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Table of contents
1.
Introduction
2.
What is a Thread?
3.
What is Threads in Operating System?
4.
Why Do We Need Thread?
5.
Components of Thread
6.
Needs of Threads
7.
Why Multithreading?
8.
Process vs Thread
9.
Types of threads
9.1.
User-level threads
9.1.1.
Advantages of User-level Threads
9.1.2.
Disadvantages of User-level Threads
9.2.
Kernel-level threads
9.2.1.
Advantages of Kernel-level Threads
9.2.2.
Disadvantages of Kernel-level Threads
10.
Advantages of Threading
11.
Issues with Threading
12.
Frequently Asked Questions 
12.1.
Can threads run on any operating?
12.2.
Why do we need threads in operating system?
12.3.
Is threads an essential part of operating system?
12.4.
What resources are used when thread is created?
12.5.
Which threads are recognized by the OS?
13.
Conclusion
Last Updated: Mar 27, 2024
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Threads in Operating System (OS)

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Introduction

Operating systems is one the most asked topic in interviews. So if you are preparing for interviews, it’s essential to be clear with certain critical topics of the OS. One such important topic is the threads in operating systems. 

Threads in Operating System

This blog will discuss everything you need to know to get started with threads in operating system and their types.

Before understanding threads and their types, let us know what a process is.

What is a Thread?

In computing, a thread refers to a lightweight process that can execute independently of the main program. Threads are a fundamental component of modern operating systems and programming languages, and they allow developers to write concurrent and parallel applications that can perform multiple tasks simultaneously.

In Java, a thread is an instance of the Thread class, which provides methods for creating, starting, and controlling threads. When a Java program is executed, it creates at least one thread, called the main thread, which executes the main() method of the program.

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What is Threads in Operating System?

In an operating system, a thread is a lightweight unit of execution within a process. A process is an instance of a program that is being executed, and a thread is a subset of the process that can run concurrently with other threads within the same process.
Threads share resources with other threads in the same process, such as memory, file handles, and network connections, which makes them more efficient than processes. Because threads are lighter weight than processes, they can be created and destroyed more quickly, and they can switch between tasks more rapidly.
Threads in operating systems can be used to improve the responsiveness and efficiency of multi-tasking applications by allowing different parts of the program to execute concurrently. They can also be used to perform background tasks, such as I/O operations or network communication, without blocking the main thread or other threads.
In modern operating systems, threads are managed by the kernel, which provides services such as scheduling, synchronization, and communication between threads. Operating systems use different thread models, such as the one-to-one model, where each user-level thread is mapped to a kernel thread, or the many-to-many model, where multiple user-level threads can be mapped to a smaller number of kernel threads.

Why Do We Need Thread?

Operating systems need threads for a number of reasons. They allow for concurrent execution within a single process, making it easier to share resources, increase responsiveness, and support parallel processing on multi-core computers. Threads make application architecture simpler, more efficient, and scalable to take full advantage of the available hardware resources. 

They improve I/O-bound operations and are essential for asynchronous programming. In conclusion, threads are essential to contemporary operating systems because they allow for effective and quick program development while using the full power of contemporary hardware.

Components of Thread

Threads are a fundamental component of modern operating systems and programming languages, and they consist of several key components that enable them to perform concurrent and parallel processing. The main components of a thread include:

  • Thread ID
  • Program counter
  • Stack
  • Register set
  • Thread priority
  • Thread state
  • Thread-safety
  • Synchronization

These components work together to enable threads to execute concurrently and perform complex tasks in a parallel and efficient manner.

Needs of Threads

We need threads for several reasons, including:

  1. Improved performance: Threads can help improve the performance of an application by allowing it to execute multiple tasks concurrently, thereby reducing the overall processing time.
  2. Responsiveness: Threads can help improve the responsiveness of an application by allowing it to respond to user input while performing time-consuming tasks in the background.
  3. Resource sharing: Threads can share resources such as memory, files, and network connections.
  4. Modularity: Threads can help improve the modularity of an application by allowing it to break complex tasks into smaller, more manageable units of work that can be executed concurrently.
  5. Asynchronous processing: Threads can be used to perform asynchronous processing, such as handling input/output operations.
  6. Parallel processing: Threads can enable an application to perform parallel processing.

Why Multithreading?

Multithreading allows an application to execute multiple threads of execution concurrently within a single process. There are several reasons why multithreading is important and useful. Multithreading allows an application to take advantage of modern hardware with multiple cores or processors, which can significantly improve the performance of the application.

Multithreading can help an application respond more quickly to user input by allowing time-consuming tasks to be executed in the background while the application remains responsive to the user. It can enable multiple threads to share resources such as memory and I/O devices.

Process vs Thread

Key Features Processes Threads
Definition A process is an instance of a program that is being executed by the operating system. A thread is a lightweight process that is part of a larger process. 
Using Resources There is a need for more resources and memory. Less resources and memory are needed.
Cost Higher overhead for both creation and management. Lower management and creation costs.
Creation Time More Less
Synchronisation IPC methods are necessary for synchronisation.  Synchronisation utilising shared memory is simpler.
Isolation The processes are isolated. Threads share memory.
Scalability Due to higher resource utilisation, less scalable Ideal for multi-core CPUs, more scalable.
Fault Tolerance One process failure doesn't affect others. One thread issue can impact the entire process.

Types of threads

There are two types of threads in the operating system

  1. User-level threads
  2. Kernel-level threads

User-level threads

User-level threads are supported above the kernel. They are managed without kernel support by the run-time system. 

The kernel does not know anything about the user-level threads.

Advantages of User-level Threads

  • User-level threads are very fast and efficient. The switching between threads takes the same time as a procedural call.
  • Everything can be done without the interference of OS.
  • they are more flexible and can be customized to the specific needs of an application

Disadvantages of User-level Threads

  • OS is unaware of user-level threads, so the scheduler cannot schedule them properly.
  • The entire process will get blocked if one user-level thread performs a blocking operation.
  • that they cannot take advantage of multi-core processors, as only a single thread can run on a single core at any given time.

Kernel-level threads

Kernel-level threads are supported and managed by the operating system.

Kernel-level threads are threads that are managed by the operating system's kernel, which provides greater control and visibility into thread execution, but at the cost of increased overhead and potential scalability issues.

Advantages of Kernel-level Threads

  • The kernel is fully aware of kernel-level threads, so the scheduler handles the process better.
  • The kernel can still schedule another thread for execution if one thread is blocked.
  • Kernel-level threads provide better performance because they are managed directly by the operating system, which can schedule them more efficiently than user-level threads.

Disadvantages of Kernel-level Threads

  • It is slower to create and manage than user-level threads and therefore inefficient.
  • The overhead associated with kernel-level threads is that it requires a thread control block.
  • they can lead to resource contention and scheduling overhead due to their heavy use of system resources.

Advantages of Threading

  1. Responsiveness: A multithreaded application increases responsiveness to the user.
  2. Resource Sharing: Resources like code and data are shared between threads, thus allowing a multithreaded application to have several threads of activity within the same address space.
  3. Increased concurrency: Threads may be running parallelly on different processors, increasing concurrency in a multiprocessor machine.
  4. Lesser cost: It costs less to create and context-switch threads than processes.
  5. Lesser context-switch time: Threads take lesser context-switch time than processes.

Issues with Threading

Some common issues with threading include race conditions, deadlocks, and synchronization problems. These issues can occur when multiple threads access shared resources or perform operations that depend on the order of execution. Additionally, multithreading can make it difficult to debug and test code and can lead to performance issues due to overhead and contention for system resources. It is important to carefully design and test multithreaded applications to avoid these issues.

Frequently Asked Questions 

Can threads run on any operating?

Threads are a fundamental feature of modern operating systems and are supported by most operating systems, including Windows, macOS, Linux, and many others.

Why do we need threads in operating system?

Threads are a fundamental feature of modern operating systems because they provide a way to achieve concurrency, which allows multiple tasks to be executed simultaneously on a single processor or across multiple processors.

Is threads an essential part of operating system?

Threads are not necessarily an essential part of an operating system, but they are a fundamental feature that is widely supported by modern operating systems and used by many applications.

What resources are used when thread is created?

Because a thread is a component of a process, it does not consume additional resources when it is created. Instead, it utilizes the memory space of the process from which it was generated.

Which threads are recognized by the OS?

Kernel-level threads are recognized by the OS. These threads are created and managed by the operating system's kernel, which provides the necessary services and resources for thread management.

Conclusion

In this blog, we discussed threads and the type of threads in Operating System. We talked about the user-level and kernel-level threads and the different multithreading models.

Recommended Reading

For detailed knowledge of the operating system check out this Guided Path on Operating System available only on Coding Ninjas Studio. You can also consider our Operating System Course to give your career an edge over others.

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