Questions tagged [operating-systems]
Questions about the principles of software that interfaces between hardware and applications.
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Multiprogramming within a paged system
So lets say that have a system with a PMMU that supports 10 bit
physical addresses, and its processes are only able to use 8 bit logical addresses. The page size is 64 byte and the word size is 1 byte....
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0answers
16 views
Persistent Memory Emulation Platform (PMEP) [on hold]
How can I access to Persistent Memory Emulation Platform (PMEP)? It is supposed to be designed by Intel to simulate Non-Volatile Memory. It's mentioned in a few articles but quite unclear how to get ...
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1answer
45 views
How does operating system display decimal numbers which are stored as binary? [duplicate]
What kind of magic happen with bytes in memory?
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1answer
41 views
Explain in laymen terms - How do modern programs translate into machine code
I'm sure this will benefit anyone else on a computer science fundamentals back-fill journey..
I'm slowly learning Assembly and while I'm starting to understand the core of it (MOV, JUMP, etc) and can ...
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0answers
52 views
Why does transaction-end block in a data journaling have to be atomic?
I am reading File Systems Journaling(http://pages.cs.wisc.edu/~remzi/OSTEP/file-journaling.pdf) from the textbook Operating Systems: Three Easy Pieces and I cannot understand the following: On page ...
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1answer
12 views
How the operating system allocated to dual-channels memory?
I learned that the boot loader transmit the operating system from Hard Disk to Main Memory during the booting process.
I wonder, today's computers are equipped with multiple slice of memory of dual-...
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46 views
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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0answers
21 views
Addresses with no memory allocated
I've read that a program can crash if it tries to access addresses with no memory allocated. But, how is it possible that an address has no memory allocated? When does it happen?
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0answers
15 views
Difference between present - absent bit and valid - invalid bit in a page table?
while reading I found this:
Present/Absent bit – Present or absent bit says whether a particular page you are looking for is present or absent. In case if it is not present, that is called Page ...
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0answers
22 views
Appreciating the concept behind file reading from terminals [migrated]
I am starting out in Operating Systems module and these question really caught me off-guard. These questions have no solutions.
(a) In Windows, start a command line shell, eg. cmd. Assuming that you ...
2
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1answer
50 views
Appreciation of the 5 state process model
I'm starting out in an Operating Systems module. I have a few understanding questions to think about, which will not be gone through in class.
A process state model is an abstraction (or model) which ...
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1answer
13 views
Memory Mapping Segment
I read that "Memory Mapping Segment"/"memory mapped file" is a segment of the virtual memory of a process, where a file or file-like Ressource is loaded into. It is for high performance file I/O.
I ...
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43 views
Two Process Solution for Critical Section Problem- Algorithm 1
I have started learning Critical Section Problem and its various solutions. To explain my question, let me first give a brief background of it.
The general structure for a two Process Solution for ...
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1answer
15 views
address spaces of changing processes
I read that the mapping for user-space processes is changed after each process switch. By mapping I mean the translation from virtual addresses to "real" memory address. I thought that processes are ...
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1answer
22 views
What does it mean " The outer level page table need not be page aligned?
The question is in context to multilevel page table. I was trying to solve numerical on multi-level paging and noticed that page size might not be same at all levels. I came across the point "Outer ...
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0answers
76 views
Difference between Response time, Execution time, and CPU time
I studied Computer Architecture from David A. Patterson and have came across the idea of Response time.
Response time also called Execution time. The total time required for the computer to ...
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1answer
14 views
multithreading - duration of jobs
" How long will it take for 2 jobs to complete if they're running in parallel, knowing that both have a total of 20 minutes of CPU usage time and 50% IO"
I calculated the CPU usage: ...
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0answers
10 views
Calculate for each block, the number of bytes that can be assigned to data and to pointers to other blocks
In trying to solve the following problem:
You are presented with the first 15 blocks of a secondary storage device (disk) which has a total of 30000 KB available. The linked allocation method is ...
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1answer
27 views
Threads and Operating System
In a computer, the processor executes different threads and changes between them, the operating system is a program at the end that it´s being executed by the processor, there exists the posibility ...
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0answers
19 views
If the string of N requests is repeated many times, which of the following is/are true?
If the string of N requests is repeated many times, which of the following is/are true?
I. The fewest page faults occur when M ≥ N.
II. LRU
(least-recently-used) and FIFO (first-in-first-out) will ...
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1answer
28 views
Round-Robin fashion exercise
In my Operating Systems class I have an exercise to sketch out how a round-robin algorithm would apply to a specific scenario, which is the following:
Now the correction that I was provided with by ...
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0answers
26 views
Definition of multiprogramming [duplicate]
Which combination of the following features will suffice to characterize an OS as a multi-programmed OS?
a. More than one program may be loaded into main memory at the same time for execution
b. If ...
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0answers
25 views
interrupts in operating system
Normally user programs are prevented from handling I/O directly by I/O instructions in them. For CPUs having explicit I/O
instructions, such I/O protection is ensured by having the I/O instruction ...
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1answer
24 views
ARM STM instruction: page fault problem with MMIO
The ARM STM instruction is described here in the ARM manual.
This instruction writes all or a subset of registers at memory locations starting from a base memory ...
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1answer
36 views
Instructing operating system - Knowing it's functionalities
TL;DR: I would like to know how a programming language, the OS and drivers work together to perform a task.
I (and we all) have used various softwares/modules/packages on the top of our OS which ...
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2answers
28 views
Who decides that process needs cpu time or not?
I wonder how does particular process gets CPU time or resources whenever it's
required to execute some instructions? When a process is in the idle state or waiting for input, it's not occupying the ...
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1answer
27 views
Is OS mode required for accessing general purpose registers
In which of the following cases a process executing in user model is required to enter into the OS mode?
(a) Decreasing the value of unsigned integer value in a register to less than 0
(b) Accessing ...
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1answer
37 views
What should be the minimum value when the two threads are executed concurrently
int count=0;
void *thfunc()
{
int ctr=0;
for(ctr=0;ctr<100;ctr++)
count++;
}
If *thfunc() is executed by two threads concurrently in a uniprocessor ...
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0answers
17 views
Relating L1 cache, TLB and main memory
Earlier while solving problems from computer organization book by Stallings, I came across the fact that
$T_a=(H_{L1})(T_{C1})+(1-H_{L1})(T_{C1}+T_M)$
where,
$T_a \rightarrow$ Average access ...
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0answers
16 views
How Does an Operating System/BIOS Determine Physical Addresses of Devices?
So I understand that in every computer, the Operating System, the BIOS, or both will determine the physical addresses of the hardware devices and then translate that into virtual addresses. What I don'...
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0answers
29 views
Deadlock vs “Progress” requirement of the solution to the critical section problem
I came across following problem:
Consider following code:
...
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1answer
35 views
Cache and Main Memory
As we know that average access time is given by
t=p*(tc)+(1-p)*(tc+tm)
where t represent the average time, p is the hit ratio , tc is the time to access the data from the cache and tm is time to ...
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0answers
28 views
How can I implement locking a range of values in a sorted sequence?
I am trying to write a general purpose locking algorithm which allows me to lock a range of contiguous values in a sorted array. To start with, these could be exclusive locks - so two concurrent locks ...
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0answers
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Number of memory cycles stolen for transferring one word
The storage area of a disk has the innermost diameter of 10 cm and outermost diameter of 20 cm. The maximum storage density of the disk is 1400 bits/cm. The disk rotates at a speed of 4200 RPM. The ...
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1answer
32 views
In a kernel, what are “global constructors”?
I am a beginner developing kernels (though I have developed several Hello World programs in C and C++). I frequently see reference being made to global constructors (e.g., osdev https://wiki.osdev.org/...
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2answers
60 views
Why are threads called the unit of dispatch?
Threads called the "unit of dispatch" but what does that mean? I was looking over the web and two operating systems books but I can't find the answer. It seems that processes are defined by two ...
2
votes
1answer
93 views
How does hashed inverted page table work?
I understand hash function and inverted page table, but then the book I read describes something called hashed inverted page table (use hash to accelerate the finding because IPT is large), with TLB ...
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0answers
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Why is it difficult to differentiate between system and user CPU time?
In the book, Computer Organization and Design, Fifth Edition, by D. Paterson, it is stated that
Differentiating between system and user CPU time is difficult to do
accurately, because it is often ...
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0answers
10 views
If the number of pages exceeds the number of frames, how can the process finish using Virtual Memory?
Mapping is not for paging, is it?
For instance if we have 12 pages and 8 frames. If 7 out of these 12 pages are loaded into the main memory, how can the process terminate?
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0answers
20 views
How is switching among user-level threads realised in the user space?
This is with respect to user-level threads where the kernel only knows about the process as a whole, and threads are created and maintained in the user space. Each thread has its PC, registers, stack ...
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0answers
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pool of free page frames OS
I read that in a paging scheme memory management, some os's have a paging daemon that wakes up periodically to inspect the memory of the RAM. This is to ensure that modified pages can be scheduled to ...
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1answer
20 views
How can we compute how many processes should be in memory at a time to make CPU utilization max?
From the given formula, we can compute the CPU utilization:
CPU Utilization = 1 - P^n
Where p is the probability of I/O and n is the total number of processes.
E.g, If we were to find CPU ...
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1answer
90 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
88 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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0answers
17 views
Longest Remaining Time first with Non-preemption
Below is a question from a quiz I attempted(for preparing for a competitive exam), I found the solution to be bit confusing and wanted to clear my concept.
Below was the solution given
I have a ...
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1answer
130 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
55 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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1answer
26 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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1answer
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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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1answer
275 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 ...
