining-time-first SJF algorithm can be either preemptive or nonpreemptive. Preemptive SJF scheduling is also called shortest-remaining-timefirst 6.22 Silberschatz, Galvin and Gagne 2013
23 Example of Shortest-remaining-time-first Now we add the concepts of varying arrival times and preemption to the analysis ProcessAarri Arrival TimeT Burst Time P P P P Preemptive SJF Gantt Chart P 1 P 2 P 4 P 1 P Average waiting time = [(10-1)+(1-1)+(17-2)+5-3)]/4 = 26/4 = 6.5 msec 6.23 Silberschatz, Galvin and Gagne 2013
24 Priority Scheduling A priority number (integer) is associated with each process Priority can be defined either internally or externally. The CPU is allocated to the process with the highest priority (smallest integer highest priority) Preemptive Nonpreemptive SJF is priority scheduling where priority is the inverse of predicted next CPU burst time Problem Starvation low priority processes may never execute Solution Aging as time progresses increase the priority of the process 6.24 Silberschatz, Galvin and Gagne 2013
25 Example of Priority Scheduling ProcessA arri Burst TimeT Priority P P P P P Priority scheduling Gantt Chart P 21 P 52 P 1 P 3 P Average waiting time = 8.2 msec 6.25 Silberschatz, Galvin and Gagne 2013
26 Check Out Line in a Grocery Store Single Server How to schedule? Preemptive or non-preemptive 6.26 Silberschatz, Galvin and Gagne 2013
27 Round Robin (RR) Each process gets a small unit of CPU time (time quantum q), usually milliseconds. After this time has elapsed, the process is preempted and added to the end of the ready queue. If the process terminates before the time quantum, the scheduler proceeds to the next process in 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. Timer interrupts every quantum to schedule next process Performance q large FIFO q small q must be large with respect to context switch, otherwise overhead is too high 6.27 Silberschatz, Galvin and Gagne 2013
28 Example of RR with Time Quantum = 4 Process Burst Time P 1 24 P 2 3 P 3 3 The Gantt chart is: P P 2 P 3 P 1 P 1 P 1 P P Typically, higher average turnaround than SJF, but better response q should be large compared to context switch time q usually 10ms to 100ms, context switch < 10 usec 6.28 Silberschatz, Galvin and Gagne 2013
29 Time Quantum and Context Switch Time The performance of RR algorithm depends heavily on the size of the time quantum Silberschatz, Galvin and Gagne 2013
30 Turnaround Time Varies With The Time Quantum 80% of CPU bursts should be shorter than q 6.30 Silberschatz, Galvin and Gagne 2013
31 Multilevel Queue Ready queue is partitioned into separate queues, eg: foreground (interactive) background (batch) Process permanently in a given queue Each queue has its own scheduling algorithm: foreground RR background FCFS Scheduling must be done between the queues: Fixed priority scheduling; (i.e., serve all from foreground then from background). Possibility of starvation. Time slice each queue gets a certain amount of CPU time which it can schedule amongst its processes; i.e., 80% to foreground in RR, and 20% to background in FCFS 6.31 Silberschatz, Galvin and Gagne 2013
32 Multilevel Queue Scheduling 6.32 Silberschatz, Galvin and Gagne 2013
33 Multilevel Feedback Queue A process can move between the various queues; aging can be implemented this way Multilevel-feedback-queue scheduler defined by the following parameters: number of queues scheduling algorithms for each queue method used to determine when to upgrade a process method used to determine when to demote a process method used to determine which queue a process will enter when that process needs service 6.33 Silberschatz, Galvin and Gagne 2013
34 Example of Multilevel Feedback Queue Three queues: Q 0 RR with time quantum 8 milliseconds Q 1 RR time quantum 16 milliseconds Q 2 FCFS Scheduling A new job enters queue Q 0 which is served FCFS When it gains CPU, job receives 8 milliseconds If it does not finish in 8 milliseconds, job is moved to queue Q 1 At Q 1 job is again served FCFS and receives 16 additional milliseconds If it still does not complete, it is preempted and moved to queue Q Silberschatz, Galvin and Gagne 2013
35 Multiple-Processor Scheduling CPU scheduling more complex when multiple CPUs are available Homogeneous processors within a multiprocessor Asymmetric multiprocessing only one processor accesses the system data structures, alleviating the need for data sharing Symmetric multiprocessing (SMP) each processor is selfscheduling, all processes in common ready queue, or each has its own private queue of ready processes Currently, most common 6.35 Silberschatz, Galvin and Gagne 2013
36 Processor Affinity Processor affinity process has affinity for processor on which it is currently running. Why? Consider what happens to cache memory when a process has been running on a specific processor. Successive memory accesses by the process are often satisfied in cache memory. When the process migrates to another processor, the cache for the second processor must be repopulated. soft affinity attempting to keep a process running on the same processor but not guaranteeing that it will do so. hard affinity allowing a process to specify that it is not to migrate to other processors. Variations including processor sets. The main-memory architecture of a system can also affect processor affinity issues. See next slide Silberschatz, Galvin and Gagne 2013
37 NUMA and CPU Scheduling Note that memory-placement algorithms can also consider affinity NUMA Non-uniform memory access 6.37 Silberschatz, Galvin and Gagne 2013
38 Multiple-Processor Scheduling Load Balancing If SMP, need to keep all CPUs loaded for efficiency Load balancing attempts to keep workload evenly distributed Push migration a specific task periodically checks load on each processor, and if found an imbalance, pushes task from overloaded CPU to other CPUs Pull migration idle processors pulls waiting task from busy processor 6.38 Silberschatz, Galvin and Gagne 2013
39 Real-Time CPU Scheduling Can present obvious challenges Soft real-time systems no guarantee as to when critical realtime process will be scheduled Hard real-time systems task must be serviced by its deadline Event Latency Antilock break system: 3-5 milliseconds Two types of latencies affect performance 1. Interrupt latency time from arrival of interrupt to start of routine that services interrupt. (interrupts can be disabled for only very short periods of time) 2. Dispatch latency time for scheduling dispatcher to take current process off CPU and switch to another 6.39 Silberschatz, Galvin and Gagne 2013
40 Real-Time CPU Scheduling (Cont.) Conflict phase of dispatch latency: 1. Preemption of any process running in kernel mode 2. Release by lowpriority process of resources needed by highpriority processes 6.40 Silberschatz, Galvin and Gagne 2013
41 Priority-based Scheduling For real-time scheduling, scheduler must support preemptive, prioritybased scheduling But only guarantees soft real-time For hard real-time must also provide ability to meet deadlines 6.41 Silberschatz, Galvin and Gagne 2013
42 Process Characteristics Processes have characteristics: periodic ones require CPU at constant intervals Has processing time t, deadline d, period p 0 t d p Rate of periodic task is 1/p 6.42 Silberschatz, Galvin and Gagne 2013
43 Rate Montonic Scheduling A priority is assigned based on the inverse of its period Shorter periods = higher priority; Longer periods = lower priority P 1 is assigned a higher priority than P 2. P1=50, t1=20 P2 = 100, t2= Silberschatz, Galvin and Gagne 2013
44 Missed Deadlines with Rate Monotonic Scheduling P1=50, t1=25 P2 = 80, t2= Silberschatz, Galvin and Gagne 2013
45 Earliest Deadline First Scheduling (EDF) Priorities are assigned according to deadlines: the earlier the deadline, the higher the priority; the later the deadline, the lower the priority P1=50, t1=25 P2 = 80, t2= Silberschatz, Galvin and Gagne 2013
46 Operating System Examples Linux scheduling Windows scheduling Solaris scheduling We skip these examples 6.46 Silberschatz, Galvin and Gagne 2013
47 Algorithm Evaluation How to select CPU-scheduling algorithm for an OS? Determine criteria, then evaluate algorithms Deterministic modeling Type of analytic evaluation Takes a particular predetermined workload and defines the performance of each algorithm for that workload Consider 5 processes arriving at time 0: 6.47 Silberschatz, Galvin and Gagne 2013
48 Deterministic Evaluation For each algorithm, calculate minimum average waiting time Simple and fast, but requires exact numbers for input, applies only to those inputs FCS is 28ms: Non-preemptive SFJ is 13ms: RR (quantum = 10) is 23ms: 6.48 Silberschatz, Galvin and Gagne 2013
49 Queueing Models Describes the arrival of processes, and CPU and I/O bursts probabilistically Commonly exponential, and described by mean Computes average throughput, utilization, waiting time, etc Computer system described as network of servers, each with queue of waiting processes Knowing arrival rates and service rates Computes utilization, average queue length, average wait time, etc 6.49 Silberschatz, Galvin and Gagne 2013
50 Little s Formula n = average queue length W = average waiting time in queue λ = average arrival rate into queue Little s law in steady state, processes leaving queue must equal processes arriving, thus: n = λ x W Valid for any scheduling algorithm and arrival distribution For example, if on average 7 processes arrive per second, and normally 14 processes in queue, then average wait time per process = 2 seconds 6.50 Silberschatz, Galvin and Gagne 2013
51 Simulations Queueing models limited Simulations more accurate Programmed model of computer system Clock is a variable Gather statistics indicating algorithm performance Data to drive simulation gathered via Random number generator according to probabilities Distributions defined mathematically or empirically Trace tapes record sequences of real events in real systems 6.51 Silberschatz, Galvin and Gagne 2013
52 Evaluation of CPU Schedulers by Simulation 6.52 Silberschatz, Galvin and Gagne 2013
53 Review and Exercise Exercise 6.3 Exercise 6.3 SJF preemptive scheduling Exercise Silberschatz, Galvin and Gagne 2013
54 End of Chapter 6 Silberschatz, Galvin and Gagne 2013
Chapter 6: CPU Scheduling. Operating System Concepts 9 th Edition
Chapter 6: CPU Scheduling Silberschatz, Galvin and Gagne 2013 Chapter 6: CPU Scheduling Basic Concepts Scheduling Criteria Scheduling Algorithms Thread Scheduling Multiple-Processor Scheduling Real-Time
More informationCPU Scheduling: Objectives
CPU Scheduling: Objectives CPU scheduling, the basis for multiprogrammed operating systems CPU-scheduling algorithms Evaluation criteria for selecting a CPU-scheduling algorithm for a particular system
More informationLECTURE 3:CPU SCHEDULING
LECTURE 3:CPU SCHEDULING 1 Outline Basic Concepts Scheduling Criteria Scheduling Algorithms Multiple-Processor Scheduling Real-Time CPU Scheduling Operating Systems Examples Algorithm Evaluation 2 Objectives
More informationCPU Scheduling. Daniel Mosse. (Most slides are from Sherif Khattab and Silberschatz, Galvin and Gagne 2013)
CPU Scheduling Daniel Mosse (Most slides are from Sherif Khattab and Silberschatz, Galvin and Gagne 2013) Basic Concepts Maximum CPU utilization obtained with multiprogramming CPU I/O Burst Cycle Process
More informationCS370 Operating Systems
CS370 Operating Systems Colorado State University Yashwant K Malaiya Fall 2017 Lecture 10 Slides based on Text by Silberschatz, Galvin, Gagne Various sources 1 1 Chapter 6: CPU Scheduling Basic Concepts
More informationChapter 5: CPU Scheduling. Operating System Concepts Essentials 8 th Edition
Chapter 5: CPU Scheduling Silberschatz, Galvin and Gagne 2011 Chapter 5: CPU Scheduling Basic Concepts Scheduling Criteria Scheduling Algorithms Thread Scheduling Multiple-Processor Scheduling Operating
More informationCS370 Operating Systems
CS370 Operating Systems Colorado State University Yashwant K Malaiya Spring 2019 Lecture 8 Scheduling Slides based on Text by Silberschatz, Galvin, Gagne Various sources 1 1 FAQ POSIX: Portable Operating
More informationChapter 5: CPU Scheduling
Chapter 5: CPU Scheduling Chapter 5: CPU Scheduling Basic Concepts Scheduling Criteria Scheduling Algorithms Thread Scheduling Multiple-Processor Scheduling Operating Systems Examples Algorithm Evaluation
More informationLecture 5 / Chapter 6 (CPU Scheduling) Basic Concepts. Scheduling Criteria Scheduling Algorithms
Operating System Lecture 5 / Chapter 6 (CPU Scheduling) Basic Concepts Scheduling Criteria Scheduling Algorithms OS Process Review Multicore Programming Multithreading Models Thread Libraries Implicit
More informationCS307: Operating Systems
CS307: Operating Systems Chentao Wu 吴晨涛 Associate Professor Dept. of Computer Science and Engineering Shanghai Jiao Tong University SEIEE Building 3-513 wuct@cs.sjtu.edu.cn Download Lectures ftp://public.sjtu.edu.cn
More informationChapter 5: CPU Scheduling
Chapter 5: CPU Scheduling Basic Concepts Scheduling Criteria Scheduling Algorithms Thread Scheduling Multiple-Processor Scheduling Operating Systems Examples Algorithm Evaluation Chapter 5: CPU Scheduling
More informationCPU Scheduling. Operating Systems (Fall/Winter 2018) Yajin Zhou ( Zhejiang University
Operating Systems (Fall/Winter 2018) CPU Scheduling Yajin Zhou (http://yajin.org) Zhejiang University Acknowledgement: some pages are based on the slides from Zhi Wang(fsu). Review Motivation to use threads
More informationChapter 6: CPU Scheduling. Operating System Concepts 9 th Edition
Chapter 6: CPU Scheduling Silberschatz, Galvin and Gagne 2013 Objectives To introduce CPU scheduling, which is the basis for multiprogrammed operating systems To describe various CPU-scheduling algorithms
More informationChapter 6: CPU Scheduling
Chapter 6: CPU Scheduling Chapter 6: CPU Scheduling Basic Concepts Scheduling Criteria Scheduling Algorithms Thread Scheduling Multiple-Processor Scheduling Real-Time CPU Scheduling Operating Systems Examples
More informationChapter 6: CPU Scheduling. Operating System Concepts 9 th Edition
Chapter 6: CPU Scheduling Silberschatz, Galvin and Gagne 2013 Chapter 6: CPU Scheduling Basic Concepts Scheduling Criteria Scheduling Algorithms Thread Scheduling Multiple-Processor Scheduling Real-Time
More informationChapter 6: CPU Scheduling
Chapter 6: CPU Scheduling Basic Concepts Scheduling Criteria Scheduling Algorithms Multiple-Processor Scheduling Real-Time Scheduling Thread Scheduling Operating Systems Examples Java Thread Scheduling
More informationProperties of Processes
CPU Scheduling Properties of Processes CPU I/O Burst Cycle Process execution consists of a cycle of CPU execution and I/O wait. CPU burst distribution: CPU Scheduler Selects from among the processes that
More informationChapter 6: CPU Scheduling
Chapter 6: CPU Scheduling Silberschatz, Galvin and Gagne 2013 Chapter 6: CPU Scheduling Basic Concepts Scheduling Criteria Scheduling Algorithms Thread Scheduling Multiple-Processor Scheduling Real-Time
More informationOperating Systems CS 323 Ms. Ines Abbes
Taibah University College of Community of Badr Computer Science Department Operating Systems CS71/CS72 جامعة طيبة كلية المجتمع ببدر قسم علوم الحاسب مقرر: نظم التشغيل Operating Systems CS 323 Ms. Ines Abbes
More informationCPU Scheduling. Basic Concepts. Histogram of CPU-burst Times. Dispatcher. CPU Scheduler. Alternating Sequence of CPU and I/O Bursts
CS307 Basic Concepts Maximize CPU utilization obtained with multiprogramming CPU Scheduling CPU I/O Burst Cycle Process execution consists of a cycle of CPU execution and I/O wait CPU burst distribution
More informationCPU Scheduling Algorithms
CPU Scheduling Algorithms Notice: The slides for this lecture have been largely based on those accompanying the textbook Operating Systems Concepts with Java, by Silberschatz, Galvin, and Gagne (2007).
More informationChapter 5 CPU scheduling
Chapter 5 CPU scheduling Contents Basic Concepts Scheduling Criteria Scheduling Algorithms Multiple-Processor Scheduling Real-Time Scheduling Thread Scheduling Operating Systems Examples Java Thread Scheduling
More informationChapter 5: Process Scheduling
Chapter 5: Process Scheduling Chapter 5: Process Scheduling Basic Concepts Scheduling Criteria Scheduling Algorithms Multiple-Processor Scheduling Thread Scheduling Operating Systems Examples Algorithm
More informationCHAPTER 2: PROCESS MANAGEMENT
1 CHAPTER 2: PROCESS MANAGEMENT Slides by: Ms. Shree Jaswal TOPICS TO BE COVERED Process description: Process, Process States, Process Control Block (PCB), Threads, Thread management. Process Scheduling:
More informationCSE 4/521 Introduction to Operating Systems
CSE 4/521 Introduction to Operating Systems Lecture 9 CPU Scheduling II (Scheduling Algorithms, Thread Scheduling, Real-time CPU Scheduling) Summer 2018 Overview Objective: 1. To describe priority scheduling
More informationChapter 5: Process Scheduling
Chapter 5: Process Scheduling Chapter 5: Process Scheduling Basic Concepts Scheduling Criteria Scheduling Algorithms Thread Scheduling Multiple-Processor Scheduling Real-Time CPU Scheduling Operating Systems
More informationChapter 5: CPU Scheduling
COP 4610: Introduction to Operating Systems (Fall 2016) Chapter 5: CPU Scheduling Zhi Wang Florida State University Contents Basic concepts Scheduling criteria Scheduling algorithms Thread scheduling Multiple-processor
More informationChapter 6: CPU Scheduling. Operating System Concepts 9 th Edition
Chapter 6: CPU Scheduling Silberschatz, Galvin and Gagne 2013 Chapter 6: CPU Scheduling Basic Concepts Scheduling Criteria Scheduling Algorithms Thread Scheduling Multiple-Processor Scheduling Real-Time
More informationChapter 5: CPU Scheduling. Operating System Concepts 8 th Edition,
Chapter 5: CPU Scheduling Operating System Concepts 8 th Edition, Hanbat National Univ. Computer Eng. Dept. Y.J.Kim 2009 Chapter 5: Process Scheduling Basic Concepts Scheduling Criteria Scheduling Algorithms
More informationTDIU25: Operating Systems II. Processes, Threads and Scheduling
TDIU25: Operating Systems II. Processes, Threads and Scheduling SGG9: 3.1-3.3, 4.1-4.3, 5.1-5.4 o Process concept: context switch, scheduling queues, creation o Multithreaded programming o Process scheduling
More informationCS370 Operating Systems
CS370 Operating Systems Colorado State University Yashwant K Malaiya Fall 2017 Lecture 9 Slides based on Text by Silberschatz, Galvin, Gagne Various sources 1 1 CPU Scheduling: Objectives CPU scheduling,
More informationUniprocessor Scheduling. Basic Concepts Scheduling Criteria Scheduling Algorithms. Three level scheduling
Uniprocessor Scheduling Basic Concepts Scheduling Criteria Scheduling Algorithms Three level scheduling 2 1 Types of Scheduling 3 Long- and Medium-Term Schedulers Long-term scheduler Determines which programs
More informationOperating System Concepts Ch. 5: Scheduling
Operating System Concepts Ch. 5: Scheduling Silberschatz, Galvin & Gagne Scheduling In a multi-programmed system, multiple processes may be loaded into memory at the same time. We need a procedure, or
More informationChapter 6: CPU Scheduling
Chapter 6: CPU Scheduling Silberschatz, Galvin and Gagne Histogram of CPU-burst Times 6.2 Silberschatz, Galvin and Gagne Alternating Sequence of CPU And I/O Bursts 6.3 Silberschatz, Galvin and Gagne CPU
More informationProcesses. CS 475, Spring 2018 Concurrent & Distributed Systems
Processes CS 475, Spring 2018 Concurrent & Distributed Systems Review: Abstractions 2 Review: Concurrency & Parallelism 4 different things: T1 T2 T3 T4 Concurrency: (1 processor) Time T1 T2 T3 T4 T1 T1
More informationCS370 Operating Systems
CS370 Operating Systems Colorado State University Yashwant K Malaiya Spring 2018 Lecture 8 Threads and Scheduling Slides based on Text by Silberschatz, Galvin, Gagne Various sources 1 1 FAQ How many threads
More informationChapter 5 Process Scheduling
Chapter 5 Process Scheduling Da-Wei Chang CSIE.NCKU Source: Abraham Silberschatz, Peter B. Galvin, and Greg Gagne, "Operating System Concepts", 9th Edition, Wiley. 1 Outline Basic Concepts Scheduling Criteria
More informationOPERATING SYSTEMS CS3502 Spring Processor Scheduling. Chapter 5
OPERATING SYSTEMS CS3502 Spring 2018 Processor Scheduling Chapter 5 Goals of Processor Scheduling Scheduling is the sharing of the CPU among the processes in the ready queue The critical activities are:
More informationChapter 5: CPU Scheduling. Operating System Concepts 9 th Edit9on
Chapter 5: CPU Scheduling Operating System Concepts 9 th Edit9on Silberschatz, Galvin and Gagne 2013 Chapter 6: CPU Scheduling 1. Basic Concepts 2. Scheduling Criteria 3. Scheduling Algorithms 4. Thread
More informationCPU Scheduling. Rab Nawaz Jadoon. Assistant Professor DCS. Pakistan. COMSATS, Lahore. Department of Computer Science
CPU Scheduling Rab Nawaz Jadoon DCS COMSATS Institute of Information Technology Assistant Professor COMSATS, Lahore Pakistan Operating System Concepts Objectives To introduce CPU scheduling, which is the
More informationCh 4 : CPU scheduling
Ch 4 : CPU scheduling It's the basis of multiprogramming operating systems. By switching the CPU among processes, the operating system can make the computer more productive In a single-processor system,
More informationProcess- Concept &Process Scheduling OPERATING SYSTEMS
OPERATING SYSTEMS Prescribed Text Book Operating System Principles, Seventh Edition By Abraham Silberschatz, Peter Baer Galvin and Greg Gagne PROCESS MANAGEMENT Current day computer systems allow multiple
More informationStart of Lecture: February 10, Chapter 6: Scheduling
Start of Lecture: February 10, 2014 1 Reminders Exercise 2 due this Wednesday before class Any questions or comments? 2 Scheduling so far First-Come-First Serve FIFO scheduling in queue without preempting
More informationOperating Systems Unit 3
Unit 3 CPU Scheduling Algorithms Structure 3.1 Introduction Objectives 3.2 Basic Concepts of Scheduling. CPU-I/O Burst Cycle. CPU Scheduler. Preemptive/non preemptive scheduling. Dispatcher Scheduling
More informationCS3733: Operating Systems
CS3733: Operating Systems Topics: Process (CPU) Scheduling (SGG 5.1-5.3, 6.7 and web notes) Instructor: Dr. Dakai Zhu 1 Updates and Q&A Homework-02: late submission allowed until Friday!! Submit on Blackboard
More informationPractice Exercises 305
Practice Exercises 305 The FCFS algorithm is nonpreemptive; the RR algorithm is preemptive. The SJF and priority algorithms may be either preemptive or nonpreemptive. Multilevel queue algorithms allow
More informationCPU Scheduling. CSE 2431: Introduction to Operating Systems Reading: Chapter 6, [OSC] (except Sections )
CPU Scheduling CSE 2431: Introduction to Operating Systems Reading: Chapter 6, [OSC] (except Sections 6.7.2 6.8) 1 Contents Why Scheduling? Basic Concepts of Scheduling Scheduling Criteria A Basic Scheduling
More informationOPERATING SYSTEMS. UNIT II Sections A, B & D. An operating system executes a variety of programs:
OPERATING SYSTEMS UNIT II Sections A, B & D PREPARED BY ANIL KUMAR PRATHIPATI, ASST. PROF., DEPARTMENT OF CSE. PROCESS CONCEPT An operating system executes a variety of programs: Batch system jobs Time-shared
More informationLecture 2 Process Management
Lecture 2 Process Management Process Concept An operating system executes a variety of programs: Batch system jobs Time-shared systems user programs or tasks The terms job and process may be interchangeable
More informationCS370: System Architecture & Software [Fall 2014] Dept. Of Computer Science, Colorado State University
Frequently asked questions from the previous class survey CS 370: SYSTEM ARCHITECTURE & SOFTWARE [CPU SCHEDULING] Shrideep Pallickara Computer Science Colorado State University OpenMP compiler directives
More informationSo far. Next: scheduling next process from Wait to Run. 1/31/08 CSE 30341: Operating Systems Principles
So far. Firmware identifies hardware devices present OS bootstrap process: uses the list created by firmware and loads driver modules for each detected hardware. Initializes internal data structures (PCB,
More information3. CPU Scheduling. Operating System Concepts with Java 8th Edition Silberschatz, Galvin and Gagn
3. CPU Scheduling Operating System Concepts with Java 8th Edition Silberschatz, Galvin and Gagn S P O I L E R operating system CPU Scheduling 3 operating system CPU Scheduling 4 Long-short-medium Scheduler
More informationChap 7, 8: Scheduling. Dongkun Shin, SKKU
Chap 7, 8: Scheduling 1 Introduction Multiprogramming Multiple processes in the system with one or more processors Increases processor utilization by organizing processes so that the processor always has
More informationScheduling. Today. Next Time Process interaction & communication
Scheduling Today Introduction to scheduling Classical algorithms Thread scheduling Evaluating scheduling OS example Next Time Process interaction & communication Scheduling Problem Several ready processes
More informationCourse Syllabus. Operating Systems
Course Syllabus. Introduction - History; Views; Concepts; Structure 2. Process Management - Processes; State + Resources; Threads; Unix implementation of Processes 3. Scheduling Paradigms; Unix; Modeling
More informationCS370 Operating Systems
CS370 Operating Systems Colorado State University Yashwant K Malaiya Spring 1018 L10 Synchronization Slides based on Text by Silberschatz, Galvin, Gagne Various sources 1 1 FAQ Development project: You
More informationCOSC243 Part 2: Operating Systems
COSC243 Part 2: Operating Systems Lecture 17: CPU Scheduling Zhiyi Huang Dept. of Computer Science, University of Otago Zhiyi Huang (Otago) COSC243 Lecture 17 1 / 30 Overview Last lecture: Cooperating
More informationScheduling of processes
Scheduling of processes Processor scheduling Schedule processes on the processor to meet system objectives System objectives: Assigned processes to be executed by the processor Response time Throughput
More informationAnnouncements. Program #1. Program #0. Reading. Is due at 9:00 AM on Thursday. Re-grade requests are due by Monday at 11:59:59 PM.
Program #1 Announcements Is due at 9:00 AM on Thursday Program #0 Re-grade requests are due by Monday at 11:59:59 PM Reading Chapter 6 1 CPU Scheduling Manage CPU to achieve several objectives: maximize
More informationChap 7, 8: Scheduling. Dongkun Shin, SKKU
Chap 7, 8: Scheduling 1 Introduction Multiprogramming Multiple processes in the system with one or more processors Increases processor utilization by organizing processes so that the processor always has
More informationScheduling in the Supermarket
Scheduling in the Supermarket Consider a line of people waiting in front of the checkout in the grocery store. In what order should the cashier process their purchases? Scheduling Criteria CPU utilization
More informationby Maria Lima Term Paper for Professor Barrymore Warren Mercy College Division of Mathematics and Computer Information Science
by Maria Lima Term Paper for Professor Barrymore Warren Mercy College Division of Mathematics and Computer Information Science Table of Contents 1. Introduction...1 2. CPU Scheduling Overview...1 3. Processes
More informationScheduling. The Basics
The Basics refers to a set of policies and mechanisms to control the order of work to be performed by a computer system. Of all the resources in a computer system that are scheduled before use, the CPU
More informationFrequently asked questions from the previous class survey
CS 370: OPERATING SYSTEMS [CPU SCHEDULING] Shrideep Pallickara Computer Science Colorado State University L14.1 Frequently asked questions from the previous class survey Turnstiles: Queue for threads blocked
More informationCPU scheduling. Alternating sequence of CPU and I/O bursts. P a g e 31
CPU scheduling CPU scheduling is the basis of multiprogrammed operating systems. By switching the CPU among processes, the operating system can make the computer more productive. In a single-processor
More informationRound Robin (RR) ACSC 271 Operating Systems. RR Example. RR Scheduling. Lecture 9: Scheduling Algorithms
Round Robin (RR) ACSC 271 Operating Systems Lecture 9: Scheduling Algorithms Each process gets a small unit of CPU time (time quantum), usually 10-100 milliseconds. After this time has elapsed, the process
More informationJob Scheduling. CS170 Fall 2018
Job Scheduling CS170 Fall 2018 What to Learn? Algorithms of job scheduling, which maximizes CPU utilization obtained with multiprogramming Select from ready processes and allocates the CPU to one of them
More informationPreview. Process Scheduler. Process Scheduling Algorithms for Batch System. Process Scheduling Algorithms for Interactive System
Preview Process Scheduler Short Term Scheduler Long Term Scheduler Process Scheduling Algorithms for Batch System First Come First Serve Shortest Job First Shortest Remaining Job First Process Scheduling
More informationLecture Topics. Announcements. Today: Uniprocessor Scheduling (Stallings, chapter ) Next: Advanced Scheduling (Stallings, chapter
Lecture Topics Today: Uniprocessor Scheduling (Stallings, chapter 9.1-9.3) Next: Advanced Scheduling (Stallings, chapter 10.1-10.4) 1 Announcements Self-Study Exercise #10 Project #8 (due 11/16) Project
More informationCPU Scheduling (1) CPU Scheduling (Topic 3) CPU Scheduling (2) CPU Scheduling (3) Resources fall into two classes:
CPU Scheduling (Topic 3) 홍성수 서울대학교공과대학전기공학부 Real-Time Operating Systems Laboratory CPU Scheduling (1) Resources fall into two classes: Preemptible: Can take resource away, use it for something else, then
More informationChapter 5 Scheduling
Chapter 5 Scheduling Images from Silberschatz Pacific University 1 Life time of a single process CPU usage/io bursts What would an IO bound process look like? What would a CPU bound process look like?
More informationALL the assignments (A1, A2, A3) and Projects (P0, P1, P2) we have done so far.
Midterm Exam Reviews ALL the assignments (A1, A2, A3) and Projects (P0, P1, P2) we have done so far. Particular attentions on the following: System call, system kernel Thread/process, thread vs process
More informationCPU Scheduling: Part I ( 5, SGG) Operating Systems. Autumn CS4023
Operating Systems Autumn 2017-2018 Outline 1 CPU Scheduling: Part I ( 5, SGG) Outline CPU Scheduling: Part I ( 5, SGG) 1 CPU Scheduling: Part I ( 5, SGG) Basic Concepts Typical program behaviour CPU Scheduling:
More information8: Scheduling. Scheduling. Mark Handley
8: Scheduling Mark Handley Scheduling On a multiprocessing system, more than one process may be available to run. The task of deciding which process to run next is called scheduling, and is performed by
More informationUnit 3 : Process Management
Unit : Process Management Processes are the most widely used units of computation in programming and systems, although object and threads are becoming more prominent in contemporary systems. Process management
More informationCPU Scheduling. Schedulers. CPSC 313: Intro to Computer Systems. Intro to Scheduling. Schedulers in the OS
Schedulers in the OS Scheduling Structure of a Scheduler Scheduling = Selection + Dispatching Criteria for scheduling Scheduling Algorithms FIFO/FCFS SPF / SRTF Priority - Based Schedulers start long-term
More informationTitolo presentazione. Scheduling. sottotitolo A.Y Milano, XX mese 20XX ACSO Tutoring MSc Eng. Michele Zanella
Titolo presentazione Scheduling sottotitolo A.Y. 2017-18 Milano, XX mese 20XX ACSO Tutoring MSc Eng. Michele Zanella Process Scheduling Goals: Multiprogramming: having some process running at all times,
More informationMaximum CPU utilization obtained with multiprogramming. CPU I/O Burst Cycle Process execution consists of a cycle of CPU execution and I/O wait
Basic Concepts Scheduling Criteria Scheduling Algorithms Multiple-Processor Scheduling Real-Time Scheduling Thread Scheduling Operating Systems Examples Java Thread Scheduling Algorithm Evaluation CPU
More informationLast class: Today: CPU Scheduling. CPU Scheduling Algorithms and Systems
1 Last class: CPU Scheduling Today: CPU Scheduling Algorithms and Systems 2 Scheduling Algorithms First-come, First-serve (FCFS) Non-preemptive Does not account for waiting time (or much else) Convoy problem
More informationChapter 9 Uniprocessor Scheduling
Operating Systems: Internals and Design Principles, 6/E William Stallings Chapter 9 Uniprocessor Scheduling Patricia Roy Manatee Community College, Venice, FL 2008, Prentice Hall Aim of Scheduling Assign
More informationCISC 7310X. C05: CPU Scheduling. Hui Chen Department of Computer & Information Science CUNY Brooklyn College. 3/1/2018 CUNY Brooklyn College
CISC 7310X C05: CPU Scheduling Hui Chen Department of Computer & Information Science CUNY Brooklyn College 3/1/2018 CUNY Brooklyn College 1 Outline Recap & issues CPU Scheduling Concepts Goals and criteria
More informationCSC Operating Systems Spring Lecture - XII Midterm Review. Tevfik Ko!ar. Louisiana State University. March 4 th, 2008.
CSC 4103 - Operating Systems Spring 2008 Lecture - XII Midterm Review Tevfik Ko!ar Louisiana State University March 4 th, 2008 1 I/O Structure After I/O starts, control returns to user program only upon
More informationCSE120 Principles of Operating Systems. Prof Yuanyuan (YY) Zhou Scheduling
CSE120 Principles of Operating Systems Prof Yuanyuan (YY) Zhou Scheduling Announcement l Homework 2 due on October 26th l Project 1 due on October 27th 2 Scheduling Overview l In discussing process management
More informationCS370 Operating Systems Midterm Review
CS370 Operating Systems Midterm Review Yashwant K Malaiya Fall 2015 Slides based on Text by Silberschatz, Galvin, Gagne 1 1 What is an Operating System? An OS is a program that acts an intermediary between
More informationUniprocessor Scheduling. Aim of Scheduling
Uniprocessor Scheduling Chapter 9 Aim of Scheduling Response time Throughput Processor efficiency Types of Scheduling Long-Term Scheduling Determines which programs are admitted to the system for processing
More informationUniprocessor Scheduling. Aim of Scheduling. Types of Scheduling. Long-Term Scheduling. Chapter 9. Response time Throughput Processor efficiency
Uniprocessor Scheduling Chapter 9 Aim of Scheduling Response time Throughput Processor efficiency Types of Scheduling Long-Term Scheduling Determines which programs are admitted to the system for processing
More informationCPU Scheduling (Part II)
CPU Scheduling (Part II) Amir H. Payberah amir@sics.se Amirkabir University of Technology (Tehran Polytechnic) Amir H. Payberah (Tehran Polytechnic) CPU Scheduling 1393/7/28 1 / 58 Motivation Amir H. Payberah
More informationChapter 9. Uniprocessor Scheduling
Operating System Chapter 9. Uniprocessor Scheduling Lynn Choi School of Electrical Engineering Scheduling Processor Scheduling Assign system resource (CPU time, IO device, etc.) to processes/threads to
More informationSubject Name: OPERATING SYSTEMS. Subject Code: 10EC65. Prepared By: Kala H S and Remya R. Department: ECE. Date:
Subject Name: OPERATING SYSTEMS Subject Code: 10EC65 Prepared By: Kala H S and Remya R Department: ECE Date: Unit 7 SCHEDULING TOPICS TO BE COVERED Preliminaries Non-preemptive scheduling policies Preemptive
More informationLast Class: Processes
Last Class: Processes A process is the unit of execution. Processes are represented as Process Control Blocks in the OS PCBs contain process state, scheduling and memory management information, etc A process
More informationCPU Scheduling. The scheduling problem: When do we make decision? - Have K jobs ready to run - Have N 1 CPUs - Which jobs to assign to which CPU(s)
1/32 CPU Scheduling The scheduling problem: - Have K jobs ready to run - Have N 1 CPUs - Which jobs to assign to which CPU(s) When do we make decision? 2/32 CPU Scheduling Scheduling decisions may take
More informationOperating Systems. Process scheduling. Thomas Ropars.
1 Operating Systems Process scheduling Thomas Ropars thomas.ropars@univ-grenoble-alpes.fr 2018 References The content of these lectures is inspired by: The lecture notes of Renaud Lachaize. The lecture
More informationAnnouncements. Program #1. Reading. Due 2/15 at 5:00 pm. Finish scheduling Process Synchronization: Chapter 6 (8 th Ed) or Chapter 7 (6 th Ed)
Announcements Program #1 Due 2/15 at 5:00 pm Reading Finish scheduling Process Synchronization: Chapter 6 (8 th Ed) or Chapter 7 (6 th Ed) 1 Scheduling criteria Per processor, or system oriented CPU utilization
More informationAssignment 3 (Due date: Thursday, 10/15/2009, in class) Part One: Provide brief answers to the following Chapter Exercises questions:
Assignment 3 (Due date: Thursday, 10/15/2009, in class) Your name: Date: Part One: Provide brief answers to the following Chapter Exercises questions: 4.7 Provide two programming examples in which multithreading
More informationCS 326: Operating Systems. CPU Scheduling. Lecture 6
CS 326: Operating Systems CPU Scheduling Lecture 6 Today s Schedule Agenda? Context Switches and Interrupts Basic Scheduling Algorithms Scheduling with I/O Symmetric multiprocessing 2/7/18 CS 326: Operating
More informationOperating Systems ECE344. Ding Yuan
Operating Systems ECE344 Ding Yuan Announcement & Reminder Midterm exam Will grade them this Friday Will post the solution online before next lecture Will briefly go over the common mistakes next Monday
More informationA COMPARATIVE STUDY OF CPU SCHEDULING POLICIES IN OPERATING SYSTEMS
VSRD International Journal of Computer Science &Information Technology, Vol. IV Issue VII July 2014 / 119 e-issn : 2231-2471, p-issn : 2319-2224 VSRD International Journals : www.vsrdjournals.com REVIEW
More informationScheduling. Scheduling 1/51
Scheduling 1/51 Learning Objectives Scheduling To understand the role of a scheduler in an operating system To understand the scheduling mechanism To understand scheduling strategies such as non-preemptive
More informationChapter 19: Real-Time Systems. Operating System Concepts 8 th Edition,
Chapter 19: Real-Time Systems, Silberschatz, Galvin and Gagne 2009 Chapter 19: Real-Time Systems System Characteristics Features of Real-Time Systems Implementing Real-Time Operating Systems Real-Time
More informationUniprocessor Scheduling
Uniprocessor Scheduling Chapter 9 Operating Systems: Internals and Design Principles, 6/E William Stallings Patricia Roy Manatee Community College, Venice, FL 2008, Prentice Hall CPU- and I/O-bound processes
More information