Loose Coupling

Software doesn’t need to know the complexity of hardware. It can use the hardware thought a standard interface called System Call (系统调用)

Preemptive Kernel

Avoid Kernel Hogging

Prevent kernel from hogging the CPU, and slow down user space process

Kernel Module

  • Known as Kernel Extension in the context of MacOS and IOS
  • Extend the functionality of the Kernel
  • FUSE is a kernel Module for example

Kernel Booting

  1. Get configuration info from BIOS
  2. Check for missing Device Driver
  3. Start up Init System
  4. Initialise Page Table
  5. Starts up OS System Program
  6. OS is booted up and ready to be used by the User

Kernel Architecture

Micro Kernel Architecture


If one of the kernel Process (进程) crashes, this doesn’t crash the entire system

Less Performant

Due to the overhead of communication between different modules

Components of Traditional Microkernel

  1. Process Management
  2. Main Memory Management
  3. Inter-Process Communication (IPC)

There are no Device Driver and File System etc

Monolithic Kernel Architecture

  • By far, the most common Kernel architecture, used by Linux Kernel
  • The entire kernel runs as a single program in Kernel Mode
  • Consist of a collection of Procedures, linked together into a single large executable binary program. Each Procedures in the system is free to call any other one


No much overhead to call any of the kernel procedures

Harder to Maintain

Thousands of procedures that can call each other without restriction may also lead to a system that is difficult to understand

Not So Fault-tolerant

A crash in any of these Procedures will take down the entire Kernel