Microkernel in Operating System: Architecture, Advantages

Before we learn MicroKernel, let's understand:

What is Kernel?

A kernel is an important part of an OS that manages system resources. It also acts as a bridge between the software and hardware of the computer. It is one of the first program which is loaded on start-up after the bootloader. The Kernel is also responsible for offering secure access to the machine's hardware for various programs. It also decides when and how long a certain application uses specific hardware.

In this Operating system tutorial, you will learn:

• What is Kernel?
• What is Microkernel?
• What is a Monolithic Kernel?
• Microkernel Architecture
• Components of Microkernel
• Difference Between Microkernel and Monolithic Kernel
• Advantages of Microkernel
• Disadvantage of Microkernel

What is a Monolithic Kernel?

Monolithic Kernel runs all the basic system services like process management, Memory management, I/O communication, and interrupt handling, file system, etc in kernel space.

In this type of Kernel approach, the entire operating system runs as a single program in kernel mode. The operating system is written as a collection of procedures that are linked together into a large executable binary program.

Microkernel Architecture

A Microkernel is the most important part for correct implementation of an operating system. You can see in the below-given diagram, that Microkernel fulfills basic operations like memory, process scheduling mechanisms, and inter-process communication.

Microkernel is the only software executing at the privileged level. The other important functionalities of the OS are removed from the kernel-mode and run in the user mode. These functionalities may be device drivers, application, file servers, interprocess communication, etc.

Components of Microkernel

A microkernel comprises only the core functionalities of the system. A component is included in the Microkernel only if putting it outside would interrupt the functionality of the system. All other non-essential components should be put in the user mode.

The minimum functionalities required in the Microkernel are:

• Memory management mechanisms like address spaces should be included in the Microkernel. It also contains memory protection features.
• Processor scheduling mechanisms should contain process and thread schedulers.
• Inter-process communication manages the servers that run their own address spaces.

Difference Between Microkernel and Monolithic Kernel

Advantages of Microkernel

Here, are the pros/benefits of using Microkernel

• Microkernel architecture is small and isolated therefore it can function better.
• Microkernels are secure because only those components are included that disrupt the functionality of the system otherwise.
• The expansion of the system is more accessible, so it can be added to the system application without disturbing the Kernel.
• Microkernels are modular, and the different modules can be replaced, reloaded, modified without even touching the Kernel.
• Fewer system crashes when compared with monolithic systems.
• Microkernel interface helps you to enforce a more modular system structure.
• Without recompiling, add new features
• Server malfunction is also isolated as any other user program's malfunction.
• Microkernel system is flexible, so different strategies and APIs, implemented by different servers, which can coexist in the system.
• Increased security and stability will result in a decreased amount of code which runs on kernel mode

Disadvantage of Microkernel

Here, are drawback/cons of using Microkernel:

• Providing services in a microkernel system are expensive compared to the normal monolithic system.
• Context switch or a function call needed when the drivers are implemented as procedures or processes, respectively.
• The performance of a microkernel system can be indifferent and may lead to some problems.

Summary:

• A kernel is an important part of an OS that manages system resources.
• A microkernel is a software or code which contains the required minimum amount of functions, data, and features to implement an operating system.
• In Monolithic Kernel approach, the entire operating system runs as a single program in kernel mode
• A Microkernel is the most important part for correct implementation of an operating system.
• A microkernel comprises only the core functionalities of the system.
• A monolithic kernel is a large process running in a single address space, whereas Microkernel can be broken down into separate processes called servers.
• Microkernel architecture is small and isolated therefore it can function better
• Providing services in a microkernel system are expensive compared to the normal monolithic system