Implement Thread in User Space

A thread is a lightweight of process. It is a basic unit of CPU utilization which consists of a program counter, a stack, and a set of registers.

Given below is the structure of single threaded process −

Thread in user space

Now, let us see how to implement thread in User Space.

Step 1 − The complete thread package is placed in the user space and the kernel has no knowledge about it.

Step 2 − Kernel generally, manages ordinary and single threaded processes.

Step 3 − Threads are always run on top of a run-time system.

Step 4 − Run time system is a collection of procedures which manage threads.

For example − pthread create,

pthread exit,

pthread join, and

pthread yield,

Step 5 − Each process requires its own private thread table to keep track of the threads in that process.

Step 6 − The thread table always keeps a track on each thread’s properties.

Step 7 − The thread tables are managed by the runtime system.

Given below is an image depicting the implementation of thread in user space −

Advantages

The advantages of implementing thread in user space are as follows −

• OSes that do not support thread and thread are implemented by the library.

• It doesn’t require any modification in the operating system.

• It always gives better performance because there is no context switching involved from the kernel.

• Each process has its own scheduling algorithm.

Disadvantages

The disadvantages of implementing thread in user space are as follows −

• Implementing blocking system calls leads all threads to stop.

• If a thread starts running, then no other thread can run unless the thread voluntarily leaves the CPU.