Questions tagged [operating-systems]

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

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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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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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Operating systems

how to find the turn around time in SJF without arrival time. I got a quiz it only contains the brust time. They ask to find the average turn around time. how I find it?
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Spin-Lock and Busy-Wait

This question has been asked and the top answer https://stackoverflow.com/a/38173155/12862537 is not satisfactory. So, it would be nice if someone could specifically point out the similarities and ...
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Not able to change computer date [closed]

I am using Ubuntu on my computer and the date is Feb 2018. If I try to change the date using date command, my PC reboots and after reboot, date is same.. I reinstalled the os but it's the same issue. ...
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Android apps IPC during navigation of activity

During navigation of activities in an Android app by clicking back button, the current activity is paused, the previous one is restarted and resumed and the former is stopped. How does activity ...
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Can a TLB hit lead to a page fault?

$Can$ $a$ $TLB$ $hit$ $lead$ $to$ $a$ $page$ $fault?$ My answer is yes, as say even after a TLB hit if the page in the memory is dirty and it will lead to Page fault. Other case can be that, it is ...
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Message passing inter process communication

I was reading a book on OS by Galvin. I well understood that blocking send will wait until it has loaded the message into the kernel buffer. In contrast, the non-blocking send system call will return ...
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How are Operating systems involved in execution of programs?

By my understanding, operating system is the abstraction layer above hardware. Which means that an operating system that supports two different CPU architectures can run the same code. But I still ...
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81 views

How many segments a process can have in operating system employing Segmentation for memory management

Some facts about "Segmented Paging" 1) Each process has one segment table. 2) There is one-page table per segment. Fact about "Paged segmentation" 3) Contains page table of segment table. Now ...
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Another feasible way to implement multi-level page table?

The advantage of a multi-level page table is that we can swap the inner-level page tables to some secondary storage. If however we want quick access to the whole address space, we have to keep all ...
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Is this a deadlock?

Consider we have two processes P1 and P2. There are also two semaphores M and N which are initialized to zero. Here's how they execute: ...
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What is the maximum directly adddressable memory capacity?

This is taken from OPERATING SYSTEMS: INTERNALS AND DESIGN PRINCIPLES by WILLIAM STALLINGS Consider a 32-bit microprocessor composed of 2 fields: the first byte contains the opcode and remainder an ...
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what is the difference between an adapter and a controller?

1- why do have a USB controller but a display adapter ? 2- I have heard the terms network adapter and network controller being used, is there a differance between those ?
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working set bits in working set approximation

I am looking at the example pdf from Cornell found here: https://www.cs.cornell.edu/courses/cs4410/2016su/slides/lecture13.pdf Also reading OS Concepts 10e Chapter 10 but it does not go into detail. ...
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1answer
39 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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1answer
61 views

Converting physical address to logical

In 8-bit address space there are 16 pages and the page table stores: 68792EA51BD3CF04 (hex) The physical address is 39h, what is the corresponding logical address? I have literally no idea what to ...
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Operating System scheduling

I was reading a book on Operating System by Galvin and came across this : In the latest version of Solaris, scheduling is controlled by loadable tables. Depending on the table currently loaded, the ...
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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? ...
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300 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 ...
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Can the same machine word sometimes be data and sometimes be code?

I have a question about machine words. We have data and a code segment in the memory which is addressed. If we take a word from it and let's say it is a code (instruction), and another one is some ...
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1answer
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Is “capability-based security” vs “hierarchical-protection-domain based security” a false dichotomy?

The wikipedia page on capability-based security states: Capability-based security is to be contrasted with an approach that uses hierarchical protection domains. However, in order to implement ...
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Does Dekkers solutions to critical section problem ensure progress?

I was reading concurrency control section from Operating Systems book by William Stallings. In this book, he gives three attempts by Dekker to give solution to critical section problem: Attempt 1 <...
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Question about system calls

I had read about the various functionalities of system calls recently in one of my coursebooks and about how they are used to allocate memory for new processes. The book didn't specify whether it was ...
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Hardware protection needed for operating system kernel

I have a question related to the hardware protection needed to implement an operating system kernel: Identify at least three hardware level mechanisms that are necessary to protect an operating ...
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Process scheduling arrival time FIFO

I am a CS student and for the exam(Operating System) I have a problem like this: I receive a list of 9 process, and for every process I receive execution time(burst) and waiting time(for FIFO/FCFS ...
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What does this mean: “The compile-time and load-time address-binding methods generate identical logical and physical addresses”?

I read this in my Operating System textbook. Does it mean that the logical addresses generated by compile-time binding scheme are the same as the logical addresses generated by load-time binding? Or ...
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1answer
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Operating System code suffers more cache misses than user code

I was going through the text of the book Computer Architecture: A Quantitative Approach. It has a section in Chapter 5 where it discusses the fact that OS code undergoes more cache misses as compared ...
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Is logical address generated by CPU and MMU same if Physical and Virtual address space are same?

The system has same physical and virtual address space i.e. 32-bit. Are the logical address generated by CPU and address generated by MMU same?
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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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Why can't OS's keep audio and video recording in sync?

It seems every program that purports to record webcams fails to keep audio and video in sync. Moreover, there are probably man millenia being spent by people trying to correct for this during editing....
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How many registers does a computer *need*?

I read about Why does a processor have 32 registers?, and others. Currently I am messing around with an OS in JavaScript, and wondering how many registers -- or more specifically, how many temporary ...
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Why doesn't everyone use distributed operating systems?

As requested by a moderator, this question as been separated from my question about microkernel-based operating systems. In the 1980's, the team that developed C and Unix developed a distributed ...
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LRU vs FIFO page replacement

I am wondering if there is an instance where FIFO results in less page faults than LRU. For example: 2,6,5,7... In this string, if I have to complete it by ...
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Deadlock: can the processes know about deadlock occurrence

Deadlock can happen when two processes are waiting for resources held by each other. Here can the two processes know that they are waiting for each other to release resources?
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Why doesn't everyone use microkernel-based operating systems?

From what I have read on operating systems, the impression I have been receiving is that, for at least 30 years, "everybody has known" that microkernel-based operating systems are "better" than ...
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1answer
513 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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1answer
102 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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Is there a OSI model equivalent for describing the abstract layers present in performing a computation for an operating system?

In describing where a system vulnerability exists, I often find a need for a model that partitions a operating system and its components into abstraction layers. Similar to how the Open Systems ...
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Journey of a process from compilation to execution [closed]

I am reading operating system, and after reading some topics (Processes, Main Memory management) I got somewhat confused. I have knowledge about certain things but I am not able to combine and ...
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Deadlock in resource allocation graph

I am unsure if there is a deadlock in this particular graph. Not sure if P2 and R2 make a cycle. As well as P2 - R3 - P1 - R1 - P2. It seems there is a cycle, but not sure if there is a deadlock ...
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How can i draw a general resource graph which cannot be completely reduced but which is free from deadlock?

How can i draw a general resource graph which cannot be completely reduced but which is free from deadlock? A general resource graph which can be completely reduced and hence is free from deadlock is ...
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Why do we need full-fledged workstations running massive OSes with massive software?

I've grown up with computers. While watching old computer TV programmes and documentaries and reading the news about constant issues with these modern systems -- everything from the sheer amount of ...
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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 ...
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Research papers related the Android OS's Adaptive Battery and Screen Brightness

I want to read the details of the Adaptive Battery Optimization and Adaptive Brightness techniques used in the Android operating systems as mentioned in this wired.co.uk article. I tried looking for ...
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External fragmentation of memory

Im trying to calculate the external fragmentation of a memory with the content UFFFUUFFUU where U is used, and F is free. Im confused as to how to do this, when i dont know the number that Used is ...
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How Are Segment Descriptors Used

I am following through James Molloy OS tutorials and I can't get my head around the GDT. I understand that it contains entries that describe segments, what I don't understand is,how are the segment ...
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3k 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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Doubt in effective memory access time in case of n level paging + TLB

I am getting confused with calculation of EEMAT(Effective memory access time). I decided to close the book and think on my own and make an equation. Please see whther this is correct or not. I thought ...
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how worst fit better than best fit?

I am a beginner. I have recently started studying OS. In textbook, it is written as best fit is worse than worst fit. Reason - external fragmentation. IMO,in case of variable partionioning, best ...

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