Review of "Understanding the Linux Kernel" (3^rd edition)

Authors: Daniel Pierre Bovet and Marco Cesati
Publisher: O'Reilly
Review by: Cosimo
Rating:
Date: 2006/05/07

This book is entirely dedicated to the Linux Kernel. This is its 3^rd edition. The first, published in 2000, was based on 2.2 kernel. The second, of the end of 2002, was about 2.4. This one is based on 2.6.11.

The authors, Daniel Bovet and Marco Cesati, teach in Tor Vergata Rome University using Linux as "learning material" for their operating systems classes.

The book is more than 900 pages, in 20 chapters, 2 appendixes and an analytical Linux source code index. There are many arguments, from low level (memory management, processes, interrupts) to high level (device drivers, ext2/3 filesystems and executable files).

The reference architecture is x86, which is somewhat simpler. However the book remarks clearly the platform-independent principles, valid for all the architectures.

Throughout the book, several code fragments from Linux source are dissected and analyzed in detail. In these cases, it is useful to have at least a basic knowledge of C language, maybe even some rough idea of Assembler.

Very interesting is the 7th chapter about Process Scheduling. It explains the "new" process scheduling algorithm adopted in 2.6 kernels, that executes in constant time, no matter the number of running processes.
The previous scheduling mechanism (kernel 2.4) and all the involved data structures are presented, analyzing the transition to the new algorithm, and how the adoption of different data structures helped achieving this spectacular improvement.

One of the big wins of this book is that it helps studying Linux, giving a minimal walk-through guide for the huge kernel source code.

In some parts of the book, like memory pages cache or interrupt management, there are implementation detail explanations of kernel functions with long lists of algorithm steps (even 30!).
Reading those lists without source code at hand is not feasible. They can be useful as references, though.

Conclusions

A very good book, interesting and complete. I'd suggest it to those interested in studying how Linux works and it has been developed.

Pros

• Complete and detailed explanations
• Every main aspect of the kernel is explained, with relevant data structures and involved algorithms.
• Where necessary, hardware-level detail is presented.
• The book can be a useful walk-through for our preferred OS :-)

Cons

• Some parts are too full of "gory" details, and they don't help the reading.
• Basic knowledge of C and (few) Assembler is required. Is it really a bad thing?