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Table of contents
1.
Introduction
2.
What is a Kernel?
3.
What is a Microkernel?
3.1.
Examples of Microkernel
4.
Architecture of Microkernel
5.
Components of Microkernel in Operating System
6.
Advantages of Microkernel Operating System
7.
Disadvantages of Microkernel Operating System
8.
Difference between Monolithic kernel and Microkernel
9.
Frequently Asked Questions
9.1.
What are the benefits of using microkernel structure?
9.2.
Is Windows a microkernel OS?
9.3.
What is an example of a microkernel?
9.4.
What are the different types of Kernel?
10.
Conclusion
Last Updated: Jul 4, 2024
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Microkernel in Operating Systems

Author Jainish Patel
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Introduction

Have you ever wondered how computer applications and software are programmed in a way that they use computer hardware to perform the task? Or how the computer software is integrated with the hardware. 

Operating System

In this article, we will learn about the Microkernel, including its architecture, benefits, and drawbacks. 

Before we start with the Microkernel, let’s understand what is a kernel:

What is a Kernel?

A kernel is a core part of the operating system that manages resources. 

  • It also acts as a bridge between the software and hardware. 
  • It is one of the first programs that start up after Boot-loader.
  • It manages various services such as input and output management, handling various system calls, and so on. Moreover, the kernel resides on a low level of abstraction. 
  • The Kernel is also in charge of providing various programs with secure access to the machine's hardware. 
  • It also determines when and for how long a specific application will use specific hardware.

illustration image

Now let us discuss the Microkernel: 

There are five types of kernel: 

  1. Microkernel 
  2. Monolithic kernel 
  3. Hybrid kernel
  4. Nano kernel
  5. Exo kernel
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What is a Microkernel?

A microkernel is a software or a program that contains both user and kernel services in separate address spaces. Due to which the size of the Microkernel is smaller than that of the Monolithic kernel. As the user services and the kernel services reside in different address spaces, for communication purposes, message passing is used, which makes the execution of the microkernel to be slower. 

Nonetheless, the microkernel is easily extendable. As a result, if a new service needs to be added, no changes to the kernel are required. Furthermore, if a user service fails, it has no effect on the operation of the microkernel.

Let us discuss some more points to understand the microkernel in a better way: 

  • It only provides minimal memory and process management services.
  • Microkernels and their user environments are typically written in the C++ or C programming languages, with a little assembly thrown in for good measure. Other implementation languages, however, are possible with some high-level coding.

Examples of Microkernel

Microkernel examples include -

  • QNX: A real-time operating system known for its reliability and scalability, used in embedded systems, automotive, and medical devices.
  • Minix: Designed for teaching purposes initially, Minix is a Unix-like operating system used in education and research.
  • Symbian: Developed for mobile devices, Symbian featured a microkernel architecture optimized for performance and low memory usage.
  • Mac OS X (XNU): Although primarily monolithic, Mac OS X incorporates elements of microkernel architecture with a hybrid XNU kernel.
  • L4Linux: Combines the L4 microkernel with Linux, leveraging the security and reliability benefits of microkernels with the extensive software support of Linux.
  • Integrity: A real-time operating system with a microkernel design, widely used in aerospace, defense, and automotive industries.
  • K42: A research project exploring microkernel design principles to enhance operating system flexibility and performance.

Architecture of Microkernel

A Microkernel is the most crucial component in the proper operation of an Operating System. Microkernel performs basic functions such as memory management, process scheduling algorithms, and inter-process communication. 

Architecture of Microkernel

In the above figure, Process scheduling algorithms, memory, and interprocess communication are all included. It is the only program that runs at the privileged mode, i.e. kernel mode. The rest of the OS's functions are moved out of kernel mode and run in user mode. Device drivers, applications, file servers, interprocess communication, and so on are examples of these functionalities.

Moreover, the kernel is in charge of the essential services because it is the most important OS component. As a result, only the most important services are present inside the kernel under this design. The rest of the operating system services, on the other hand, are included within the system application software.

The important services for which the microkernel is responsible are:

  • Inter-process communication
  • Scheduling of CPU
  • Memory management
services

1. Inter-Process Communication

The interaction of processes is referred to as interprocess communication. There are several threads in a process. Threads from any process interact with one another in the kernel space. Messages are sent and received via ports across threads. There are several ports at the kernel level, including process port, exceptional port, bootstrap port, and registered port. These ports all interact with user-space processes.

2. Memory Management

Memory management is assigning space in the main memory and to manage different operations between disk and main memory. However, there is also the creation of virtual memory for processes. Virtual memory means that if a process has a bigger size than the main memory, it is partitioned into portions and stored. After that, each part of the process is saved in the main memory one by one until the CPU executes it.

3. CPU Scheduling

CPU SCHEDULING is the process to determine which process will run next in the CPU and which process will be kept on HOLD while the other one is running. All processes are queued and run sequentially. Every process has a priority level, and the highest priority procedure is carried out first. CPU scheduling might help you get the most out of your computer. Furthermore, resources are being utilized more effectively. It also reduces the amount of time spent waiting. 

Components of Microkernel in Operating System

A microkernel incorporates only the core functionalities of the system. Putting a component outside would disrupt the system's functionality if it is incorporated in the Microkernel. All other non-essential components should be run in user mode.

The Microkernel must have the following minimum functionalities:

  • Address spaces and other memory management mechanisms should be incorporated in the Microkernel. It also has memory-protection capabilities.
  • Process and thread schedulers should be included in processor scheduling methods.
  • The servers that run their own address spaces are managed by inter-process communication.

Advantages of Microkernel Operating System

  • Because Microkernel architecture is compact and isolated, it can perform better.
  • Microkernels are safe since only those components are provided that would otherwise disturb the system’s functionality. 
  • It is easily expandable as compared to a monolithic kernel. 
  • Microkernels are modular, and the various modules can be swapped out, reloaded, and modified without affecting the Kernel.
  • When compared to monolithic systems, there are fewer system crashes.
  • The Microkernel interface aids in the implementation of a more modular system structure.
  • The failure of a server is isolated in the same way that the failure of any other user program is isolated.
  • Because the Microkernel system is versatile, various techniques and APIs implemented by multiple servers can coexist in the system.
  • As security and stability improve, the amount of code executed in kernel mode decreases.
  • It is particularly suited to product-based applications, in which we could provide a minimum viable product (MVP) to customers while gradually adding more releases and features with minimal changes.

Disadvantages of Microkernel Operating System

  • Compared to a monolithic system, providing services in a Microkernel system is costly.
  • This architecture is not appropriate for systems that require frequent communications and dependencies between different components.
  • A context switch or a function call is required when the drivers are implemented as procedures or processes.
  • A Microkernel system's performance can be variable, leading to issues.

Let us now discuss the fundamental differences between monolithic kernel and microkernel in detail: 

Difference between Monolithic kernel and Microkernel

Monolithic Kernel

Microkernel

In monolithic kernel, both user and kernel services are present in the same address space. In microkernel, both user and kernel services are present in the different address space. 
Operating system is easy to design and implement. Operating system is complex to design. 
It is a large process that is running in a single space address.It can be broken down into separate processes known as servers. 
Less code is required to write a Monolithic Kernel.More code is required to write a MicroKernel.
If a service gets crashed, the whole system collapse.If a service gets crashed, there is no effect on the working of a MicroKernel.
It is a single static binary file. Servers communicate with each other through IPC.
Some examples of Monolithic Kernel are Linux, BSDs, Microsoft Windows (95,98, Me), Solaris, OS-9, AIX, DOS, XTS-400, etc.Some examples of MicroKernel are L4Linux, QNX, SymbianK42, Mac OS X, Integrity, etc.

Frequently Asked Questions

What are the benefits of using microkernel structure?

Microkernel structure offers modularity, reliability, and security by minimizing the kernel's size, allowing for easier maintenance, flexibility in extending functionality, and isolation of components.

Is Windows a microkernel OS?

No, Windows is not a microkernel OS. It follows a monolithic kernel architecture where core functionalities like memory management and device drivers operate in kernel space.

What is an example of a microkernel?

An example of a microkernel is QNX. It provides a minimalistic kernel that handles essential functions like IPC and memory management, while other services run as user-level processes, enhancing reliability and customization options.

What are the different types of Kernel?

There are basically five types of Kernels as given below:

  • Monolithic Kernel
  • MicroKernel
  • Hybrid Kernel 
  • Nano Kernel
  • Exo Kernel

Conclusion

This article discusses microkernel in operating systems. Microkernel architecture in operating systems offers significant advantages such as modularity, reliability, and security by minimizing kernel size and delegating additional functionalities to user-level processes. While its implementation requires careful consideration of performance trade-offs, the flexibility and potential for customization make microkernels pivotal in modern OS design, especially in domains requiring high reliability and scalability. 

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