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Questions tagged [threads]

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Thread wait state due to a cache miss

I know that a thread in a "running" state is put in a "wait" state if the thread itself needs I/O operation. Now I'm asking if even a cache miss implies that a thread is put in a &...
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2 votes
1 answer
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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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Why does python's threading library use OS level threads when it can't achieve parallelism?

I was surprised to hear that the threading module from python uses OS level threads. From what I know, OS level threads are more expensive (but can achieve parallelism) meanwhile green threads are ...
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1 answer
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Reader / writer locking algorithm

I'm pretty sure there's a textbook solution to this problem, but I haven't figured it out. I have fixed-size blocks of data arranged in a sequence: block 0, block 1, etc.. There are reader threads ...
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1 answer
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Deadlocks: Why if 2 threads are waiting for a lock from each other results in a deadlock?

I am confused as to why 2 threads waiting for a lock from each other will result in a deadlock. Let's say I have a Thread 1 that needs to execute contents in Lock 1 and then Lock 2 and a Thread 2 that ...
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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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0 votes
1 answer
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Which overhead is smaller - function call or passing variables between processes?

the question is related to networking frameworks; callback-based approach requires you to call a callback function every time you receive a new data packet; this is not a good approach for high-load ...
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2 answers
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What are the examples of multi-threading in a web server?

So I’ve been reading about multi-threading these past few days. Can you give me a real life example where the multi-threading might be used in a REST API web server?
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How do I call it when on Multi-threading I have a depency on a value that still doesn't exist?

On Multi-threading if I have multiple threads trying to access a single value I have a race condition. What is the name given if the condition is that I'm trying to ...
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  • 123
1 vote
3 answers
110 views

concurrency vs parallelism

I am so confused between concurrency vs parallelism in multi-core processors. If a concurrent process has many threads and if the processor is multi-core then can each thread run on multiple cores? If ...
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concurrency in multiple core

I know the basic definition between parallelism and concurrency. But there is not much information about concurrency in multiple core. what is the difference between concurrency in single-core vs ...
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1 answer
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Running an application that needs 6 threads on dual core processor

If a dual core processor have 4 threads, then what will happen if i run an application which uses more than 4 threads? And just to make sure i'm understanding what are threads in a cpu, when an ...
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Analyzing parallel performance question

I was reviewing for my CS class and came across this question and answer combo that didn't have any explanation why it was correct. I'm confused on how they got the answer: We have a system to which ...
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2 answers
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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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0 votes
1 answer
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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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5 votes
2 answers
471 views

Why do OS locks require hardware support?

I just read the chapter on locks in the book Operating Systems: Three Easy Pieces, and it discusses an implementation of locks (see in Figure 28.9) that involves a test-and-set hardware instruction. ...
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1 answer
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Why is it not a good idea to branch a thread outside of a parallel region while other threads are still executing?

Say I have $n$ threads executing in a parallel region and one of them leaves the parallel region when others are still continuing to execute in the parallel region. Why this is a $BAD$ idea? For ...
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1 vote
2 answers
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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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1 answer
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Does every thread have its main function?

Does every thread have its own main function? I know that its have its own stack, but what about main function (not necessarily a function which called main). For example, when creating a thread, we ...
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2 votes
1 answer
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What are the differences between Earliest Deadline First (EDF) and Earliest Due Date (EDD)?

From my understanding, the EDF (Earliest Deadline First) rule is essentially an iterative "version" of the EDD (Earliest Due Date) rule, which allows for preemption. At every point in time, ...
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Race Condition in Mesa Monitor

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1 answer
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How to trigger a thread to start working using semaphore?

How to trigger a thread to start working using semaphore? I have find a lot of explanation about thread and semaphore but i still don't understand, any help please
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Thread - contention vs race

The terms contention and race are used interchangeably when it comes to thread's state(at critical section). Are they same?
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0 answers
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parallelized data structure

I'm searching a data structure that supports O(1) concurrent insertions (thread number is known in advance) and iteration over its elements (insertion order doesn't need to be preserved). While one ...
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3 votes
2 answers
349 views

Why the most dominant programming languages didn't follow CSP thread model?

I was trying to ask this question in StackOverflow, but later realized that this question is more relevant to general computer science, not specific engineering problems. If you think it's not, please ...
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2 votes
1 answer
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How does a dual core microprocessors run so many programs?

I have a laptop with Intel dual core and it runs, the OS windows, and many application from Opera, age of empires, word, excel etc open at once just fine. If it only has 2 cores, how can so many ...
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0 votes
0 answers
103 views

Can many threads run in a parallel in many-to-one model?

The book I am reading suggests that in a many-to-one multi-threading model, the threads are unable to run in parallel in a multi-core system. I am thinking this is not the case because if we have many-...
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-2 votes
1 answer
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Does this lock have a name (related to reader-writer lock)

The object can be locked two different ways, where if the lock is entered the same way a second time, the lock is recursive, but if it's entered the other way, it blocks. Like a reader-writer lock, ...
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2 votes
0 answers
32 views

What does it mean by "consistent view of memory" in lock-free dequeue implementation?

I am currently reading this paper by Chales-Lev. This paper explain an implementation of work-stealing dequeue. The part where I don't understand is in the implementation of steal operation. ...
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1 vote
0 answers
26 views

Parallel Thread Processing Variable Question

if there is a better stack exchange suited for this question please inform me. say you have a thread that is constantly checking the state of a variable in 2 ms intervals ...
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0 votes
1 answer
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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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0 votes
1 answer
38 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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3 votes
1 answer
844 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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0 votes
2 answers
390 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 ...
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1 vote
1 answer
2k views

About hardware multithreading

I'm reading Multithreading (computer architecture) - Wiki, aka hardware threading, and I'm trying to understand the second paragraph: (p2): Where multiprocessing systems include multiple complete ...
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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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1 answer
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Reason for thread pooling

Can someone explain what is the reason for thread-pooling in Linux, even if the threads are light to create and destroy??
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1 vote
0 answers
31 views

Definition of PrefixSum function

I came across this paper and attempting to go through the implementation of randomized selection algorithm on page 8. Step 1 of the algorithm suggest to compute $s = PrefixSum(n_i, p)$. Where $p$ is ...
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1 vote
0 answers
25 views

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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0 votes
1 answer
52 views

Can Multiprocessor Systems Implement Both Temporal Multithreading and Simultaneous Multithreading?

I am aware that multiprocessor systems often implement simultaneous multithreading in order to allow multiple threads to run on different CPUs. I am also aware that uni-core systems often implement ...
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0 votes
1 answer
133 views

What is the Difference Between Many-to-Many (M:M) Threading and Hybrid (M:N) Threading?

I have been researching threading and come across several websites which all say contradicting statements about which and how many thread models exist. Some websites say there are only three: 1:1, M:1 ...
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1 vote
0 answers
57 views

semaphore for two groups of processes

Can someone help me giving a pseudo code to this problem : There are two groups of processes , A and B. Maximum 3 Processes from group A or group B(only from one group) can use the given resource . ...
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3 votes
1 answer
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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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1 vote
1 answer
250 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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1 vote
2 answers
434 views

What is the difference between a page and thread?

"Each process that is executed is divided into blocks of same size, called pages." "Thread is a part of process being executed." Are pages and threads both part(s) of process? Whats the difference ...
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1 vote
1 answer
160 views

Work-stealing: where and how many to steal

If one ignores the conflicts when accessing the dequeue in Work-Stealing algorithms, does it matter (and in what ways) if one steals from the top or bottom (or anywhere randomly) of the dequeue? Does ...
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1 vote
1 answer
24 views

Need to understand signals received vs sent

What is meant by in the following statement (from the paper titled "Implementing Lightweight Threads"): As in singlethreaded processes, the number of signals received by the process is less than ...
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0 votes
1 answer
274 views

Hardware thread context and register renaming

I'm having some issues understanding what happens on a context switch with the physical register file in an out-of-order CPU that implements context switching. Suppose that a CPU consists of 4 ...
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1 vote
1 answer
4k views

What is "time-slice multi-threading"?

My goal is to understand the exact differences between SoEMT, SMT and "time-slice multi threading". Thus far I already found information on SoEMT and SMT and it does not seem to hard to find more on ...
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  • 415
1 vote
1 answer
200 views

Multi-threading : N cores = N times one core?

This question is about modern CPU architectures and multi-threading. I'm mainly interested in personal computers or servers having 2, 4, 8, 16... cores like for example an Intel core i7. I mean not a ...
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