Questions tagged [process-scheduling]

Questions about how operating systems decide which process to execute at which time.

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12
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3answers
26k views

What is the difference between Multiprogramming and Multitasking

I am finding it difficult to clearly differentiate between Multiprogramming and Multitasking. My primary source has been Wikipedia, but the WP article seems to be a little at odds with some less ...
4
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2answers
536 views

Paging: Does the page table of a process also gets swapped out when the process gets swapped out from main memory?

Does a process's page table too gets swapped out to secondary storage from main memory when the process gets swapped out to secondary storage from main memory? And gets swapped back in when the ...
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0answers
17 views

What is a job queue? [duplicate]

I have a hard time understanding the concept of job queue. For example, when a user clicks the icon of an executable, the newly created process is passed to a job queue, and the long term scheduler ...
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0answers
32 views

Is it okay to understand Job Queue Like this?

I have a hard time understanding the concept of job queue. Is it right if I understand job queue like the following??? For example, when user click the icon of an exe file, the newly created process ...
1
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1answer
23 views

Question about pointer in PCB structure and meaning of job queue

PCB structure exists inside kernel area. And in ready queue, which is Linked List, each Node of the queue is PCB. And this mean PCB Node has the next address of PCB in the queue, right?? Then My ...
7
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6answers
110k views

What is the average turnaround time?

For the following jobs: The average wait time would be using a FCFS algorithm: (6-6)+(7-2)+(11-5)+(17-5)+(14-1) -> 0+5+6+10+13 -> 34/5 = 7 (6.8) What would the average turnaround time be?
4
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2answers
662 views

Convoy effect in priority scheduling and SJF (Non preemptive)

In books, I have read that FCFS suffers from convoy effect. I think that even SJF and priority(both preemptive and non preemptive) can suffer from convoy effect. In SJF, if a process with large burst ...
2
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1answer
132 views

Algorithm favours CPU bound or I/O bound processes

Some scheduling algorithms favour CPU bound processes while others favour I/O bound processes. Which algorithm favours which type of process? My answers: SJF favours I/O bound processes.Explanation: ...
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0answers
18 views

How to place the deadlines in “Earliest deadline first scheduling” in this question?

So I followed this tutorial to get the concept of "Earliest deadline first scheduling". I have to implement this task >>> TASK. Now the thing which I am not getting in this Task is ...
0
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1answer
36 views

OS: Are User-level threads and software threads (and also kernel-level threads and hardware threads) the same?

I am referencing the Book Fundamentals of Computer Algorithms" by Ellis Horowitz et al. At the part which they talk about multi-threading models, user-level and kernel-level thread are introduced....
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1answer
198 views

Calculating minimum processing time for many recipes and tools

I originally asked this question on StackOverflow but a comment was made to the effect that my problem pertains to Job Shop Scheduling and that it was more of a comp sci problem than a programming ...
0
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1answer
173 views

Questions regarding CPU scheduling algorithms ( Round Robin and Priority scheduling )

Consider the following processes : 1) My First Question is if we need to schedule them using preemptive priority scheduling with Round-Robin for equal processes priorities with a quantum of 3. Here ...
0
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1answer
75 views

Cores, threads and sockets: what does it mean the calculation $T = tcs$ and the number on windows task manager performance?

Well, suppose then we have an CPU system such as: Thread(s) per core $\equiv t$ : 4 Core(s) per socket $\equiv c$: 4 Socket(s) $\equiv s$: 1 Then, we must to perform a simple ...
2
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5answers
2k views

Operating System - CPU scheduling Decisions

I understand that CPU scheduling takes place on 4 circumstances listed below: When the process changes state from Running to Ready Changes state from Running to Waiting Changes state from Waiting to ...
0
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2answers
621 views

Does throughput includes CPU idle time also?

I have 3 processes P1,P2,P3 having gantt chart as follows => Now, CPU remains idle in 0 - 2 sec and 44 - 47 seconds as I/O is taking place. Does, this affect throughput as 3 processes can be ...
0
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1answer
4k views

Operating Systems - SJN/Round Robin - turn around time + waiting time

2.(10 pts) a) You are given 4 processes in a batch system that all arrive at time 0 with the following CPU burst times: P1 : 35, P2: 25, P3: 13, P4: 22. Assuming there is no context switch ...
3
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2answers
3k views

What is a student process?

According to Galvin and Silberschatz, 5 queues are maintained in multilevel queue scheduling, each for: System Process Interactive Process Interactive Editing Process Batch process Student Process ...
2
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1answer
82 views

Early Deadline First (EDF) scheduling in real-time systems feasibility test proof

I am trying to prove Theorem 6.2 on page 127 of the book Real-Time Systems by Jane W. S. Liu: http://www.cse.hcmut.edu.vn/~thai/books/2000%20_%20Liu-%20Real%20Time%20Systems.pdf It is based on Early ...
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0answers
51 views

Gantt chart for Round Robin Scheduling using only arrival and completion time

I had the following question in my Operating System 'CPU- Scheduling' assignment- 4 processes A,B,C,D have estimated time of completion of 5,7,9,11 ns each. They are scheduled in a round-robin fashion ...
0
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1answer
51 views

Confused between the terms Process and Process Control Block

I was reading about the Long term scheduler, when I read that when memory is not enough and load on the CPU due to multiprogramming is too high, a process might be moved to secondary storage space (...
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1answer
137 views

Calculation of speed up of a program executed in multi-threaded system

Speed up of execution of a program is to be calculated within a multi-threading rather than a single thread system. The program's 30% instruction can be executed serially & rest can be executed ...
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0answers
26 views

Round robin doubt

Consider a system running ten I/O-bound tasks and one CPU-bound task. Assume that the I/O-bound tasks issue an I/O operation one for every millisecond of CPU computing and that each I/O operation ...
2
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1answer
3k views

User level threads are transparent to the kernel?

Find whether given statement True or False? Explain. User level threads are transparent to the kernel? My attempt : False. Since, user level threads are managed by a user level library however, they ...
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2answers
3k views

Peterson's vs. Bakery Algorithm

From my CS course, the Peterson's Algorithm and the Bakery Algorithm both are solutions which satisfy the 3 requirements of any solution to the critical section problem. a) What are their adv/disadv ...
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0answers
136 views

What are the differences between Earliest Deadline First (EDF) and Earliest Due Date (EDD)?

From my understanding, the EDF (Earliest Deadline First) rule is essentially an iterative "version" of the EDD (Earliest Due Date) rule, which allows for preemption. At every point in time, ...
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0answers
12 views

Why does Fully Utilized Thread Change over time?

While I was running a simple program which needed to run for a couple minutes, I made an observation I can't find an answer for on google. Here is a snip of my system monitor which demonstrates my ...
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0answers
19 views

Understanding proofs Lemma 11 & 10 in this specific Computer Science Scheduling Paper

I'm having a hard time wrapping my head around the proofs Lemma 11 and Lemma 10 (Pages 10 and 11) in this paper called: Preemptive and Non-Preemptive Real-Time UniProcessor Scheduling. Generally the ...
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1answer
100 views

Polynomial-Time reduction from Partition to MakeSpan

Partition Problem: Input: $A:=$ {$a_{1}, ..., a_{n} $}. $a_{i} \in \mathbb{N}$ $\forall i \in$ $\{1, \ldots, n\}$. Question: Exists a subset $A_{1} \subset A$ with: $\sum_{a_{i} \in A_{1}} a_{i} = \...
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0answers
20 views

Finding the timestamps of processes implementing Lamport's clocks

I have been asked this question, but don't know how to go about answering it. Three process, which are implementing Lamport's clocks, are running and a lot of events are taking, place including some ...
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1answer
127 views

Scheduling of process manufacturing with setup times

Overview The process manufacturing is (in contrast to discrete manufacturing) focused on the production of continuous goods such as oil. The planning is typically solvable by means of Linear ...
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0answers
29 views

How to compute this CPU scheduling exercise?

How can I compute this type of problem? My doubts are one the number of jobs, I have tried drawing a Gantt chart, but it becomes huge and unmanageable. How am I supposed to represent the results? ...
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0answers
20 views

Preemptive priority scheduling problem with same priority

So if T1(priority 3, arrived first) was preempted it is put back to the runqueue. If there is already T4(priority 3, arrived fourth) inside the runqueue, which one of these two will be handled first?! ...
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0answers
16 views

In completely fair scheduler in Linux, how to calculate the initial virtual run time of a process

I am trying to implement a completely fair scheduler. I want to know how to calculate the initial value of virtual run time of a process in order to insert the process into a red black tree
2
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1answer
126 views

What is cold-start penalty ? What are some ways to reduce it?

when a new process is created using a fork() function, there is a cold start penalty, what is this and why does it happen?
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2answers
9k views

How does the OS determine the CPU burst time of a process?

This question is related to OS. After having solved many problems in CPU scheduling I was wondering how does the CPU know the burst time of all the processes in the main memory before executing them? ...
0
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2answers
376 views

Round Robin Scheduling: No process in Ready Queue

First post here, glad I found this exchange. I am in my Operating Systems course at university learning process scheduling. In my homework assignment we have to fill out a simulated scheduling chart ...
0
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1answer
32 views

Round Robin time slice(quantum time)

In all books about this topic, I read that there is a rule of thumb is that 80% of the process execution time is lower than time slice. But how do I calculate this value? I looked at every article ...
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2answers
136 views

Does pre-emption of a process occur when that process is busy waiting?

I was reading about Peterson's Solution for Synchronisation. Let's assume the two shared variables to be int bool flag[2] and ...
2
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1answer
36 views

How does a dual core microprocessors run so many programs?

I have a laptop with Intel dual core and it runs, the OS windows, and many application from Opera, age of empires, word, excel etc open at once just fine. If it only has 2 cores, how can so many ...
0
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1answer
36 views

When does a semaphore issue a wait and when does it issue a signal?

In my textbook, Operating Systems: Internals and Design Principles (9th Edition) by William Stallings in chapter 5, it explains how semaphores work: The fundamental principle is this: Two or more ...
2
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2answers
3k views

Does a context switch happen when a process has terminated?

I know this might sound like a newbie question but let's say we have a priority based scheduling algorithm (non-preemptive) where all processes arrive at time 0 and based on priority the order is P1, ...
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0answers
91 views

Expected value of next CPU burst using exponential averaging

The burst time is needed for Shortest Job First (SJF) and Shortest Run Time First (SRTF) scheduling. To get the approximate burst time, we use the equation $$\tau_{n + 1} = t_n + (1 - \alpha)\tau_n$$ ...
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1answer
53 views

What is Round Robin's behavior when a process comes at the same time that the old process is swapped out?

Let's say there are two processes: p1 and p2, their arrival time and service time are 0,2 and 3,1 respectively. The time quantum is 2s. After excuting for two seconds, will the processor excute p2 ...
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1answer
2k views

Arrival Time vs Burst Time vs Priority Time? If Priority Time is the same, which process dispatch first?

The question is based on if we have the same Priority value when we are given: Arrival Time = AT, Priority and Burst Time=BT. 1.Say if we a table with AT, Priority and BT. To dispatch a process it is ...
3
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2answers
2k views

Scheduling algorithms and quantum time

I would like to know what impacts does a scheduling algorithm, let's say Round Robin or FIFO, have on an Operating System. I understand that a scheduling algorithm has the processes run in burst then ...
2
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1answer
426 views

How exactly does a CPU do process scheduling?

I know in theory how various scheduling algorithms work, such as round robin, where each process is given small time slices to run a few instructions, before the operating system passes execution onto ...
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0answers
31 views

What approach to solve an open shop problem with following constraints

Say we have an open shop scheduling problem with following constraints : No wait-time between operations of a job Multiple job types (meaning each job type has different set of operations eventhough ...
1
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1answer
208 views

Can a schedule be conflict serializable but not serializable?

A schedule is called conflict serializable if it can be transformed into a serial schedule by swapping non-conflicting operations. Then, My question is: Can a schedule be conflict serializable but ...
2
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1answer
985 views

Appreciation of the 5 state process model

I'm starting out in an Operating Systems module. I have a few understanding questions to think about, which will not be gone through in class. A process state model is an abstraction (or model) which ...
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0answers
3k views

Difference between Response time, Execution time, and CPU time

I studied Computer Architecture from David A. Patterson and have came across the idea of Response time. Response time also called Execution time. The total time required for the computer to ...