Final answer:
A pure ULT facility involves the application handling all aspects of thread management, without the kernel's knowledge.
This means that thread creation, scheduling, and synchronization are done at the user level. Kernel-Level Threading is an alternative where the OS directly manages threads, providing better efficiency in some cases.
Step-by-step explanation:
In a pure ULT (User-Level Threading) facility, the application handles all aspects of thread management, and the kernel is not aware of the existence of threads. This means that thread creation, scheduling, and synchronization are all done at the user level rather than the operating system level.
A common example of ULT is the pthread library in C or C++. With ULT, the application has full control over the threads, and the kernel sees each thread as a single process. However, ULT can be less efficient than Kernel-Level Threading (KLT) in certain scenarios.
In contrast, with KLT, the operating system kernel manages the threads directly. Each thread is treated as a separate entity by the kernel, allowing for more efficient scheduling and better resource utilization.
The question pertains to User-Level Threads (ULT), which are managed entirely by the user-level library and not by the operating system kernel. In a pure ULT environment, the kernel remains unaware of the threads that the application has created and maintains. Since the operating system doesn’t manage thread lifecycle or scheduling, the application must handle all aspects of thread management, including creation, synchronization, and cleanup operations through a user-level library.
This approach has benefits, such as reduced overhead from system calls to the kernel, as well as drawbacks, including the lack of true parallel execution since the operating system's scheduler does not recognize individual threads for CPU allocation.