Question

Explain how a “lightweight process” can be used to obtain more control over thread scheduling than simple kernel level threads. (Assume, for your answer, that the OS doesn’t not have priorities for individual threads)

Answer 1

A lightweight process or user-level threads are the single sequence streams within a process. They are used to perform different tasks within the same process. Threads are used to improve the running of a program by implementing concurrency and lesser context switching.

Thread scheduling is the process of allowing a thread which is in a ready state to be executed by the CPU.

Simple kernel-level threads are kernel entities like interrupt handlers. It is an entity that is handled by the system scheduler. It may be referenced by any other thread in the system but a programmer has no direct control over them.

A user-level thread is handled by the programmer and it allows the programmer to control multiple flows fo the program. The scheduling of this is independent of the system scheduler hence much faster.

The system scheduler is responsible for scheduling threads as well as processes, hence each kernel-level thread requires TCB, which increases the complexity of context switching.

Hence using user-level threads over kernel-level threads gives a programmer more freedom to schedule threads