Questions tagged [operating-systems]

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

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1answer
243 views

Are multiple interrupts generated when I hold down a key on my keyboard?

When I hold down a key on my keyboard, a continuous stream of characters is generated and is displayed on the text editor, Now since pressing a key is a hardware interrupt, so does holding down a key ...
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1answer
582 views

Processor pipelining question: number of instructions per second

A question from the textbook Modern Operating Systems by A. S. Tanenbaum reads as follows: A computer has a pipeline with four stages. Each stage takes the same time to do its work, namely, 1 nsec. ...
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1answer
3k views

What is the real advantage of Google's new Fuchsia operating system kernel?

Google's new in-production OS which it desires to replace not only Android but many other devices utilizes a completely new kernel: The code differs from Android and Chrome OS due to its being ...
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1answer
39 views

What is the mathematical principle of buddy algorithm?

The buddy algorithm is: The buddy for any block of size $2^k$ is another block of the same size, and with the same page frame number except that the kth bit is ...
5
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1answer
832 views

What's the difference between user registers and kernel registers?

I am reading Operating Systems: Three Easy Pieces, but I can't fully understand the following paragraph. It's from the 6th chapter of the book. I think it's self-contained, so I quote here. Note ...
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1answer
45 views

Can a process run if there's not enough space for minimum pages?

I'm studying OS and I came up with this scenario where the OS works with a paging scheme and virtual memory, and a process wants to start running, but in memory, there's not enough space to allocate ...
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156 views

How is context switching disabled in a process?

By what provision is context switching disabled in a process ? Or is it the case that if a process is in in kernel mode , context switching is disabled by default ?
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1answer
43 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?
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1answer
75 views

why do we run out of heap space even if we have virtual memory?

Whenever we try to get space in heap(using malloc or new) we can get out of heap space error if it exceeds the limit. But, we have virtual memory so why can't OS allocate that much space and then do ...
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1answer
834 views

Peterson Algorithm for process synchronisation

Consider Peterson's algorithm for mutual exclusion between two concurrent processes i and j. The program executed by process is shown below. repeat ...
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1answer
711 views

What is hardware trap?

Since it's called a trap I consider it caused by software, so why it's called a hardware trap? And how does it work?
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20 views

Operating System: Redundancy of implement a monitor using semaphores in my textbook?

Why the part highlighted the following picture is need? I've been trying to follow to logic flow of it as follow: Imaging a Situation: Two processes enter/call F, first A, second B: Process A: <...
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0answers
224 views

Operating System: Busy waiting is not eliminated with semaphore?

Why the busy waiting is not eliminated even after we put the current process into the process list and "block()"ed it? So even if the process is in waiting state we still call it "busy waiting"? I'm ...
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1answer
194 views

Operating System: About user thread and kernel thread?

Is that a "thread" consists of both "user thread" and "kernel thread" as two parts? And when I create a "thread", is that I create a "user thread" and another "kernel thread" is created "in the ...
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1answer
61 views

Operating System: replace the process's memory space with a new program

What does it mean that "replace the process's memory space with a new program"? So who's memory space will be replaced by whom?
3
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1answer
326 views

How do modern Operating Systems detect process starvation?

So first off do the modern operating systems like windows and linux have a method for detecting starvation? if not, why? and if they do, then how are they going to detect starvation of a process? (...
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0answers
29 views

Why isn't a process's PCB present in its memory?

I checked wikipedia PCB and its written that - Since PCB contains the critical information for the process, it must be kept in an area of memory protected from normal user access. In some operating ...
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2answers
86 views

How is space from malloc allocated?

Whenever we load a process (which consists of object code, static and global variables, stack and heap space) into main memory it would be of fixed size. But, the program doesn't know in advance how ...
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3answers
166 views

Is it 100% OK to say “All software doesn't need to know the system lower than the architecture level”?

Most of you know this diagram. If this diagram is true, all software is free to not know the levels lower than ISA. But it's not true. Softwares like performance-critical programs or system softwares ...
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1answer
36 views

Linux OS/HW VM cooperation

From what i've learned, the HW is responsible for setting the accessed and dirty bits in the PTE of a process, and the OS is responsible for turning them off. My question is why? The first part, i ...
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1answer
986 views

How does the TLB identify a particular process?

I have read that the translation lookaside buffer (TLB) is implemented in hardware and stores the page numbers and the corresponding frame numbers for faster lookups. Now suppose there are two ...
3
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1answer
101 views

What is the benefit of using one to one thread mapping model instead of Many to Many or two level?

So in the silberschatz O.S book it says Windows uses one to one model (mapping user level threads to kernel level threads) but why? i thought many to many and two level models are much better, ...
4
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2answers
132 views

Why operating system needs interrupt stack, if it has process control block?

I'm reading about an operating system but some concept confuses me. What doesn't confuse me: When an interrupt or system call or processor exception occurs, it happens when user mode tries to ...
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1answer
768 views

What is the relation between Time Sharing operating systems and Round Robin CPU scheduler?

So i have asked this before, but i still didn't get my answer so I'll try to make my question more clear this time : Based on my O.S book, Time sharing operating systems switch between processes ...
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0answers
1k views

CPU scheduling Algorithm SJF VS SRTF average waiting time?

Let's say we have two CPU scheduling algorithm as SJF and SRTF and we have a arbitrary pool/set of processes with different ARRIVAL TIME and CPU BURST, then what CPU scheduling algorithm will result ...
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1answer
88 views

What are the recents topics of research that combine both systems research and theoretical computer science?

I am an undergraduate majoring in Computer Science and Mathematics. For my undergraduate research, I would like to work on something that lies in the overlap between systems research and theoretical ...
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1answer
164 views

NX Bit in x86 vs x86_64

I've been reading about how the kernel manages memory in x86 from this popular blog post(https://manybutfinite.com/post/how-the-kernel-manages-your-memory/) and had a few questions. There is a part ...
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1answer
33 views

How can segment be 60KB

I read that each segment is 64KB,but how? If you have address ABCD:EFGH , then 1 segment is 16B if it is addreses by bytes. How do they don't overlap? Example: 0000:0010 = 00010 0001:0000 = 00010 , ...
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1answer
76 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 ...
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1answer
110 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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3answers
10k 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
22 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
36 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
48 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, ...
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1answer
88 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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112 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 ?
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1answer
165 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
122 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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45 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
592 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
597 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 ...
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2answers
82 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 ...
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268 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
142 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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22 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
63 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
659 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
900 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,...