Questions tagged [process-scheduling]

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

34 questions with no upvoted or accepted answers
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Problems of cyclic executive approach for scheduling of real time systems

I have a doubt on the cyclic executive approach for scheduling on real time systems. From Alan Burns's book Real-time Systems and Programming Languages. This final property represents one of the ...
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1answer
571 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 ...
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2answers
401 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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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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107 views

long-lived scheduling using max-flow & push/relabel

I'm writing a scheduler of long-lived Processors which execute long-lived Tasks. Processors and Tasks may each come and go over time, at any time (when a Processor departs, its assigned Tasks now ...
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41 views

Identify common mathematical problem behind my task in scheduling area

Having single operator, which could do work and it's time of availability - for example from 8 am till 9 pm. And operator have limited resource - let's call it ...
2
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0answers
40 views

How can I talk about priority inversion if it's impossible to specify priority?

In the paper: Leslie Lamport: What It Means for a Concurrent Program to Satisfy a Specification: Why No One Has Specified Priority; ACM Symp Principles of Programming Languages, (POPL-12):78-83, ...
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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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68 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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29 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 ...
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2k 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 ...
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73 views

Appropriate algorithm or heuristic for task scheduling

I'm sure this problem has been addressed before, but I'm unable to find an exact description of it. I have $m$ machines, and $n$ tasks that need processing. Each task takes a variable amount of ...
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44 views

Scheduling identical jobs with Cmax/Ci

I have $x$ uniform machines that are identical, except that each runs at a different speed; machine $j$ runs at speed $s_j$. I have $n$ identical jobs. Each machine can handle one job at a time. ...
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107 views

Processes running in Distributed Systems (Advanced Operating System)

I had a test today, there was a question that was a bit confusing. Anyway I am asking the question, from memory, and explaining what I answered. It would be great if someone could explain if I did ...
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0answers
281 views

Optimality of EDF

For Earliest Deadline First, I have read that if utilization is less or equal to 1, the task set is schedulable under EDF. But does this criteria expresses the optimality for EDF? If not, how can we ...
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115 views

Processes concurrency

I am getting ready for my end of year exams and I got stuck on this question. Consider the following 3-process concurrent program which uses semaphores S1, ...
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34 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 ...
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20 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 ...
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63 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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1answer
26 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 ...
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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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28 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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1answer
92 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 ...
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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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15 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
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123 views

Advantages of Preemptive Scheduling

I'm currently studying for an exam which includes operating systems. I'm solving the exams from previous years and I'm stuck on a particular question: "One of the advantages of preemptive scheduling ...
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47 views

Process scheduling accounting for multiple factors

I'm attempting to solve a problem that consists of scheduling two types (A and B) of processes to run. The system must be non-preemptive (once a process starts executing it must finish before another ...
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1answer
106 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 ...
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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 ...
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157 views

Why TurnAround Time is considered as Performance Metric for Scheduling Algorithms?

I know what is turn around time but i am confused why wating time is not considred as Performance Metric for Scheduling Algorithms Since it gives the time for which a Process will wait till it gets ...
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497 views

why p1 misses it first deadline? Rate monotonic scheduling

I understand that rate monotonic scheduling assigns a priority to a process based on the periodicity of the tasks it generates and the process with the shortest inter-task period has the highest ...
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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 ...
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43 views

Average time for jobs in a batch processing system

I saw this question , I want to know if anyone can help me solve it. Four jobs arrive at a batch processing system at the same time and the excution for each job is 2 hours. They run on a a single ...
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1answer
101 views

OS process management

Assume a process execution interrupted at the middle and CPU started executing a different process.How does the OS handle this situation?