997371991qqcom • 2020-09-29 14:53:04

There are five criteria for scheduling, they are CPU utilization, throughput, turn around time, waiting time and response time.

 

When the CPU utilization rate increases, the number of switching jobs will be less, because of the less switching times, the response time will increase.
Reducing the average turnaround time can be scheduled by the shortest job priority, but this will make the long-term job hungry, which will increase the maximum waiting time.
The increase of CPU utilization makes CPU intensive work run for a long time as much as possible (reduce the context switch caused by IO or other interrupts). The increase of IO device utilization depends on making the queued IO intensive work run immediately, but it will increase the overhead of context switching. PostVer 0

1720650158qqcom • 2020-09-29 17:31:32

In order to better evaluate the CPU performance,There are <strong>five</strong> details for Scheduling Criteria.(1)<strong>CPU utilization</strong> – keep the CPU as busy as possible(2)<strong>Throughput</strong> – # of processes that complete their execution per time unit(3)<strong>Turnaround time</strong> – amount of time to execute a particular process(4)<strong>Waiting time</strong> – amount of time a process has been waiting in the ready queue(5)<strong>Response time</strong> – amount of time it takes from when a request was submitted until the first response is produced, not output  (for time-sharing environment)

Optimization Criteria:Max CPU utilization,Max throughput,Min turnaround time ,Min waiting time ,Min response time

SJF:According to the execution time indicated in the job application in the job control block, the job with the shortest execution time is selected for priority scheduling.

FCFS:according to max

<strong>Conflict</strong>:As CPU utilization increases, the number of switch jobs will decrease and the response time will increase due to a reduction in switch time. Reducing the average turnaround time can be the shortest work priority, which will increase the maximum wait time. The increase in CPU usage makes CPl Uintensive work run for as long as possible (reducing context switching caused by IO or other iterations). The increase in IO device utilization depends on making the queued L0 intensive work run immediately, but this increases the overhead of context switching. PostVer 0

hokyeejaufoxmailcom • 2020-09-29 17:43:29

<ul>
<li>Describe the details of the scheduling criteria.
<ol>
<li><em>CPU utilization</em>: to keep the CPU as busy as possible. It should range from 40 per cent (for a lightly loaded system) to 90 per cent (for a heavily used system);</li>
<li><em>Throughput</em>: to show the number of processes that are completed per time unit;</li>
<li><em>Turnaround time</em>: to sum the periods spent waiting in the ready queue;</li>
<li><em>Response time</em>: to show the time from the submission of a request until the first response is produced.</li>
</ol>
</li>
<li>Why these criteria are chosen?
<ul>
<li>Basically, we need some standards or measurements to compare the performances of different CPU scheduling algorithms in various situations. Those substantial difference can give us a reference to determine which algorithm, in a specific case, is judged to be best;</li>
<li>Those differences are actually from the properties of the algorithms. Then the criteria aforementioned are commonly concluding the properties and suggested for comparing CPU scheduling algorithms, whereupon these criteria are chosen.</li>
</ul>
</li>
<li>Discuss the cases in which we choose a minimum or maximum criteria, or average criteria?
<ul>
<li>In minimizing the maximum response time to get good service among all users, we might need minimum criteria;</li>
<li>To boost  the CPU utilization, we might need maximum criteria;</li>
<li>To get a more stable processing speed, we might need average criteria.</li>
</ul>
</li>
<li>Discuss the cases in which criteria will conflict with each other.
<ul>
<li>These can list many cases like we expect to maximize CPU utilization but the maximum response time is 1 second.</li>
</ul>
</li>
</ul> PostVer 0

kagenzaclaudiengmailcom • 2020-09-30 10:29:43

Scheduling Criteria
•There are several different criteria to consider when trying to select the "best" scheduling algorithm for a particular situation and environment, including: ◦CPU utilization - Ideally the CPU would be busy 100% of the time, so as to waste 0 CPU cycles. On a real system CPU usage should range from 40% ( lightly loaded ) to 90% ( heavily loaded. )
◦Throughput - Number of processes completed per unit time. May range from 10 / second to 1 / hour depending on the specific processes.
◦Turnaround time - Time required for a particular process to complete, from submission time to completion. ( Wall clock time. )
◦Waiting time - How much time processes spend in the ready queue waiting their turn to get on the CPU. ◾( Load average - The average number of processes sitting in the ready queue waiting their turn to get into the CPU. Reported in 1-minute, 5-minute, and 15-minute averages by "uptime" and "who". )

◦Response time - The time taken in an interactive program from the issuance of a command to the commence of a response to that command.

•In general one wants to optimize the average value of a criteria ( Maximize CPU utilization and throughput, and minimize all the others. ) However some times one wants to do something different, such as to minimize the maximum response time.
•Sometimes it is most desirable to minimize the variance of a criteria than the actual value. I.e. users are more accepting of a consistent predictable system than an inconsistent one, even if it is a little bit slower.
PostVer 0

cfeshete97gmailcom • 2020-10-02 12:29:14

2018529627022_FESHETE CHARLES DE-GAULLE


Different CPU scheduling algorithms have different properties and choice of a particular algorithm depends on the various factors. Many criteria have been suggested for comparing CPU scheduling algorithms.

The criteria include the following:

CPU utilisation –
The main objective of any CPU scheduling algorithm is to keep the CPU as busy as possible. Theoretically CPU utilisation can range from 0 to 100 but in a real time system it varies from 40 to 90 percent depending on the load upon the system.
Throughout –
A measure of the work done by CPU is the number of processes being executed and completed per unit time. This is called throughput. The throughput may vary depending upon the length or duration of processes.
Turnaround time –
For a particular process, an important criteria is how long it takes to execute that process. The time elapsed from the time of submission of a process to the time of completion is known as turnaround time. Turn-around time is the sum of times spent waiting to get into memory, waiting in ready queue, executing in CPU and waiting for I/O.
Waiting time –
A scheduling algorithm does not affect the time required to complete the process once it starts execution. It only affects the waiting time of a process i.e. time spent by a process waiting in the ready queue.
Response time –
In an interactive system turn-around time is not the best criteria. A process may produce some output fairly early and continue computing new results while previous results are being output to user. Thus another criteria is the time taken from submission of process of request until the first response is produced. This measure is called response time.

There are many different criterias to check when considering the "best" scheduling algorithm, they are:

CPU Utilization
To make out the best use of CPU and not to waste any CPU cycle, CPU would be working most of the time(Ideally 100% of the time). Considering a real system, CPU usage should range from 40% (lightly loaded) to 90% (heavily loaded.)

Throughput
It is the total number of processes completed per unit time or rather say total amount of work done in a unit of time. This may range from 10/second to 1/hour depending on the specific processes.

Turnaround Time
It is the amount of time taken to execute a particular process, i.e. The interval from time of submission of the process to the time of completion of the process(Wall clock time).

Waiting Time
The sum of the periods spent waiting in the ready queue amount of time a process has been waiting in the ready queue to acquire get control on the CPU.

Load Average
It is the average number of processes residing in the ready queue waiting for their turn to get into the CPU.

Response Time
Amount of time it takes from when a request was submitted until the first response is produced. Remember, it is the time till the first response and not the completion of process execution(final response).

In general CPU utilization and Throughput are maximized and other factors are reduced for proper optimization.

Scheduling Algorithms
To decide which process to execute first and which process to execute last to achieve maximum CPU utilisation, computer scientists have defined some algorithms, they are:

First Come First Serve(FCFS) Scheduling
Shortest-Job-First(SJF) Scheduling
Priority Scheduling
Round Robin(RR) Scheduling
Multilevel Queue Scheduling
Multilevel Feedback Queue Scheduling

Types Of Scheduling Criteria Conflicts

(a) CPU utilization and response time: CPU utilization is increased if the overheads associated with context switching is minimized. The context switching overheads could be lowered by performing context switches infrequently. This could, however, result in increasing the response time for processes.
(b) Average turnaround time and maximum waiting time: Average turnaround time is minimized by executing the shortest tasks first. Such a scheduling policy could, however, starve long-running tasks and thereby increase their waiting time.
(c) I/O device utilization and CPU utilization: CPU utilization is maximized by running long-running CPU-bound tasks without performing context switches. I/O device utilization is maximized by scheduling I/O-bound jobs as soon as they become ready to run, thereby incurring the overheads of context switches. PostVer 0

653968106qqcom • 2020-10-02 16:29:37

2018329621008徐天然
Scheduling Criteria:
CPU utilization.
Throughput: The number of processes that are completed per time unit is called throughput.For long processes, this rate may be one process per hour; for short transactions, it may be 10 processes per second.
Turnaround time: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: Turnaround time is the sum of the periods spent waiting in the ready queue.
Response time: Response time is the time from the submission of a request until the first time it takes to start responding.

It is necessary to maximize CPU utilization and throughput while minimizing turnaround time, waiting time and response time. However, some of these factors are in conflict. For example, if you want to maximize the throughput, it is necessary to let short processes execute first, which will increase the waiting time and response time of long processes. In most cases, it is necessary to optimize the average value, but in some specific cases, only a part of the factors may be concerned.

Conflict:
a. CPU utilization and response time
CPU utilization depends on the frequency of process context switching to a certain extent. For example, if we adopt the FCFS scheduling scheme, the CPU utilization may be relatively large, but inevitably, the response time will increase (obviously, the process waiting time in this way will be very unsatisfactory).
b. Average turnaround time and maximum waiting time
In order to reduce the average turnaround time, priority should be given to tasks that require less time, and then the waiting time of a process with a long time will undoubtedly be lengthened.
c. I / O device utilization and CPU utilization
The improvement of CPU utilization needs to reduce the number of context switches, while the improvement of I / O device utilization requires that I / O devices can run as soon as they are ready - this requires context switching, so the two are contradictory. PostVer 0

1730854984qqcom • 2020-10-02 17:01:32

Why these criteria are chosen?

Different CPU scheduling algorithms have different properties, and the choice of a particular algorithm may favor one class of processes over another. In choosing which algorithm to use in a particular situation, we must consider the properties of the various algorithms. Many criteria have been suggested for comparing CPU scheduling algorithms. Which characteristics are used for comparison can make a substantial difference in which algorithm is judged to be best. The criteria include the following:
<ol>
<li>CPU utilization: We want to keep the CPU as busy as possible.</li>
<li>Throughput: If the CPU is busy executing processes, then work is being done.</li>
<li>Turnaround time: From the point of view of a particular process, the important criterion is how long it takes to execute that process.</li>
<li>Waiting time: The CPU scheduling algorithm does not affect the amount of time during which a process executes or does I/O; it affects only the amount of time that a process spends waiting in the ready queue.</li>
<li>Response time: In an interactive system, turnaround time may not be the best criterion.</li>
</ol>
&nbsp;

Discuss the cases in which we choose minimum or maximum criteria, or average criteria? Discuss the cases in which criteria will conflict with each other.

&nbsp;

It is desirable to maximize CPU utilization and throughput and to minimize turnaround time, waiting time, and response time. In most cases, we optimize the average measure. However, under some circumstances, it is desirable to optimize the minimum or maximum values rather than the average. For example, to guarantee that all users get good service, we may want to minimize the maximum response time. PostVer 0

439731491qqcom • 2020-10-04 17:50:03

<strong>Q1: describe the details of scheduling criteria</strong>

<strong>Ans:</strong>

There are 5 scheduling criteria, as following:

1.CPU utilization -- range from 0 to 100 percent to keep the CPU as busy as possible;

2.Throughput -- the number of processes that are completed per time unit;

3.Turnaround time -- the interval from the time of submission of a process to the time of completion;

4.Waiting time -- the sum of the periods spent waiting in the ready queue;

5.Response time -- the time from the submission of a request until the first response is produced;

<strong>Q2: why these criteria are chosen?</strong>

<strong>Ans: </strong>

Different CPU-scheduling algorithms have different properties, and the choice of a particular algorithm may favor one class of processes over another. In choosing which algorithm to use in a particular situation, we must consider the properties of the various algorithms. Many criteria have been suggested for comparing CPU-scheduling algorithms. Which characteristics are used for comparison can make a substantial difference in which algorithm is judged to be best.

<strong>Q3: discuss the cases in which we choose minimum or maximum criteria, or average criteria?</strong>

<strong>Ans: </strong>

It is desirable to maximize CPU utilization and throughput and to minimize turnaround time, waiting time, and response time. In most cases, we optimize the average measure.

<strong>Q4: discuss the cases in which criteria will conflict with each other</strong>

<strong>Ans: </strong>

However, under some circumstances, we prefer to optimize the minimum or maximum values rather than the average. For example, to guarantee that all users get good service, we may want to minimize the maximum response time. PostVer 0

627864699qqcom • 2020-10-05 21:00:39

The details of scheduling criteria,
CPU utilisation : The main objective of any CPU scheduling algorithm is to keep the CPU as busy as possible. Theoretically CPU utilisation can range from 0 to 100 but in a real time system it varies from 40 to 90 percent depending on the load upon the system.
Throughout :A measure of the work done by CPU is the number of processes being executed and completed per unit time. This is called throughput. The throughput may vary depending upon the length or duration of processes.
Turnaround time : For a particular process, an important criteria is how long it takes to execute that process. The time elapsed from the time of submission of a process to the time of completion is known as turnaround time. Turn-around time is the sum of times spent waiting to get into memory, waiting in ready queue, executing in CPU and waiting for I/O.
Waiting time :A scheduling algorithm does not affect the time required to complete the process once it starts execution. It only affects the waiting time of a process i.e. time spent by a process waiting in the ready queue.
Response time : In an interactive system turn-around time is not the best criteria. A process may produce some output fairly early and continue computing new results while previous results are being output to user. Thus another criteria is the time taken from submission of process of request until the first response is produced. This measure is called response time.
WHY?
We need some standards to cpmare the performaances of different CPU scheduling algorithms and these criteria can show us.
When we disscuss the average criteria , it will show use the performance of this algorthm in most of the time. Bus the ave time will be affected by some very special circumstance.So we can discuss the maximum or minimum criteria. PostVer 0

1285795916qqcom • 2020-10-06 11:07:14

2018329621199 邱锐鹏

My answer of discussion 3 is in the following text file.

<a href="http://www.yvsou.com/wp-content/uploads/sites/30/2020/10/2018329621199_邱锐鹏_discussion_3.txt">2018329621199_邱锐鹏_discussion_3</a> PostVer 0

2470994471qqcom • 2020-10-06 14:53:25

the details of scheduling criteria  is as following

•CPU utilization. Conceptually, CPU utilization can range from 0 to 100 percent. In a real system, it should range from 40 percent (for a lightly loaded system) to 90 percent (for a heavily loaded system).

• Throughput. If the CPU is busy executing processes, then work is being done. One measure of work is the number of processes that are completed per time unit, called throughput. For long processes, this rate may be one process over several seconds; for short transactions, it may be tens of processes per second.
• Turnaround time. From the point of view of a particular process, the important criterion is how long it takes to execute that process. The interval from the time of submission of a process to the time of completion is the turnaround time. Turnaround time is the sum of the periods spent waiting in the ready queue, executing on the CPU, and doing I/O.
• Waiting time. The CPU-scheduling algorithm does not affect the amount of time during which a process executes or does I/O. It affects only the amount of time that a process spends waiting in the ready queue. Waiting time is the sum of the periods spent waiting in the ready queue.
• Response time. In an interactive system, turnaround time may not be the best criterion. Often, a process can produce some output fairly early and can continue computing new results while previous results are being output to the user. Thus, another measure is the time from the submission of a request until the first response is produced. This measure, called response time, is the time it takes to start responding, not the time it takes to output the response.

The reason of chosen those criteria: criteria are often defined in terms of CPU utilization, response time, or throughput. To select an algorithm, we must first define the relative importance of these elements.

&nbsp; PostVer 0

1403861656qqcom • 2020-10-06 22:32:39

the details of scheduling criteria：1.CPU utilization 2. throughput 3.turnaround time 4.waiting time 5. load average 6.response time

reason：

CPU Utilization

To make out the best use of CPU and not to waste any CPU cycle, CPU would be working most of the time(Ideally 100% of the time). Considering a real system, CPU usage should range from 40% (lightly loaded) to 90% (heavily loaded.)

Flux (Throughput)

It is the total number of processes completed per unit time or rather say total amount of work done in a unit of time. This may range from 10/second to 1/hour depending on the specific processes

(2) Turnaround Time

It is the amount of time taken to execute a particular process, i.e. The interval from time of submission of the process to the time of completion of the process(Wall clock time).

Waiting Time

The sum of the periods spent waiting in the ready queue amount of time a process has been waiting in the ready queue to acquire get control on the CPU.

Load Average

It is the average number of processes residing in the ready queue waiting for their turn to get into the CPU.
<h4>Response Time</h4>
Amount of time it takes from when a request was submitted until the first response is produced. Remember, it is the time till the first response and not the completion of process execution(final response).
<h4></h4> PostVer 0

512858048qqcom • 2020-10-07 15:52:36

<strong>1. The details of scheduling criteria include five aspects:</strong>
CPU utilisation: The main objective of any CPU scheduling algorithm is to keep the CPU as busy as possible. Theoretically CPU utilisation can range from 0 to 100 but in a real time system it varies from 40 to 90 percent depending on the load upon the system.
Throughput: A measure of the work done by CPU is the number of processes being executed and completed per unit time. This is called throughput. The throughput may vary depending upon the length or duration of processes.
Turnaround time: For a particular process, an important criteria is how long it takes to execute that process. The time elapsed from the time of submission of a process to the time of completion is known as turnaround time. Turn-around time is the sum of times spent waiting to get into memory, waiting in ready queue, executing in CPU and waiting for I/O.
Waiting time: A scheduling algorithm does not affect the time required to complete the process once it starts execution. It only affects the waiting time of a process i.e. time spent by a process waiting in the ready queue.
Respnse time: In an interactive system turn-around time is not the best criteria. A process may produce some output fairly early and continue computing new results while previous results are being output to user. Thus another criteria is the time taken from submission of process of request until the first response is produced. This measure is called response time.

<strong>2. The reason why these criteria are chosen:</strong> Because different systems have different functions, goals and metrics, different CPU scheduling algorithms have different properties and choice of a particular algorithm depends on the various factors.

<strong>3.</strong> It is desirable to maximize CPU utilization and throughput, and to minimize turnaround time, waiting time, and response time. In most cases, the average measure should be optimized.

<strong>4.</strong> For some systems such as time-sharing systems, it is more important to minimize the variance in the response time than it is to minimize the average response time. PostVer 0

454234624qqcom • 2020-10-10 20:10:54

<strong>1.Describe the details of scheduling criteria.</strong>

<strong>CPU utilization: </strong>keep the CPU as busy as possible. Conceptually, CPU utilization can range from 0 to 100 percent. In a real system. It should range from 40 percent (for a lightly loaded system) to 90 percent (for a heavily used system).

<strong>Throughput: </strong>the number of processes that are completed per time unit. For long processes, this rate may be one process per hour; for short transactions, it may be 10 processes per second.

<strong>Turnaround time: </strong>it is how long it takes to execute the process. The interval from the time of submission of a process to the time of completion is the turnaround time. Turnaround time is the sum of the periods spent waiting to get into the memory, waiting in the ready queue, executing on the CPU, and doing I/O.

<strong>Waiting time: </strong>is the sum of the periods spent waiting in the ready queue.

<strong>Response time: </strong>is the time from the submission of a request until the first response is produced. It is the time it takes to start responding, not the time it takes to output the response.

<strong>2.Why these criteria are chosen?</strong>

Because different CPU scheduling algorithms have different properties, and the choice of a particular algorithm may favor one class of processes over another. In choosing which algorithm to use in a particular situation, we must consider the properties of the various algorithms.

<strong>3.discuss the cases in which we choose minimum or maximum criteria, or average criteria?</strong>

It is desirable to maximize CPU utilization and throughput and to minimize the turnaround time, waiting time, and response time. In most cases, we optimize the average measure. However, under some circumstances, it is desirable to optimize the minimum or maximum values rather than the average. For example, to guarantee that all users get good service, we may want to minimize the maximum response time.

<strong>4.discuss the cases in which criteria will conflict with each other.</strong>

There are three cases as follows.

<strong>a.CPU utilization and response time:</strong> When frequent context switching is reduced to a minimum, CPU utilization increases. Reduce frequent context switching by reducing the use of context switching procedures. But this may lead to an increase in process response time.

<strong>b.Average turnaround time and maximum waiting time:</strong> The shortest average turnaround time can be minimized by executing the shortest task first. However, this scheduling strategy may make long-running tasks never scheduled and increase their waiting time.

<strong>c.I/O device utilization and CPU utilization:</strong> The maximum CPU utilization can be achieved by running CPU-limited tasks for a long time without context switching. The utilization of I/O equipment can be maximized by scheduling prepared I/O restricted tasks as much as possible. Therefore, it causes a context switch. PostVer 0

1210775967qqcom • 2020-10-12 21:12:03

<strong>Q1: describe the details of scheduling criteria. Why these criteria are chosen?</strong>
The criteria include thefollowing:
CPU utilization：keep the CPU as busy as possible.
Throughput：One measure of work is the number of processes that are completedper time unit.
Turnaround time：The intervalfrom the time of submission of a process to the time of completion is theturnaround tinne. Turnaround time is the sum of the periods spent waiting to get into memory, waiting in the ready queue, executing on the CPU, anddoing I/O.
Waiting time: The CPU scheduling algorithm does not affect the amountof time during which a process executes or does I/O; it affects only the·amount of time that a process spends waiting in the ready queue. Waiting time is the sum of the periods spent waiting in the ready queue.
Response time: In an interactive system, turnaround time may not bethe best criterion. Often, a process can produce some output fairly earlyand can continue computing new results while previous results are being output to the user: Thus, another measure is the time from the submissionof a request until the first response is produced. This measure, calledresponse tine, is the time it takes to start responding, not the time it takesto output the response. The turnaround time is generally limited by thespeed of the output device.

<strong>Q2: Discuss the cases in which we choose minimum or maximum criteria, or average criteria?</strong>
It is desirable to maximize CPU utilization and throughput and to minimize 1turnaround time, waiting time, and response time. In most cases, we optimizethe average measure. However, under some circumstances, it is desirableto optimize the minimum or maximum values rather than the average. Forexample, to guarantee that all users get good service, we may want to minimizethe maximum response time.

<strong>Q3: Discuss the cases in which criteria will conflict with each other.</strong>
For interactive systems (such as time-sharing systems), it is more important to minimize the variance in the responsetime than to minimize the average response time. A system with reasonableand predictable response time may be considered more desirable than a systemthat is faster on the average but is highly variable. However, little work hasbeen done on CPU-scheduling algorithms that minimize variance. PostVer 0

1119833189qqcom • 2020-10-13 14:42:41

(1) CPU utilization: need to make CPU as busy as possible. Conceptually, CPU utilization ranges from 0% to 100%. For real systems, it should be from 40% (light load system) to 90% (heavy load system).Throughput: If the CPU is busy executing a process, there is work being done. One method of measuring workload is called throughput, which refers to the number of processes completed in a unit of time. For long processes, throughput may be one process per hour; For short processes, the throughput might be 10 processes per second.(3) turnaround time: from the point of view of a particular process, an important criterion is to run the process needs how long.The time period from process submission to process completion is called turnaround time. The turnaround time is the sum of all time periods, including waiting to enter memory, waiting in the ready queue, executing on the CPU, and I/O execution.Wait time: CPU scheduling algorithm does not affect the process running and executing I/O time: it only affects the process in the ready queue waiting time. The wait time is the sum of the time spent waiting in the ready queue.(5) Response time: For interactive systems, turnaround time is not the best criterion. Usually, the process produces output fairly early, and the well continues to calculate the new result and outputs the previous result to the user. Therefore, the other time is from the time the request is submitted to the time the first response is generated. This time is called response time and is the time it takes to start the response, not the time it takes to output it. The turnaround time is usually limited by the speed of the output device.

Utilization and response time: CPU utilization increases when frequent context switching is minimized. throughReduce the use of context switches to reduce frequent context switches. However, this may result in an increase in process response time.Average turnaround time and maximum wait time: Average turnaround time can be minimized by performing the shortest tasks first.However, this scheduling policy may result in long-running tasks never being scheduled and increasing their waiting time. 0 device utilization and CPU utilization :CPU utilization can be maximized by running CPU-limited tasks for long periods of time without context switching. Maximizing 1/0 device utilization can be achieved by scheduling as many |/0 constrained tasks as are ready. Therefore, a. Context switch is caused PostVer 0

1079513613qqcom • 2020-10-13 15:16:13

Different CPU scheduling algorithms have different properties, and the choice of a particular algorithm may favor a class of processes. In choosing which algorithm to use in a particular situation, we must consider the properties of the various algorithms. Many criteria have been proposed for comparing CPU scheduling algorithms. Which features to compare can make a substantial difference in determining which algorithm is best. These criteria include:
CPU utilization: We want to keep the CPU as busy as possible.
Throughput: If the CPU is busy executing a process, the work is complete.
Turnaround time: From the perspective of a particular process, the important criterion is the time required to execute the process.
Wait time :CPU scheduling algorithm does not affect the amount of time during process execution or I/O; It only affects how long a process waits in the ready queue.
Response time: In an interactive system, turnaround time may not be the best standard.
Discuss the case where we choose the minimum or maximum criteria, or the average criteria? Discuss situations where guidelines conflict. We want to maximize CPU utilization and throughput and minimize turnaround time, wait time, and response time. In most cases, we optimize the average measurement. However, in some cases, we want to optimize the minimum or maximum, not the average. For example, in order to ensure good service for all users, we might want to minimize the maximum response time. PostVer 0

450766287qqcom • 2020-10-18 23:27:14

The criteria include the following:
CPU utilisation – The main objective of any CPU scheduling algorithm is to keep the CPU as busy as possible. Theoretically CPU utilisation can range from 0 to 100 but in a real time system it varies from 40 to 90 percent depending on the load upon the system.
Throughout – A measure of the work done by CPU is the number of processes being executed and completed per unit time. This is called throughput. The throughput may vary depending upon the length or duration of processes.
Turnaround time – For a particular process, an important criteria is how long it takes to execute that process. The time elapsed from the time of submission of a process to the time of completion is known as turnaround time. Turn-around time is the sum of times spent waiting to get into memory, waiting in ready queue, executing in CPU and waiting for I/O.
Waiting time – A scheduling algorithm does not affect the time required to complete the process once it starts execution. It only affects the waiting time of a process i.e. time spent by a process waiting in the ready queue.
Response time – In an interactive system turn-around time is not the best criteria. A process may produce some output fairly early and continue computing new results while previous results are being output to user. Thus another criteria is the time taken from submission of process of request until the first response is produced. This measure is called response time.
There are various CPU Scheduling algorithms such as-
First Come First Served (FCFS)
Shortest Job First (SJF)
Longest Job First (LJF)
Priority Scheduling
Round Robin (RR) PostVer 0

wx287_oz26ft1wt2_isbggtha4lgepaasa • 2020-10-27 14:35:23

1. The details of scheduling criteria include five aspects: CPU utilisation: The main objective of any CPU scheduling algorithm is to keep the CPU as busy as possible. Theoretically CPU utilisation can range from 0 to 100 but in a real time system it varies from 40 to 90 percent depending on the load upon the system. Throughput: A measure of the work done by CPU is the number of processes being executed and completed per unit time. This is called throughput. The throughput may vary depending upon the length or duration of processes. Turnaround time: For a particular process, an important criteria is how long it takes to execute that process. The time elapsed from the time of submission of a process to the time of completion is known as turnaround time. Turn-around time is the sum of times spent waiting to get into memory, waiting in ready queue, executing in CPU and waiting for I/O. Waiting time: A scheduling algorithm does not affect the time required to complete the process once it starts execution. It only affects the waiting time of a process i.e. time spent by a process waiting in the ready queue. Respnse time: In an interactive system turn-around time is not the best criteria. A process may produce some output fairly early and continue computing new results while previous results are being output to user. Thus another criteria is the time taken from submission of process of request until the first response is produced. This measure is called response time. 2. The reason why these criteria are chosen: Because different systems have different functions, goals and metrics, different CPU scheduling algorithms have different properties and choice of a particular algorithm depends on the various factors. 3. It is desirable to maximize CPU utilization and throughput, and to minimize turnaround time, waiting time, and response time. In most cases, the average measure should be optimized. 4. For some systems such as time-sharing systems, it is more important to minimize the variance in the response time than it is to minimize the average response time.

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2020-10-10 20:10:54 by 454234624qqcom

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1.Describe the details of scheduling criteria. CPU utilization: keep the CPU as busy as possible. Conceptually, CPU utilization can range from 0 to 100 percent. In a real system. It should range from 40 percent (for a lightly loaded system) to 90 percent (for a heavily used system). Throughput: the number of processes that are completed per time unit. For long processes, this rate may be one process per hour; for short transactions, it may be 10 processes per second. Turnaround time: it is how long it takes to execute the process. The interval from the time of submission of a process to the time of completion is the turnaround time. Turnaround time is the sum of the periods spent waiting to get into the 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. It is the time it takes to start responding, not the time it takes to output the response. 2.Why these criteria are chosen? Because different CPU scheduling algorithms have different properties, and the choice of a particular algorithm may favor one class of processes over another. In choosing which algorithm to use in a particular situation, we must consider the properties of the various algorithms. 3.discuss the cases in which we choose minimum or maximum criteria, or average criteria? It is desirable to maximize CPU utilization and throughput and to minimize the turnaround time, waiting time, and response time. In most cases, we optimize the average measure. However, under some circumstances, it is desirable to optimize the minimum or maximum values rather than the average. For example, to guarantee that all users get good service, we may want to minimize the maximum response time. 4.discuss the cases in which criteria will conflict with each other. There are three cases as follows. a.CPU utilization and response time: When frequent context switching is reduced to a minimum, CPU utilization increases. Reduce frequent context switching by reducing the use of context switching procedures. But this may lead to an increase in process response time. b.Average turnaround time and maximum waiting time: The shortest average turnaround time can be minimized by executing the shortest task first. However, this scheduling strategy may make long-running tasks never scheduled and increase their waiting time. c.I/O device utilization and CPU utilization: The maximum CPU utilization can be achieved by running CPU-limited tasks for a long time without context switching. The utilization of I/O equipment can be maximized by scheduling prepared I/O restricted tasks as much as possible. Therefore, it causes a context switch.

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2020-10-12 21:12:03 by 1210775967qqcom

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Q1: describe the details of scheduling criteria. Why these criteria are chosen? The criteria include thefollowing: CPU utilization：keep the CPU as busy as possible. Throughput：One measure of work is the number of processes that are completedper time unit. Turnaround time：The intervalfrom the time of submission of a process to the time of completion is theturnaround tinne. Turnaround time is the sum of the periods spent waiting to get into memory, waiting in the ready queue, executing on the CPU, anddoing I/O. Waiting time: The CPU scheduling algorithm does not affect the amountof time during which a process executes or does I/O; it affects only the·amount of time that a process spends waiting in the ready queue. Waiting time is the sum of the periods spent waiting in the ready queue. Response time: In an interactive system, turnaround time may not bethe best criterion. Often, a process can produce some output fairly earlyand can continue computing new results while previous results are being output to the user: Thus, another measure is the time from the submissionof a request until the first response is produced. This measure, calledresponse tine, is the time it takes to start responding, not the time it takesto output the response. The turnaround time is generally limited by thespeed of the output device. Q2: Discuss the cases in which we choose minimum or maximum criteria, or average criteria? It is desirable to maximize CPU utilization and throughput and to minimize 1turnaround time, waiting time, and response time. In most cases, we optimizethe average measure. However, under some circumstances, it is desirableto optimize the minimum or maximum values rather than the average. Forexample, to guarantee that all users get good service, we may want to minimizethe maximum response time. Q3: Discuss the cases in which criteria will conflict with each other. For interactive systems (such as time-sharing systems), it is more important to minimize the variance in the responsetime than to minimize the average response time. A system with reasonableand predictable response time may be considered more desirable than a systemthat is faster on the average but is highly variable. However, little work hasbeen done on CPU-scheduling algorithms that minimize variance.

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2020-10-13 14:42:41 by 郭丹婷

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(1) CPU utilization: need to make CPU as busy as possible. Conceptually, CPU utilization ranges from 0% to 100%. For real systems, it should be from 40% (light load system) to 90% (heavy load system).Throughput: If the CPU is busy executing a process, there is work being done. One method of measuring workload is called throughput, which refers to the number of processes completed in a unit of time. For long processes, throughput may be one process per hour; For short processes, the throughput might be 10 processes per second.(3) turnaround time: from the point of view of a particular process, an important criterion is to run the process needs how long.The time period from process submission to process completion is called turnaround time. The turnaround time is the sum of all time periods, including waiting to enter memory, waiting in the ready queue, executing on the CPU, and I/O execution.Wait time: CPU scheduling algorithm does not affect the process running and executing I/O time: it only affects the process in the ready queue waiting time. The wait time is the sum of the time spent waiting in the ready queue.(5) Response time: For interactive systems, turnaround time is not the best criterion. Usually, the process produces output fairly early, and the well continues to calculate the new result and outputs the previous result to the user. Therefore, the other time is from the time the request is submitted to the time the first response is generated. This time is called response time and is the time it takes to start the response, not the time it takes to output it. The turnaround time is usually limited by the speed of the output device. Utilization and response time: CPU utilization increases when frequent context switching is minimized. throughReduce the use of context switches to reduce frequent context switches. However, this may result in an increase in process response time.Average turnaround time and maximum wait time: Average turnaround time can be minimized by performing the shortest tasks first.However, this scheduling policy may result in long-running tasks never being scheduled and increasing their waiting time. 0 device utilization and CPU utilization :CPU utilization can be maximized by running CPU-limited tasks for long periods of time without context switching. Maximizing 1/0 device utilization can be achieved by scheduling as many |/0 constrained tasks as are ready. Therefore, a. Context switch is caused

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2020-10-13 15:16:13 by 1079513613qqcom

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Different CPU scheduling algorithms have different properties, and the choice of a particular algorithm may favor a class of processes. In choosing which algorithm to use in a particular situation, we must consider the properties of the various algorithms. Many criteria have been proposed for comparing CPU scheduling algorithms. Which features to compare can make a substantial difference in determining which algorithm is best. These criteria include: CPU utilization: We want to keep the CPU as busy as possible. Throughput: If the CPU is busy executing a process, the work is complete. Turnaround time: From the perspective of a particular process, the important criterion is the time required to execute the process. Wait time :CPU scheduling algorithm does not affect the amount of time during process execution or I/O; It only affects how long a process waits in the ready queue. Response time: In an interactive system, turnaround time may not be the best standard. Discuss the case where we choose the minimum or maximum criteria, or the average criteria? Discuss situations where guidelines conflict. We want to maximize CPU utilization and throughput and minimize turnaround time, wait time, and response time. In most cases, we optimize the average measurement. However, in some cases, we want to optimize the minimum or maximum, not the average. For example, in order to ensure good service for all users, we might want to minimize the maximum response time.

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2020-10-18 23:27:14 by 450766287qqcom

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The criteria include the following: CPU utilisation – The main objective of any CPU scheduling algorithm is to keep the CPU as busy as possible. Theoretically CPU utilisation can range from 0 to 100 but in a real time system it varies from 40 to 90 percent depending on the load upon the system. Throughout – A measure of the work done by CPU is the number of processes being executed and completed per unit time. This is called throughput. The throughput may vary depending upon the length or duration of processes. Turnaround time – For a particular process, an important criteria is how long it takes to execute that process. The time elapsed from the time of submission of a process to the time of completion is known as turnaround time. Turn-around time is the sum of times spent waiting to get into memory, waiting in ready queue, executing in CPU and waiting for I/O. Waiting time – A scheduling algorithm does not affect the time required to complete the process once it starts execution. It only affects the waiting time of a process i.e. time spent by a process waiting in the ready queue. Response time – In an interactive system turn-around time is not the best criteria. A process may produce some output fairly early and continue computing new results while previous results are being output to user. Thus another criteria is the time taken from submission of process of request until the first response is produced. This measure is called response time. There are various CPU Scheduling algorithms such as- First Come First Served (FCFS) Shortest Job First (SJF) Longest Job First (LJF) Priority Scheduling Round Robin (RR) PostVer 0

chipusilesgmailcom • 2020-11-17 14:15:48

Scheduling Criteria
<ul>
<li>There are several different criteria to consider when trying to select the "best" scheduling algorithm for a particular situation and environment, including:
<ul>
<li>CPU utilization - Ideally the CPU would be busy 100% of the time, so as to waste 0 CPU cycles. On a real system CPU usage should range from 40% (lightly loaded) to 90% (heavily loaded.)</li>
<li>Throughput - Number of processes completed per unit time. May range from 10 / second to 1 / hour depending on the specific processes.</li>
<li>Turnaround time - Time required for a particular process to complete, from submission time to completion. (Wall clock time.)</li>
<li>Waiting time - How much time processes spend in the ready queue waiting their turn to get on the CPU.
<ul>
<li>(Load average - The average number of processes sitting in the ready queue waiting their turn to get into the CPU. Reported in 1-minute, 5-minute, and 15-minute averages by "uptime" and "who".)</li>
</ul>
</li>
<li>Response time - The time taken in an interactive program from the issuance of a command to the <em>commence</em> of a response to that command.</li>
</ul>
</li>
<li>In general, one wants to optimize the average value of a criteria (Maximize CPU utilization and throughput, and minimize all the others.) However sometimes one wants to do something different, such as to minimize the maximum response time.</li>
<li>Sometimes it is most desirable to minimize the <em>variance</em> of a criteria than the actual value. I.e. users are more accepting of a consistent predictable system than an inconsistent one, even if it is a little bit slower.</li>
</ul>
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shatino94163com • 2020-12-22 14:38:29

Why these criteria are chosen? Different CPU scheduling algorithms have different properties, and the choice of a particular algorithm may favor one class of processes over another. In choosing which algorithm to use in a particular situation, we must consider the properties of the various algorithms. Many criteria have been suggested for comparing CPU scheduling algorithms. Which characteristics are used for comparison can make a substantial difference in which algorithm is judged to be best. The criteria include the following:
<ol>
<li>CPU utilization: We want to keep the CPU as busy as possible.</li>
<li>Throughput: If the CPU is busy executing processes, then work is being done.</li>
<li>Turnaround time: From the point of view of a particular process, the important criterion is how long it takes to execute that process.</li>
<li>Waiting time: The CPU scheduling algorithm does not affect the amount of time during which a process executes or does I/O; it affects only the amount of time that a process spends waiting in the ready queue.</li>
<li>Response time: In an interactive system, turnaround time may not be the best criterion.</li>
</ol>
Discuss the cases in which we choose minimum or maximum criteria, or average criteria? Discuss the cases in which criteria will conflict with each other.   It is desirable to maximize CPU utilization and throughput and to minimize turnaround time, waiting time, and response time. In most cases, we optimize the average measure. However, under some circumstances, it is desirable to optimize the minimum or maximum values rather than the average. For example, to guarantee that all users get good service, we may want to minimize the maximum response time. PostVer 0

1224532347qqcom • 2021-01-01 14:56:16

Before understanding the scheduling algorithm, we need to understand two very important concepts, which is helpful to understand the algorithm.

Deprivation mode: when a process is executing on the processor, the system can deprive the processor assigned to it according to the specified principles, and assign the processor to other processes. There are two common deprivation principles: high priority deprivation principle and time slice deprivation principle. In the former, high priority process or thread can deprive low priority process or thread of running, while in the latter, processor is deprived when running process runs out of time.

Non deprivation mode: once a process or thread starts to execute, it will not transfer the processor, unless the process or thread ends or an event occurs and cannot continue to execute.

The two strategies are generally used in combination: the kernel key program is non deprivation, and the user process is deprivation.

First come first service algorithm (FCFS)

Strategy: select jobs according to the sequence of jobs entering the system, and the jobs entering the system first will be selected. It is a non deprivation scheduling algorithm.

Effect: the algorithm is easy to implement, low efficiency, only focus on the waiting time of the job, do not consider the length of service time required by the job, not conducive to the short job and preferential to the long job. It is good for CPU busy jobs and bad for I / O busy jobs.

Linux adopts the first come first service algorithm and time slice rotation algorithm

SJF: shortest job first algorithm

Strategy: the shortest job first algorithm takes the CPU time required by the jobs entering the system as the standard, and always selects the jobs with the shortest estimated computing time to put into operation. It is a non deprivation scheduling algorithm.

Performance: the algorithm is easy to implement and inefficient. Its weakness is that it needs to know the CPU time required by the job in advance, but this time can only be estimated, and the estimated value is difficult to be accurate. If the estimation is too low, the system may terminate the job ahead of time. If the waiting time of the job is ignored, the hunger phenomenon will appear. Due to the lack of deprivation mechanism, it is not ideal for time-sharing and real-time processing.

The average job turnaround time of SJF is smaller than that of FCFS, so its scheduling performance is better than that of FCFS.

To realize SJF scheduling algorithm, we need to know the time required by the job, otherwise there is no basis for scheduling, and it is impossible to know the running time of a job accurately. PostVer 0

804824950qqcom • 2021-01-04 20:42:17

The criteria include the following:
CPU utilization, Throughput, Turnaround time, Waiting time, Response time.
Because these standards are direct factors that affect scheduling efficiency.
Minimum criteria: FCFS algorithm
MAximum criteria: Round robin algorithm
Average criteria: SJF algorithm
Conflict criteria: Preemptive priority scheduling algorithm
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2736689890qqcom • 2021-01-06 20:30:24

2018329621239--严宇豪CPU utilization Throughput Turnaround time Waiting time
Response time
CPU utilization will influence CPU calculation
throughput will influence process completed time
turnaround time will influence process and process completion time
waiting time will influencethe time of waiting in the queue
response time will influence the first time of response
we will max CPU utilization and min turnaround time waiting time. MOst time we will utilize average measure.
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2736689890qqcom • 2021-01-06 20:30:30

2018329621239--严宇豪CPU utilization Throughput Turnaround time Waiting time
Response time
CPU utilization will influence CPU calculation
throughput will influence process completed time
turnaround time will influence process and process completion time
waiting time will influencethe time of waiting in the queue
response time will influence the first time of response
we will max CPU utilization and min turnaround time waiting time. MOst time we will utilize average measure.
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