Threads

What defines a process?

• Assigned a unique address space.

• Granted I/O and file resources.

• Protected by the OS from interference by other processes.

What does multithreading enable in an OS?

• Supports multiple concurrent paths of execution within a single process.

• Allows parts of a program to execute in parallel.

What are the characteristics of a thread within a process?

• Has its own execution state, thread context, program counter, stack pointer, and frame.

• Shares the parent process's resources.

• Managed through a Thread Control Block (TCB).

What are the benefits of multithreading in applications?

• Enhances performance in PC and console games, database operations, and Java applications.

• Allows for the simultaneous execution of multiple tasks within an application.

How does thread creation and termination benefit system performance?

• Faster to create and terminate a thread compared to a process.

• Easier and quicker to switch between threads than between processes.

• Threads can communicate more efficiently than processes.

What are the main types of threads?

• User Level Threads (ULTs): Managed by the application, invisible to the kernel.

• Kernel Level Threads (KLTs): Managed by the kernel, allowing better multiprocessing and system utilization.

What are the advantages of User Level Threads (ULTs)?

• Do not require kernel mode privileges, allowing for application-specific scheduling.

• Compatible with any operating system.

What are the disadvantages of User Level Threads?

• A system call can block the entire process.

• Cannot be scheduled across multiple cores by the OS.

What are the advantages of Kernel Level Threads?

• Supports multiprocessing; other threads can run if one thread blocks.

• Kernel routines themselves can be multithreaded.

What does Amdahl’s Law state about multithreading performance?

• More threads speed up a program only when many tasks can be done simultaneously.

• If only a small part program done same time, adding more threads doesn't make it faster.