Difference between Micro Kernel and Modular Kernel

Prerequisite – Kernel in Operating System

1. MicroKernel:

Micro Kernel, as the name suggests, is basically a software or code that usually contains a minimum number of functions that are required, data, and features simply to implement OS. It is a very small kernel and represents well studied OS structuring idea. In simple words, micro kernels are required to correctly implement OS.

Features of Microkernel:

• Minimalist design: Microkernel has a minimalist design, with only the most essential functions of the operating system implemented in the kernel.
• High flexibility: Microkernel is highly flexible, with most operating system functions implemented as separate processes running in user space.
• Reliable: The microkernel architecture improves system reliability and stability by isolating the kernel functions from other processes.
• Portable: Microkernel is highly portable, making it easier to implement on different hardware platforms.

2. Modular Kernel:

Modular Kernel, as the name suggests, is a type of kernel in which some parts of the system core will get allocated in independent files called modules. This can be added to the system at run time. It usually requires a small amount of time to load modules. If one needs a new module, then one won’t have to recompile.

Features of Modular Kernel:

• Monolithic design: Modular kernel has a monolithic design, with all operating system functions implemented in the kernel.
• Low flexibility: Modular kernel has low flexibility, as all operating system functions are tightly coupled and cannot be easily modified or replaced.
• Efficient: The modular kernel architecture is efficient, as all operating system functions are implemented within the kernel, reducing the overhead associated with interprocess communication.
• Performance-oriented: Modular kernel is designed for performance-oriented applications, as it provides faster execution of operating system functions.

Similarities between Microkernel and Modular Kernel:

• Both provide the core operating system functions required to run applications.
• Both manage system resources such as memory, CPU, and I/O devices.
• Both can support multi-tasking and multi-user environments.
• Both can provide security and protection mechanisms for system resources.

The difference between MicroKernelhas and Modular Kernel are as follows: 

Micro Kernel	Modular Kernel
It generally provides mechanisms that are required to implement on OS.	It generally allows administrator to add functionality only when it is required.
It provides more security and reliability as compared to modular kernel.	It provides less security and reliability as compared to a a the and micro kernel.
It usually simplifies debugging and system verification changes service without restarting system, etc.	It usually decreases boot time, does not have to load everything at boot time, faster development time, etc.
It simply places code in user space and requires that channels be used to connect code modules.	It simply places any code in any ring that it chooses.
In this, minimal or less functionalities or facilities are required to load further services.	In this, different kernel services are separated into different files so that one can link monolithic kernel with functionality or facilities that are required.
Its main aim is to minimize or reduce kernel and implement as much as possible outside TCB.	Its main aim is to keep what is loaded in boot-time minimal while still enabling kernel to execute more functions that are complex.
It generally includes low-level address space management, IPC (Inter-Process Communication).	It generally includes a simple filesystem driver, built-in native file system driver with other storage modules, etc.

Conclusion:

microkernels and modular kernels differ in their design philosophy, system performance, stability, security, and customizability. Microkernels prioritize minimalism and stability, while modular kernels prioritize functionality and performance. Microkernels have slower system performance but are more stable and secure, while modular kernels have faster system performance but are more prone to failure and attacks. Modular kernels are also more customizable than microkernels.