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Questions tagged [os-kernel]

Questions about the fundamental component of an operating system, which manages the allocation of resources to applications.

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What is the advantage of a hashed inverted page table versus an ordinary hashed page table?

A hashed inverted page table has a hash table that points each page number to its frame number. This frame number can then be used as an index to the inverted page table to get the PID and page number....
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Boot Loaders, Boot Sectors, BIOS, and GRUB

Again, I must apologize if this is "easily googlable". I have tried. My understanding is that the BIOS typically looks for the magic number 0x55aa at the end of a 512 byte sector (so bytes #...
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2 votes
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Are there any operating systems that utilize only user threads?

We're going over threading models in my freshman CS class. Are there any examples of operating systems that use exclusively user threads (N:1)? It looks like 1:1 is far and away the most common model ...
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What is the need for Kernel threads?

I'm a bit confused about kernel-threads, I searched a lot at the Internet, SOF and here but found very diverse and conflict answers. What is the need for Kernel threads? Are they threads that are only ...
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Over the course of history, did Linux and Windows NT kernel design learn from each other?

Linux Kernel in its primitive form was first written in 1991; Windows NT kernel (differ from Win9x Kernel which was based on DOS) purportedly began development in 1990. both being a monolithic kernel, ...
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How does the Linux kernel build its symbol lookup table?

I am writing a small x86-64 OS. I am trying to make sense of how Linux loads modules at runtime by linking them into the kernel. I understand that Linux builds a symbol lookup table. Basically, a ...
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What are the minimum functions, services, or features of a software to be called as an operating system?

When can we say that a software is an operating system and not a firmware, in terms of what it can do? I know that firmware is usually stored in ROM and OS is stored on HDD/SSD, but technically you ...
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LONG TERM SCHEDULER and how does it interact with USER

If I select chrome browser, then I select Android Studio, do they directly open in Ready Queue (allocated to RAM main memory), what processes actually goes into job queue? Does Job Queue gets filled ...
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What happens if there is context switch while executing system call?

Suppose a process does system call, hence it goes to kernel mode, the registers are saved. Now the system call will be running in process' allocated kernel stack. Can there be a context switch when a ...
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(reference) Where can I learn more about I/O operations in OS?

I have basic understanding of file I/O. I know how to operate the read and write system calls in Linux. I know that there is blocking and non-blocking I/O. I want to know more about the underlying ...
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What is meant by a single-threaded kernel?

I was looking at this course but I cannot seem to understand what is meant by the term "single-threaded kernel". Does it mean that: only a single kernel thread is made available by the OS? ...
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How are kernels (and operating systems in general) written in C?

I'm trying to understand how you set about writing an OS in something like C. I've always used C to write applications - using commands like malloc and ...
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How could i create a multi-threading system in a kernel?

Im trying to figure out if there's an assembler instructions or a bios intruction to get multi-threading in a kernel. In the case that doesn't exist that, how could i set muti-threading in a kernel?
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OS: Why is it necessary to have hardware support for implementing Preemptive Scheduling Strategies?

I think, Preemption can easily be done in kernel mode, where it just have to call the Context-Switch procedure. Also, based on algorithm we can select the new process from the ready queue as well... I'...
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Isn't a small monolithic kernel a micro-kernel, and a big micro-kernal a monolithic kernel?

I don't understand the last para. I corrected its typos. Please explain like I'm 5. If micro-kernels can be big, and monolithic kernels can be small, doesn't this size gradation collapse the ...
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OS: Are User-level threads and software threads (and also kernel-level threads and hardware threads) the same?

I am referencing the Book Fundamentals of Computer Algorithms" by Ellis Horowitz et al. At the part which they talk about multi-threading models, user-level and kernel-level thread are introduced....
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How were operating systems even made?

By that, I don't mean what is needed to make an operating system. I know that OSes are built on top of kernels and whatnot. But what I mean is, it wasn't like anyone could just "program" the ...
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Is vmlinux a virtual machine?

From Wikipedia, On Linux systems, vmlinux is a statically linked executable file that contains the Linux kernel Does that mean vmlinux is a virtual machine that runs Linux? I am really confused.
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Paging only for user code. What about kernel code?

Why is paging done only for user code (user space)? I know that the basic intuition behind paging is for managing larger logical address space in smaller physical main memory space. Won't the kernel ...
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1 vote
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Can User Level Thread read/write Kernel thread?

As far as I read in a OS text book (Operating Systems by Silberschatz) Kernel mode is for privileged task, so it it true to claim that "User Level Thread can read/write Kernel threads" ? ...
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Does FreeRTOS replace linux or run ontop? [closed]

I am looking into FreeRTOS, just for personal learning and I am stuck on how the fundamentals of how it works with Linux. So for example, I am able to build FreeRTOS on my linux ubuntu machine. Now ...
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Is it possible to run more than one Turing Machine emulator using only one processor kernel?

I had this question on computer architecture exam and can't find an answer anywhere. Is it possible to run several Turing Machine emulators at once using only one processor kernel? a) Yes, by ...
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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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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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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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A microkernel fully hardcoded in hardware?

Does there exist a (micro-)kernel of an operating system that is fully implemented in hardware? That is, a kernel that is not stored in RAM, and loaded into CPU registers after an interrupt or system ...
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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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Is it possible for a syscall to pack together different places in memory?

While programming with buffers like uint8_t* in C++ I often arrive at situations on where I'm forced to do copies. For example, if I receive packets in chuncks from ...
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2 votes
2 answers
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Why do operating systems freeze?

I am currently writing from a computer on which a VM has just frozen due to exhausted RAM. I am obviously no expert in the field of operating systems but i know that they implement certain memory ...
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How can the initial "booting" state of a computer be different at different time points? [closed]

In my experience, sometimes a computer boots normally, and in a time span of days, the computer won't boot, then again, it will boot normally again. I am not a computer science expert so I assume that ...
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How are hardware interrupts handled?

I have read that a hardware interrupt is handled asynchronously by the CPU, which means that the interrupt signal may arrive at any point of time with respect to the CPU clock cycle. Now, this means ...
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Why do we need volume as an abstraction on top of partition?

I'm curious about what do we need volume as an abstraction on top of hardware partition? What problem it tries to solve? What is the limitation of this concept?
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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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1 answer
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need for an example of synchronous but non periodic interrupt

I know that synchronous interrupts are interrupts that occur with a clock tick (after finishing an instruction) and I think that periodic if they happen in every n ticks of the clock. To get a better ...
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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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2 votes
1 answer
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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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User-level threads and information available to the kernel

User-level threads are transparent to the kernel. How is htop able to show user-level threads running on my system? I know that those threads are user-level threads ...
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13 votes
1 answer
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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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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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1 vote
1 answer
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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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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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Are Kernel Codes (which are written in C) compiled during boot time?

I have a confusion regarding how the Kernel is loaded during the boot time. The intuition I have is like following: During installation of an OS, the compiled Code of the Kernel (depending on the ...
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how applications send tcp data to internet?

What i know is that applications create "socket"(visualized concept for high level programmers),the socket will address the ip addresses and send to internet and forward the feedback data.What i ...
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On what abstraction is a filesystem actually built on?

Data is read in terms of a block from a storage device(magnetic, optical, flash). Size of the block depends upon the filesystem and os. The physical device may have different units of storage like ...
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6 votes
3 answers
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Why do we try to maximize Lagrangian in SVMs?

I was learning about support vector machines from MIT OpenCourseWare. I figured it out. I understand why we try to minimize $\frac{1}{2} w^2$. I just did not get why we try to maximize Lagrange ...
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1 vote
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Do user level threads take advantage of multi processing?

I asked this question here on stackoverflow, but maybe because of off-topic over there, it didn't received proper response. Does user level threads take advantage of multiprocessing ? I read one such ...
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Touchpad driver missing after windows 10 installation in acer E3-111-290X [closed]

I was asked by a friend to help installing windows 10 in an acer E3-111-290X that was previously running windows 7, but after installing windows 10 the touchpad stopped working.I've tried several ...
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9 votes
2 answers
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What is a file?

I'm looking for a formal definition of file that does not only include storage but also abstractions like procfs or /dev/null (or any fuse-based file) that do not relate to storage. So far I know ...
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4 votes
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Are these modern operating systems monolithic or microkernel?

I know that (at least at its conception) Linux and Mac OS were both monolithic kernels. My question is, what kind of kernels are Linux, Mac OS, and Windows today and why?
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How many bits are needed? Advantages/disatvantages of this configuration?

So the question is: Assume we had 15 CPU instructions and, for each instruction, we were trusting one particular component of the kernel to handle it. How many modes do we need to support (including ...
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