Questions tagged [operating-systems]

Questions about the principles of software that interfaces between hardware and applications.

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1answer
21 views

Multi-processing cpu utilization estimate

I find a formula on my book to estimate cpu utilization under multi-processing. $ U = 1 - P^n $ U: cpu utilization P: cpu idle I want to know why or how to proof. Edit: The book is about ...
-1
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1answer
74 views

I have a question about resource alocation to avoid dead lock

In the code below, three processes are competing for six resources labeled A to F.How can I modify the get request in each procedure in this graph to avoid dead lock You cannot move requests ...
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2answers
7k views

Difference between dynamic loading and dynamic linking in the OS

First of all, I saw many answers of this topic in Quora, Stackoverflow, and this site. But, I couldn't definitely understand the difference between dynamic loading and dynamic linking. What I ...
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1answer
18 views

Are process-safe mutexes shared between OSes?

I understand you can use process wide mutexes, but does this still apply if you have an additional virtualized operating system provisioned? For example, take two OSes: ...
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1answer
19 views

Where are file-information like “created” or “last edited” actually stored?

I can access some information about the files ("created" or "last edited") on my PC. But where are those information actually stored? Are they stored by the operation system? Could be possible as if ...
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1answer
26 views

Why is there no one to many Multithreading Model?

I am studying various multi-threading models. Here the user threads are mapped to Kernel Threads. They are - ...
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1answer
41 views

What is the meaning of idiosyncratic when refering to multiprocess abstractions?

I am currently reading this paper on library operating systems, more specific on Graphene. I stumbled over the following sentence: "Because multiprocess abstractions, such as signals or System V IPC, ...
4
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1answer
77 views

Task scheduling algorithm that limits concurrency

My prof introduced us an algorithm with semaphores that was used to solve the "dining philosophers" problem. The algo is ok, apart from that it limits concurrency. What does mean that it "limits ...
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0answers
14 views

Operating Systems - Why Stack Growths For a Fixed Parameter N Are Inconsistent?

I am taking an Operating Systems course and as a project, we are printing the content of the PCB of a process from task_struct of that process and its mm_struct & vm_area_struct pointers. During ...
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0answers
91 views

Starvation algorithm in operating system

Is there an algorithm for mutual exclusion with shared flag variables, as the Peterson's one, that doesn't prevent the starvation ?
2
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1answer
112 views

Peterson algorithm for mutual exclusion

In the Peterson Algorithm for mutual exclusion an implicit assumption is that the operations with the shared global variables happen atomically. To me, this is not a superficial assumption , cause it'...
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1answer
92 views

Virtual Memory and processes

In a Operating System, who decides which parts of a program (or task) has to be stored in the virtual memory and which in the RAM ?
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0answers
43 views

Segmented Paging mechanism virtual and physical pages

I have a system which uses segmented paging. Every address is divided as follows: (s,p,d) = 2,2,11. Main memory has a capacity of 32KB. There are 4 segments which have 4 virtual pages each. I have to ...
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1answer
398 views

Definitions of: virtual address space, page size

(I can't seem to find actual definitions of these terms anywhere, only hints and guesses). Is it fair to say, that: Virtual address space is the amount of bytes that can fit into RAM cells of all ...
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1answer
407 views

Difference between Time-sharing computers and computers which use Round Robin scheduling algorithm?

So maybe I'm confused in these concepts but i thought that time sharing computer is a computer which the processor switches between different processes quickly to achieve a good response time but ...
3
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2answers
57 views

How does software detect if an interrupt has occurred if it cannot set it's own interrupt handlers?

I'm currently working on designing a relatively simple processor using a custom ISA . It will use interrupts for I/O . From what i know , once the interrupt controller issues an interrupt , the ...
0
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1answer
44 views

EDF vs Rate Monotonic context changes

I'm studying real time scheduling algorithms. In particular EDF and Rate monotonic. I have an intuition that using EDF we have less context changes than using Rate Monotonic. But i dont know how to ...
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0answers
264 views

Logical to Physical Address

I have an exam coming up and my teacher posted a practice exam for it. Problem is that I solved the question but I am not sure if I am doing it right or getting the right answer as he refuses to give ...
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0answers
120 views

Utilization Factor, periodic tasks and schedulability

We have 2 periodic tasks that start at the same moment in a monocore processor. Why can happen that, even if the utilization factor is <= 1, the 2 periodic tasks are not schedulable ? For example, ...
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0answers
21 views

Can we run a program without os? [duplicate]

Because os is a special kind of program so does that also mean a normal program can run without os ?
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1answer
62 views

Can an operating system without api still work? [closed]

In theory operating system is a special program run by itself without help so that also mean normal program can still run by itself mean that the need for api is not must have so finally can we have ...
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0answers
453 views

Latency and Throughput Bounds

Say that I have a superscalar processor and I am given the latency, issue and capacity (in clock cycles) for different instructions. What is the general formula for latency bound and throughput bound?...
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1answer
405 views

Why can't OSes swap out processes that are waiting for I/O?

In the book, Operating System Concepts, 9th Edition, there is this paragraph that I don't quite wrap my head around. Swapping is constrained by other factors as well. If we want to swap a process,...
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1answer
54 views

Are there any stochastic models of non determinism in the rate of program execution?

We know that typical operating systems and high level languages (especially those with garbage collection) cannot be used for real time operating systems. Java & jet engines don't mix, and ...
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0answers
114 views

bakery algorithm, switching up the condition

I'm currently studying the Bakery Algorithm. I understand it for what it is but now I want to switch it up a bit. If we changed the < in the 2nd ...
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1answer
69 views

what does the author mean by directory structure in operating system?

I'm reading Operating System Concepts by Avi Silberschatz(9thE), in section 11.4 File-System Mounting, the author explains the steps of filesystem mounting as follows: The operating system is ...
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1answer
205 views

What's the directory structure on disk that keeps the information of all files?

I'm reading Operating System Concepts by Avi Silberschatz(9thE), in chapter 11 File-System Interface, when the author explains the concepts of file, he states that The information about all files ...
5
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1answer
176 views

Is there any mechanism where the kernel portion of an OS in memory may also be swapped?

I'm recently learning the part of I/O buffering of operating system and according to the book I use, When a user process issues an I/O request, the OS assigns a buffer in the system portion of ...
0
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1answer
703 views

Bits of memory address used for page number?

A $64$-bit computer has a virtual mem space of $2^{64}$ bytes and the computer also uses memory paging with size of $2^7$ $(128)$ bytes. Work out the bits of the memory address which are used for ...
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2answers
48 views

Are Kernel Codes (which are written in C) compiled during boot time?

I have a confusion regarding how the Kernel is loaded during the boot time. The intuition I have is like following: During installation of an OS, the compiled Code of the Kernel (depending on the ...
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1answer
283 views

Context-switch between two processes

In response to a clock interrupt, the OS saves the PC and user stack pointer of the currently executing process, and transfers control to the kernel clock interrupt handler. Then the clock interrupt ...
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1answer
21 views

Need to understand signals received vs sent

What is meant by in the following statement (from the paper titled "Implementing Lightweight Threads"): As in singlethreaded processes, the number of signals received by the process is less than ...
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0answers
44 views

An energy consumption problem

We want to show one schedule of jobs consumes less energy than another one. For example, there are two schedules A and B. Both the schedules A and B schedule two jobs $j_1$ and $j_2$ with execution ...
1
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1answer
164 views

How to Identify which instructions are represented by this microcode

I'm having issues with a question how to identify which instruction are represented by this microcode. The pc starts at 5000 and 7000 and 7001 have values 31 and 64 - I'm really confused how to ...
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2answers
85 views

File systems and writing one

I am going through the following series of lectures on OS development . http://www.brokenthorn.com/Resources/ In the fourth tutorial , I came across the term " OEM" parameter block that stores the ...
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1answer
68 views

How does a buffer overrun corrupt the return address?

I got stuck on the following note while reading a paper about computer security: The stack mixes program data and control data – by overrunning buffers on the stack we can corrupt the return ...
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1answer
255 views

What does an “I/O Task” mean?

While reading an article, I noticed the use of term 'I/O Task': Indeed, suppose the currently running process is performing an I/O task (which, by definition, does not need the CPU to be ...
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1answer
51 views

How does the OS detect B&B violation from hardware?

After reading about Base & Bounds memory protection mechanism from Stanford CS140 lecture notes, I understood from the explanation below that there is an ...
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1answer
3k views

What does 'relocation' mean?

I am reading about Base & Bounds memory protection mechanism, and I noticed the use of the term 'relocation' in the context of ...
2
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1answer
259 views

Does starvation freedom imply progress?

The above answer taken from the book https://www.amazon.com/Operating-Systems-Sibsankar-Haldar/dp/8131730220 says starvation freedom may not imply progress as processes can be deadlocked. I think ...
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2answers
940 views

Does MMU contain and manage CPU caches?

I read about Virtual Memory in various CS references, however I'm still not sure whether CPU caches such as TLB, L1 and L2 are ...
3
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1answer
744 views

The meaning of 'Pool' in Computer Science

While reading about SIMD on Wikipedia, I noticed the use of the technical term Pool in the figure below: I didn't know what it ...
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1answer
313 views

Determine deadline for periodic task that enter ready queue in RTOS

I am currently trying to optimise the scheduler of FreeRTOS and in general Real-Time Operating Systems as a Project. In FreeRTOS, and I suspect other RTOS as well, we don't specify the deadline for ...
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3answers
2k views

What does “map” mean?

I have encountered the term many times, in various CS education materials: L2 CS162 (UC Berkeley): Memory-mapped I/O L4 CS162 (UC Berkeley): Memory mapped files L24 CS61 (UC Berkeley): “...
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1answer
88 views

What does 'buffering' mean?

I read the lecture 4 of CS162 (UC Berkeley: https://inst.eecs.berkeley.edu/~cs162/sp17/static/lectures/4.pdf), but I got little bit confused about the meaning of the keyword "buffered" they used when ...
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0answers
27 views

Deadlock necessary conditions [duplicate]

I read that the 4 conditions for deadlock prevention are necessary conditions and not sufficient. The four necessary conditions are :- Mutual exclusion. Hold and wait. No preemption. Circular wait. ...
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1answer
2k 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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1answer
7k views

Explain Hashed page tables in operating system

I have a difficult time understanding hashed page tables used in virtual memory management. Here is picture of the slide that I am referring to: I understand that p is hashed and then the hash is ...
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1answer
55 views

hardware interrupts and context switch

I have recently studied about interrupts and context switch i have read that the hardware interrupts cause the interrupt service subroutine to execute for this i read mixed articles saying that there ...
0
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1answer
368 views

Virtual Memory - Non-contiguous Memory Allocation

I'm studying for my operating systems final, and one question that my professor asked that I can't seem to find the answer to is the following: "Why does virtual memory use non-contiguous memory ...