This document discusses key concepts in process scheduling. It explains that the goal of multiprogramming is to maximize CPU utilization by reducing idle time when processes are waiting for I/O. It describes how processes alternate between CPU bursts and I/O waits in a cycle. Scheduling can be preemptive or nonpreemptive. Common scheduling algorithms like FCFS, SJF, priority, and round-robin are explained. The document also covers multilevel queue scheduling, multilevel feedback queue scheduling, and concepts for scheduling on multiprocessor systems.
Types of loading, production & operations managementMahima Mutnuru
Types of Loading-
Infinite Loading
Finite Loading
Also know about Scheduling as Loading is an vital part of Scheduling.
Explained with examples.
Important concept in Production and Operation Management.
Types of loading, production & operations managementMahima Mutnuru
Types of Loading-
Infinite Loading
Finite Loading
Also know about Scheduling as Loading is an vital part of Scheduling.
Explained with examples.
Important concept in Production and Operation Management.
Sara Afshar: Scheduling and Resource Sharing in Multiprocessor Real-Time Systemsknowdiff
PhD Candidate,
Department of Computer science
Mälardalen University
Time: Tuesday, Dec. 30, 2014, 11:30 a.m.
Location: Computer Engineering Department, Urmia University
Abstract:
The processor is the brain of a computer system. Usually, one or more programs run on a processor where each program is typically responsible for performing a particular task or function of the system. The performance of all the tasks together results in the system functionality. In many computer systems, it is not only enough that all tasks deliver correct output, but it is also crucial that these activities are delivered in a proper time. This type of systems that have timing requirements are known as real-time systems. A scheduler is responsible for scheduling all tasks on the processor, i.e., it dictates which task to run and when to run to ensure that all tasks are carried out on time. Typically, such tasks/programs need to use the computer system’s hardware and software resources to perform their calculation. Examples of such type of resources that are shared among programs are I/O devices, buffers and memories. Technology that is used for the management of shared resources is known as resource sharing synchronization protocol.
In recent years, a shift from single-processor platforms to multiprocessor platforms has become inevitable due to availability of processor chips and requirements on increased performance. Scheduling and resource sharing protocols have been well studied for uniprocessor systems. However, in the context of multiprocessors, still such techniques are not fully mature. The shift towards multi-core technology has revealed the demand for real-time scheduling algorithms along with synchronization protocols to support real-time applications on multiprocessors, both with and without dependencies.
In this talk, we first have an introduction to real-time embedded systems. Next, we look at scheduling and resource sharing policies in uniprocessor platforms. Further, we discuss the extension of scheduling and resource sharing policies for multiprocessor platforms and present the recent challenges arisen in this context.
Biography:
Sara Afshar is a PhD student at Mälardalen University. She has received her B.Sc. degree in Electrical Engineering from Tabriz University, Iran in 2002. She worked at different engineering companies until 2009. In the year 2010 she started her M.Sc. in Embedded Systems at Mälardalen University. She obtained her Master degree in 2012 and at the same year she started her PhD studies in Mälardalen University. Currently she is working on the topic of resource sharing in multiprocessor systems. She is part of the Complex Real-Time Embedded Systems group at Mälardalen University.
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
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Executive Directors Chat Leveraging AI for Diversity, Equity, and InclusionTechSoup
Let’s explore the intersection of technology and equity in the final session of our DEI series. Discover how AI tools, like ChatGPT, can be used to support and enhance your nonprofit's DEI initiatives. Participants will gain insights into practical AI applications and get tips for leveraging technology to advance their DEI goals.
Macroeconomics- Movie Location
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2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
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Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
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This slide is special for master students (MIBS & MIFB) in UUM. Also useful for readers who are interested in the topic of contemporary Islamic banking.
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A Strategic Approach: GenAI in EducationPeter Windle
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2. Basic concept
In a single-processor system only one process can run at a
time. Other active processes wait their turn until the CPU is
free.
●
The main purpose of the multiprogramming is to have
process running at all times, in order to maximize CPU
utilization.
●
Maximization is achieved by reducing the idle time of a
process while waits for the completion of some I/O request
●
Operating System 2011/2012
3. CPU – I/O Burst Cycle
●
●
●
The process execution
process execution consists of a
cycle of CPU execution and
I/O wait.
The duration of the CPU
execution and the I/O wait
depend on the process type.
Processes are divided in
●
CPU bounded
●
I/O bounded
Operating System 2011/2012
4. CPU Scheduler
A new process is scheduled by the CPU when the previous one:
1. switches from the running state to the waiting state,
2. switches from the running state to the ready state
3. switches from the waiting state to the ready state
4. terminates
●
●
●
When scheduling takes place only under circumstances 1 and 4,
we say that the scheduling scheme is nonpreemptive or
cooperative, otherwise, it is preemptive.
At the nonpreemptive scheduling is the process that
autonomously releases the resource.
At the preemptive scheduling is the scheduler that forces the
process to interrupt and release the resource.
Operating System 2011/2012
5. Dispatcher
The dispatcher is the module that gives the control of the
CPU to the process selected by the short-term scheduler.
This module is responsible of the process switch:
●
collects the information of one process to stop
●
store the process stack
●
load the next process stack
●
give control to the CPU
The time the dispatcher takes to stop one process and
start another process of the queue is called dispatch latency.
Operating System 2011/2012
6. Scheduling Criteria
The criteria used by the algorithms to evaluate the efficiency are:
●
●
●
●
●
CPU utilization: % of time where the CPU is busy.
Throughput: number of processes that are completed per time
unit (from mm to h).
Turnaround time: is 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: is the sum of the periods spent waiting in the ready
queue.
Response time: is the time from the submission of a request until
the first response is produced.
Operating System 2011/2012
8. First-Come, First-Served (FCFS)
●
Simplest CPU-scheduling algorithm.
●
The process that requests the CPU first is allocated the CPU
first (managed by the FIFO queue) .
●
( + ) The code for FCFS scheduling is simple to write and
understand.
●
( - ) The average waiting time under the FCFS policy is often
quite long.
Operating System 2011/2012
9. First-Come, First-Served (FCFS)
Suppose that the processes arrive in the order: P1 , P2 , P3,
with the respective computation time: 24, 3, 3.
Waiting time for:
●
P1 = 0 – no process to wait;
●
P2 = 24 – starts after P1;
●
P3 = 27 – starts after P1 and P2;
Average waiting time: (0 + 24 + 27)/3 = 17
Operating System 2011/2012
10. First-Come, First-Served (FCFS)
Suppose that the processes arrive in the order P2 , P3 , P1 with
the respective computation time: 3, 3, 24.
Waiting time for:
●
P2 = 0 – no process to wait;
●
P3 = 3 – starts after P2;
●
P1 = 6 – starts after P2 and P3;
Average waiting time: (0 + 3 + 6) / 3 = 3
Operating System 2011/2012
11. First-Come, First-Served (FCFS)
FCFS is non-preemptive
●
Not good for time sharing systems where where each user
needs to get a share of the CPU at regular intervals.
●
Convoy effect short process(I/O bound) wait for one long
CPU-bound process to complete a CPU burst before they get
a turn
●
➢
➢
➢
➢
➢
lowers CPU and device utilization
I/O bound processes complete their burst and enter ready queue –
I/O devices idle and I/O bound processes waiting
CPU bound process completes CPU burst and moves to I/O device
I/O bound processes all quickly complete their CPU bursts and enter
I/O queue – now CPU is idle
CPU bound completes I/O and executes on CPU; back to step 1
Operating System 2011/2012
12. Shortest-Job-First (SJF)
Shortest-Next-CPU-Burst algorithm.
●
This algorithm associates with each process the length of the
process’s next CPU burst.
●
If the next CPU bursts of two processes are the same, FCFS
scheduling is used.
●
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-RemainingTime-First (SRTF).
SJF is optimal – gives minimum average waiting time for a
given set of processes.
Operating System 2011/2012
13. Shortest-Job-First (SJF)
Suppose that the processes arrive in the order: P1 , P2 , P3, P4
with the respective computation time: 6, 8, 7, 3.
Waiting time for:
●
P4 = 0 – no process to wait;
●
P1 = 3 – starts after P4;
●
P3 = 9 – starts after P4 and P1;
●
P2 = 16 – starts after P4, P1 and P3;
Average waiting time: (3 + 16 + 9 + 0)/4 = 7
Operating System 2011/2012
14. Shortest-Job-First (SJF)
Suppose that the processes arrive in the order: P1 , P2 , P3, P4
with the respective computation time: 8, 4, 9, 3.
Waiting time for:
●
P4 = 0 – no process to wait;
●
P2 = 3 – starts after P4;
●
P3 = 9 – starts after P4 and P1;
●
P2 = 16 – starts after P4, P1 and P3;
Average waiting time: (3 + 16 + 9 + 0)/4 = 7
Operating System 2011/2012
15. Priority Scheduling
A priority number (integer) is associated with each process
●
The CPU is allocated to the process with the highest priority
(smallest integer – highest priority).
●
Can be preemptive (compares priority of process that has
arrived at the ready queue with priority of currently running
process) or nonpreemptive (put at the head of the ready
queue).
●
SJF is a priority scheduling where priority is the predicted
next CPU burst time.
●
Problem Starvation – low priority processes may never
execute.
●
Solution Aging – as time progresses increase the priority of
the process.
●
Operating System 2011/2012
17. 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.
●
Performance
●
q large -> FIFO
●
q small -> q must be large with respect to context switch,
otherwise overhead is too high.
●
Operating System 2011/2012
18. Multilevel Queue Scheduling
Ready queue is partitioned into separate queues:
➢
foreground (interactive)
➢
background (batch)
●
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, 20% to background in FCFS
●
Operating System 2011/2012
19. 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
Operating System 2011/2012
20. Multilevel Feedback Queue
Three queues:
●
Q0 – time quantum 8 milliseconds
●
Q1 – time quantum 16 milliseconds
●
Q2 – FCFS
Scheduling
●
A new job enters queue Q0 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 Q1.
●
At Q1 job is again served FCFS and receives 16 additional
milliseconds. If it still does not complete, it is preempted
and moved to queue Q2.
Operating System 2011/2012
22. Symmetric vs Asymmetric
Asymmetric: processors are dedicated to specific tasks.
Symmetric: processors can execute the same tasks and
exchange them during execution.
Operating System 2011/2012
23. Processor Affinity
Processor Affinity: the ability of a processor to exchange
process executing on run-time.
Soft affinity: a process can move from one CPU to another.
Hard affinity: a process can not move from one CPU to
another.
Operating System 2011/2012
24. Load Balancing
Push migration occurs when a specific task periodically
checks the load on each processor and move a process from a
busy CPU to an idle one.
Pull migration occurs when an idle processor pulls a waiting
task from a busy processor.
Operating System 2011/2012