Questions tagged [operating-systems]

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

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244 views

Determining the linear address

So I am working on a question that requires me to find the linear address. Here's some information: Main memory size is 8GB, which translates to $2^{3} * 2^{30} = 2^{33}$. Block size is 16KB each, ...
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1answer
164 views

Mutual Exclusion by disabling interrupt

I am reading William Stallings operating system book which gives this pseudo-Code for disabling interrupt to achieve Mutual Exclusion ...
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1answer
385 views

Which Peterson’s Solution is right?

I have seen two different Peterson’s Solution to mutual exclusion, one is from Modern Operating Systems: ...
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2answers
60 views

Why does the operating system switch an active process to different cores?

When running a single-threaded application that is 'always busy', on a multi-core computer, modern operating systems will typically switch the process from one core to another from time to time. Even ...
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31 views

Are space allocated to C/C++ variables in secondary storage also in Compiled file?

Are data segments,heap,stack etc also present in secondary memory with compiled code then later mapped by OS to RAM when I open it?
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167 views

How can a user process even try to access a memory location its not allowed to when it doesn't have access to page table?

So is it even possible for a user process to even try to access a physical memory location that does not belong to it and therefore getting an error by operating system? because for example with a 32 ...
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344 views

How pictures and videos are usually loaded in Memory? [closed]

Lets assume I'm talking about Jpeg and Mp4 and a general video player(not sure if different ones load it differently, if they do please tell) So do video players (process) usually load the entire ...
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1answer
428 views

Can a safe state in Banker's Algorithm cause deadlock eventually?

I know that unsafe state does not always mean deadlock. That is a situation that banker's algorithm does not detect deadlock accurately. I am just wondering if there is any example of a safe state ...
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108 views

Page Replacement optimal verses MRU

A computer has twenty physical page frames which contain pages numbered 101 through 120. Now a program accesses the pages numbered 1, 2, …, 100 in that order, and repeats the access sequence THRICE. ...
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1answer
48 views

Fork() execution and number of processes

If a process executes the following code fork(); fork(); fork(); The total number of child processes created is given as 7 by a text book. But how does that ...
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32 views

Software and hardware communications [closed]

When you install an OS on a piece of hardware such as a Macbook, what is happening logically? In other words, how does the software "talk" to the hardware? Is it the same logical process with every OS ...
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296 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
779 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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4k 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
40 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 ...
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1answer
943 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
47 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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162 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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59 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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78 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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904 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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757 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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233 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
200 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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76 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?
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1answer
385 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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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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97 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
179 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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1k 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 ...
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1answer
103 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, ...
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168 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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825 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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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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92 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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170 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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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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84 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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111 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
11k 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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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
37 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
49 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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100 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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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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115 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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175 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'...