Questions tagged [operating-systems]

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

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1answer
6k views

Program compilation and execution flow

I was studying operating system concepts from Silberschatz, Galvin and Gagne's book (sixth edition) and I have some questions about the flow of execution of a program. A figure explains the processing ...
5
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1answer
373 views

What is the difference between a module in a monolithic kernel and a server in a microkernel?

I´m not exactly sure what kind of impact these two things have on kernel design. Are servers more flexible because of running in user space, for instance, and does adding a module require a new build ...
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2answers
253 views

What if the electricity goes off while a file is being renamed?

Suppose I'm renaming a file and the electricity goes off right in the middle. Naively, it looks like the file could be in some “half-renamed” state. Maybe the name would have half the old name and ...
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4answers
8k views

Is the 2nd parity bit in RAID 6 a simple calculation?

I'm trying to understand how the 2nd parity bit or byte is set in RAID 6. I'm reading a paper by H. Peter Anvin, and it goes into Galois field algebra, which is somewhat new to me. Anyway, a rep from ...
3
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3answers
4k views

How does worst-fit memory allocation react when encountering contiguous empty memory blocks?

So I have a problem understanding how the worst-fit protocol for memory allocation reacts to contiguous blocks of empty memory. None of the examples I have found address this possibility. For ...
6
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1answer
694 views

Variation of the dining philosophers: is the standard solution still valid?

I have a problem that is almost equal to the standard one of the dining philosophers, but has a quirk: while a philosopher thinks, he still holds the fork on his left. If after the period of thinking ...
7
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1answer
2k views

How are threads implemented in different OSs?

I was reading Linux Kernel Development by Robert Love, where I came across this Linux takes an interesting approach to thread support: It does not differentiate between threads and normal ...
2
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1answer
551 views

Massalin's Synthesis Quajects equivalent to ASM generating macros used in Game Oriented Assembly LISP?

Alexia Massalin's Dissertation on Synthesis was a Phd thesis on Operating Systems that contained a concept called 'Quajects' (see Chapter 4). This is some additional commentary on the Phd Thesis. ...
12
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1answer
5k views

Swap space management during pure demand paging

The following is a doubt that I came across while doing a OS home assignment - however, it seems more concept-based than a straightforward coding question, so IMHO I don't think the homework tag is ...
7
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1answer
254 views

What techniques exist for energy-efficient computing and networking?

I am currently reviewing the potentials of cloud computing regarding energy efficiency and green IT. In connection with this review I am having a look on techniques for increasing energy-efficiency in ...
9
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4answers
13k views

What is meant by interrupts in the context of operating systems?

I've decided to read Operating Systems Concepts by Silberschatz, Galvin Gagne (8th edition) over the summer. I've gotten to a topic that's confusing me - interrupts and their role as it relates to ...
4
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1answer
132 views

Requirements for emulation

What are the complete specifications that must be documented in order to ensure the correct execution of a particular program written in Java? For instance, if one were archiving a program for long-...
6
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1answer
2k views

How to interpret “Windows - Virtual Memory minimum too low” from a CS student point of view?

On my old 256MB RAM, pc I get this message. (I guess it is quite common) Windows - Virtual Memory minimum too low Your system is low on virtual memory. Windows is increasing the size of your ...
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7answers
2k views

What are examples of inconsistency and incompleteness in Unix/C?

In Richard Gabriel's famous essay The Rise of Worse is Better, he contrasts caricatured versions of the MIT/Stanford (Lisp) and New Jersey (C/Unix) design philosophies along the axes of simplicity, ...
7
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5answers
109k views

What is the average turnaround time?

For the following jobs: The average wait time would be using a FCFS algorithm: (6-6)+(7-2)+(11-5)+(17-5)+(14-1) -> 0+5+6+10+13 -> 34/5 = 7 (6.8) What would the average turnaround time be?
6
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2answers
9k views

Which queue does the long-term scheduler maintain?

There are different queues of processes (in an operating system): Job Queue: Each new process goes into the job queue. Processes in the job queue reside on mass storage and await the allocation of ...
57
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2answers
24k views

What happens to the cache contents on a context switch?

In a multicore processor, what happens to the contents of a core's cache (say L1) when a context switch occurs on that cache? Is the behaviour dependent on the architecture or is it a general ...
13
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1answer
5k views

What is the purpose of M:N (Hybrid) threading?

In other words, what advantages does Hybrid threading have over 1:1 (kernel only) and N:1 (user only) threading? This is a follow-up to What is the difference between user-level threads and kernel-...
33
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2answers
44k views

What is the difference between user-level threads and kernel-level threads?

After reading several sources I'm still confused about user- and kernel-level threads. In particular: Threads can exist at both the user level and the kernel level What is the difference between ...
5
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1answer
63 views

Which instruction yields atomicity in this expression that makes the result 2?

I am reading about atomicity and came across the following scenario ...
13
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1answer
4k views

Are all system calls blocking?

I was reading an article that describes the switch between user-space and kernel-space that happens upon a system call. The article says An application expects the completion of the system call ...
11
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4answers
263 views

Why store self and parent links (. and ..) in a directory entry?

Consider an filesystem targeted at some embedded devices that does little more than store files in a hierarchical directory structure. This filesystem lacks many of the operations you may be used to ...
9
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2answers
1k views

Round-robin scheduling: allow listing a process multiple times?

In a round-robin scheduler, adding a process multiple times to the process list is a cheap way to give it higher priority. I wonder how practical an approach this might be. What benefit does it have ...
10
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1answer
1k views

Are two-level schedulers only useful to manage swapping?

Two-level scheduling is useful when a system is running more processes than fit in RAM: a lower-level scheduler switches between resident processes, and a higher-level scheduler swaps groups of ...
18
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3answers
2k views

Clever memory management with constant time operations?

Let's consider a memory segment (whose size can grow or shrink, like a file, when needed) on which you can perform two basic memory allocation operations involving fixed size blocks: allocation of ...
19
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4answers
2k views

Does cooperative scheduling suspend processes when they perform an I/O operation?

Many operating systems references say that with cooperative (as opposed to preemptive) multitasking, a process keeps the CPU until it explicitly voluntarily suspends itself. If a running process ...

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