322-Exam2(Ch. 4,5)

What is a thread in the context of operating systems?

A fundamental unit of CPU utilization that forms the basis of multithreaded computer systems.

What is the difference between a process and a thread?

The unit of dispatching is a thread or lightweight process, whereas the unit of resource ownership is a process.

What does multithreading allow an operating system to do?

Support multiple, concurrent paths of execution within a single process.

What is the impact of using threads on application responsiveness?

Threads may allow continued execution of a process when part of the process is blocked, improving responsiveness.

What are the three primary thread libraries mentioned in the lecture?

POSIX Pthreads, Windows threads, and Java threads.

What is Amdahl's Law?

It identifies performance gains from adding additional cores to an application that has both serial and parallel components.

What is the many-to-one threading model?

Many user-level threads are mapped to a single kernel thread, which can cause blocking of all threads if one thread blocks.

What is a thread pool and what are its advantages?

A thread pool is a number of threads created to wait for work; it allows faster servicing of requests and better resource management.

In which scenarios are user-level threads (ULTs) advantageous?

ULTs provide faster thread switching without kernel mode privileges and can run on any OS.

What is the main disadvantage of User-Level Threads (ULTs)?

When it executes a blocking system call, all threads within the process are blocked.

What is the significance of thread-local storage (TLS)?

TLS allows each thread to have its own copy of data, making it useful in scenarios where the creation process is not controlled.

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

Kernel-level threads are managed and scheduled by the operating system, while user-level threads are managed by a user-level library.

What is the role of signaling in multi-threaded applications?

Signals notify a process of particular events; their delivery to threads can be controlled to ensure proper handling.

How does fork() behave in a multi-threaded environment?

In some UNIXes, it duplicates only the calling thread, which can lead to complications with local variables.

What is the main objective of CPU scheduling in multiprogrammed operating systems?

To introduce CPU scheduling which allows multiple processes to share the CPU resources efficiently.

What are CPU and I/O bursts in process execution?

A CPU burst is a period when a process is using the CPU, followed by an I/O burst where the process waits for I/O operations to complete.

In CPU scheduling, what is the role of the dispatcher?

Gives control of the CPU to the selected process, switching context and mode, and determining where to restart the program.

What is the First-Come-First-Served (FCFS) scheduling policy?

A non-preemptive scheduling policy where processes are scheduled in the order they arrive in the ready queue.

What does Shortest Job First (SJF) scheduling aim to achieve?

Select the process with the shortest expected processing time next to minimize average waiting time.

What are the two types of latency that affect real-time scheduling performance?

Interrupt latency is the time from the arrival of an interrupt to when it starts getting serviced, and dispatch latency is the time taken to switch the CPU from one process to another.

What is meant by 'aging' in priority scheduling?

Aging refers to the technique of increasing the priority of low-priority processes over time to prevent starvation.

How does the Round Robin (RR) scheduling algorithm operate?

Allocates a fixed time slice to each process; if it does not finish within that time, it is preempted and moved to the back of the ready queue.

What is the significance of time quantum in Round Robin scheduling?

Determines how long each process can run before it is preempted; it's crucial for balancing responsiveness and overhead.

What is the difference between Uniform Memory Access (UMA) and Non-Uniform Memory Access (NUMA)?

UMA provides equal memory access speed for all processors, while NUMA allows different access speeds for memory depending on the processor accessing it.