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Multithreading Models in Operating System

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Prerita Agarwal
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23 Jul, 2024 @ 01:30 PM


Hey, Ninjas, let us see an example to understand Multithreading better.

You for sure must have encountered some complex problems somewhere while learning some programming language. What do you do there? You break the code into different functions, right? Multithreading is also a similar concept. In Multithreading, an application divides its task into individual threads. Several threads can accomplish the exact process or task in Multithreading, or we can say that the operation is performed by more than one thread. In other words, Multithreading can be used to achieve multitasking.

Operating Systems

By now, you must be curious enough to learn more about Multithreading. So let us dig deeper into the topic where we will find different types of Multithreading Models, and we will also see an example to understand the subject better.

Also Read,

Multi-Threading Models in OS

As we saw above, Multithreading allows an application to divide its work into threads. Various threads can complete a process. Multithreading helps to enable multitasking. 

The fundamental disadvantage of single threading systems is that the system can complete only one work. To address the above limitation, Multithreading is used, which allows several activities to be completed simultaneously. 

Hey, wait. You must be wondering what this thread is.

A thread is the flow of execution through the process code with its program counter to track which instruction to execute next. The system registers to maintain its current working variables and a stack to keep track of the execution history.

The user-level and kernel-level threads are the two types of threads in an Operating System. User-level threads operated independently of the kernel, allowing them to function without kernel support. On the other hand, the operating system manages kernel-level threads directly. Nonetheless, user-level and kernel-level threads must have some interaction. 

There are three established multithreading models:

  1. Many to one multithreading model
  2. One-to-one multithreading model
  3. Many to many multithreading models
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Many to One Model

Many user-level threads are mapped to one kernel thread in the many-to-one architecture. This sort of connection makes it easier to create an efficient context-switching environment, even on a bare kernel with no thread support.

Many to One Model

Many to One multithreading

The only lag in the architecture is that it cannot make use of the hardware acceleration afforded by multithreaded processes or multi-processor systems since there is only one kernel-level thread scheduling at any given moment. All thread management is done in userspace in this case. This model blocks the entire system if blocking occurs.

One to One Model

In the one-to-one architecture, a single user-level thread is mapped to a single kernel-level thread. In this form of connection, numerous threads are executed at the same time. This advantage, however, comes with a disadvantage. Every new user thread must be accompanied by creating a kernel thread, resulting in overhead that might degrade the parent process's performance. The Windows and Linux operating systems aim to solve this problem by restricting the number of threads created.

One to One Model

 One-to-one multithreading

Many to Many Model

There are numerous user-level threads and several kernel-level threads in this approach. The application determines the number of kernel threads generated. The developer can build as many threads as he wants at both levels, but they may not all be the same. The many to many models is a hybrid of the two previous concepts. If a thread performs a blocked system call under this model, the kernel can schedule another thread to execute. In addition, the inclusion of many threads eliminates the complexity that existed in prior models. Although this paradigm allows for many kernel threads, it cannot achieve total concurrency. This is due to the kernel's ability only to schedule one process at a time.

Many to Many Model

Many to many multithreading models

Also, see Benefits of Multithreading

Frequently Asked Questions

Which thread model is much more efficient in Multithreading?

The user-level thread and the kernel-level thread have a one-to-one relationship. The many-to-one model provides less concurrency than this architecture. Another thread can run when a thread performs a blocking system call. On microprocessors, it allows numerous threads to run in parallel.

What are multithreading models?

Multithreading models define how threads interact within a process. They include many-to-one, one-to-one, and many-to-many models.

What are the three types of multithreading models?

The three types of multithreading models are many-to-one, one-to-one, and many-to-many. These models dictate the relationship between user threads and kernel threads.

Why is the multithreading model more useful in an OS?

The multithreading model is more useful in an OS because it enhances responsiveness, resource utilization, and overall system performance. It allows for better multitasking by executing multiple threads simultaneously, exploiting parallelism in modern processors.


We briefly read about the multitasking operating system and its different types in the article. Then we dug into the multithreading model, where we found it, and saw its three types of models in detail.

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Topics covered
Multi-Threading Models in OS
Many to One Model
One to One Model
Many to Many Model
Frequently Asked Questions
Which thread model is much more efficient in Multithreading?
What are multithreading models?
What are the three types of multithreading models?
Why is the multithreading model more useful in an OS?