Understanding the Linux Kernel

Organization of the Material

When starting to write this book, we were faced with a critical decision: should we refer to a specific hardware platform or skip the hardware-dependent details and concentrate on the pure hardware-independent parts of the kernel?

Others books on Linux kernel internals have chosen the latter approach; we decided to adopt the former one for the following reasons:

• Efficient kernels take advantage of most available hardware features, such as addressing techniques, caches, processor exceptions, special instructions, processor control registers, and so on. If we want to convince you that the kernel indeed does quite a good job in performing a specific task, we must first tell what kind of support comes from the hardware.

• Even if a large portion of a Unix kernel source code is processor-independent and coded in C language, a small and critical part is coded in assembly language. A thorough knowledge of the kernel thus requires the study of a few assembly language fragments that interact with the hardware.

When covering hardware features, our strategy will be quite simple: just sketch the features that are totally hardware-driven while detailing those that need some software support. In fact, we are interested in kernel design rather than in computer architecture.

The next step consisted of selecting the computer system to be described: although Linux is now running on several kinds of personal computers and workstations, we decided to concentrate on the very ...