8.2. Microkernels

When I began to write the Linux kernel, there was an accepted school of thought about how to write a portable system. The conventional wisdom was that you had to use a microkernel-style architecture.

With a monolithic kernel such as the Linux kernel, memory is divided into user space and kernel space. Kernel space is where the actual kernel code is loaded, and where memory is allocated for kernel-level operations. Kernel operations include scheduling, process management, signaling, device I/O, paging, and swapping: the core operations that other programs rely on to be taken care of. Because the kernel code includes low-level interaction with the hardware, monolithic kernels appear to be specific to a particular architecture.