Monolithic Kernel and key differences from Microkernel

Apart from microkernel, Monolithic Kernel is another classification of Kernel. Like microkernel, this one also manages system resources between application and hardware, but user services and kernel services are implemented under the same address space. It increases the size of the kernel, thus increasing the size of the operating system as well.  This kernel provides CPU scheduling, memory management, file management, and other operating system functions through system calls. As both services are implemented under the same address space, this makes operating system execution faster. 

Below is the diagrammatic representation of the Monolithic Kernel: 

Monolithic Kernel

If any service fails the entire system crashes, and it is one of the drawbacks of this kernel. The entire operating system needs modification if the user adds a new service. 

Advantages of Monolithic Kernel:

1. One of the major advantages of having a monolithic kernel is that it provides CPU scheduling, memory management, file management, and other operating system functions through system calls.
2. The other one is that it is a single large process running entirely in a single address space.
3. It is a single static binary file. Examples of some Monolithic Kernel-based OSs are Unix, Linux, Open VMS, XTS-400, z/TPF.

Disadvantages of Monolithic Kernel –

1. One of the major disadvantages of a monolithic kernel is that if anyone service fails it leads to an entire system failure.
2. If the user has to add any new service. The user needs to modify the entire operating system.

A monolithic kernel is a type of operating system kernel in which all the operating system services run in kernel space, meaning they all share the same memory space. This type of kernel is characterized by its tight integration of system services and its high performance.

On the other hand, a microkernel is a type of operating system kernel in which only the most basic services run in kernel space, with other services running in user space. This type of kernel is characterized by its modularity, simplicity, and ability to run multiple operating systems on the same hardware.

Here are some key differences between monolithic and microkernel architectures:

• System services: In a monolithic kernel, all system services run in kernel space, whereas in a microkernel, only the most basic services (such as memory management and process scheduling) run in kernel space, with other services running in user space.
• Performance: Monolithic kernels are generally faster and more efficient than microkernels, because there is no overhead associated with moving data between kernel space and user space.
• Modularity: Microkernels are more modular than monolithic kernels, because services are separated into different processes running in user space. This makes it easier to add or remove services without affecting other parts of the system.
• Security: Microkernels are generally considered more secure than monolithic kernels, because a bug or vulnerability in a service running in user space is less likely to affect the entire system.
• Development: Developing a monolithic kernel is generally simpler and faster than developing a microkernel, because all system services are integrated and share the same memory space.

In summary, monolithic kernels are characterized by their tight integration of system services and high performance, while microkernels are characterized by their modularity, simplicity, and security. The choice between a monolithic and microkernel architecture depends on the specific needs and requirements of the operating system being developed.

Key differences between Monolithic Kernel and Microkernel are as follows:

Basics	Micro Kernel	Monolithic Kernel
Size	Smaller in	Larger as OS and user both lie in the same address space.
Execution	Slower	Faster
Extendible	Easily extendible	Complex to extend
Security	If the service crashes then there is no effect on working on the microkernel.	If the process/service crashes, the whole system crashes as both user and OS were in the same address space.
Code	More code is required to write a microkernel.	Less code is required to write a monolithic kernel.
Examples	L4Linux, macOS	Windows, Linux BSD
Security	More secure because only essential services run in kernel mode	Susceptible to security vulnerabilities due to the amount of code running in kernel mode
Platform independence	More portable because most drivers and services run in user space	Less portable due to direct hardware access
Communication	Message passing between user-space servers	Direct function calls within kernel
Performance	Lower due to message passing and more overhead	High due to direct function calls and less overhead

FAQ:

What are some examples of operating systems that use a monolithic kernel?
Examples of monolithic kernel-based operating systems include Unix, Linux, Open VMS, XTS-400, and z/TPF.

What are some examples of operating systems that use a microkernel?
Examples of microkernel-based operating systems include L4Linux and macOS.

Which kernel architecture is more secure?
Microkernels are generally considered more secure than monolithic kernels because a bug or vulnerability in a service running in user space is less likely to affect the entire system.

Which kernel architecture is more modular?
Microkernels are more modular than monolithic kernels because services are separated into different processes running in user space. This makes it easier to add or remove services without affecting other parts of the system.

Which kernel architecture has better performance?
Monolithic kernels are generally faster and more efficient than microkernels because there is no overhead associated with moving data between kernel space and user space. However, this may vary depending on the specific needs and requirements of the operating system being developed.