Linux Core Kernel Commentary

Most Recent Change: Sat Jan 19 06:52:47 2002 UTC.

What's All This, Then?

This is the support site for my Linux book, Linux Core Kernel Commentary. (I regret that I do not offer links to Amazon.com's excellent site, due to their silly stance on patents. I like Amazon.com a lot as a company, and I hope they change their position soon so that I can start sending them business again.)

Linux Core Kernel Commentary (LCKC) closely examines about 50,000 lines of source code at the heart of the Linux kernel: process scheduling, memory management, interprocess communication, and more. It's based on kernel version 2.4.1.

Written in the spirit of the classic Lions' Commentary on Unix, LCKC is a critical examination of the source code as much as it is a guide to selected portions of the kernel's internals. The closest parallel I can think of is literary criticism (not deconstruction, the worthwhile kind) -- here's what the code's authors are doing, here's why, here's how they could have done it better (rarely!).

Veteran kernel hackers won't get much new information out of it. It's really aimed at

Students and others who want to see how a real, modern OS works inside.
Programmers who, like me, are interested in what happens to code in extreme conditions. In the kernel's case, those extreme conditions include unusually strong requirements for speed, clarity, robustness, correctness, portability, and extensibility. The inevitable conflicts among these goals only make the results more interesting.

The publisher, Coriolis, is making a strong entry in the Open Source arena, and my book is just one of several such books in their growing armory. The others include commentary-style books on Apache and on the networking portion of the Linux kernel, non-commentary books such as low-cost bound collections of man pages, and so on. After O'Reilly, Coriolis is probably taking Linux and the free software movement more seriously than any other publisher. Also, they're nice people.

What's New in the Second Edition

The second edition corrects all known errata from the first edition, and it has been generally updated and revised to cover the 2.4-series kernels (the first edition covered kernel version 2.2.5).

And there are some noteworthy additions: most importantly, the second edition covers Linux's slab allocator and buddy system in great detail. These important parts of the memory management code were sadly neglected in the first edition. There are many other important changes distributed throughout the book, in proportion to the changes in the underlying code.

Also, an automatically generated code cross-reference listing (courtesy of generous reader Chris Sears) is supplied on the book's CD-ROM. (The Perl script Chris wrote to generate it is available here on the Web site.) Many thanks, Chris.

If you already own the first edition, should you "upgrade"?

The main focus of this edition was on updating the existing coverage to track changes in the 2.4 kernel. If you are a satisfied owner of the first edition, the second edition might not be worth the money to you (unless you're very interested in the slab allocator and the buddy system, that is), though I encourage you to browse through the book at your local bookstore and make up your own mind. Of course, if you're a new buyer, you'll prefer the second edition.

Errata, Updates, and Other Goodies

I've read through my author's copy and listed all errata I found. If you find a problem in the book -- anything from a glaring inaccuracy to a minor typo -- please email me about it. I'll make the correction available on the errata page and acknowledge you in the next edition. I'll probably also email you a cringing, thoroughly shamefaced apology, which is always the best part.

Praise for the First Edition

I don't know of any online reviews of the second edition yet, but most of the information in the following reviews of the first edition still applies to the second edition:

Source	Full Review	Reviewer's Conclusion
Slashdot	Review by chromatic	"Anyone wondering where to start understanding the Linux kernel would do well to consider this book."
Dr. Dobb's Electronic Review of Computer Books	Review by Lou Grinzo	"Any programmer who wants to understand the core of the Linux kernel in this detail, whether out of curiosity or in connection with a specific project, will find Linux Core Kernel Commentary to be a terrific start."
Linux Weekly News	Review by Jonathan Corbet	"The Linux Core Kernel Commentary is not perfect. Nonetheless, it contains a great deal of good information, and I am glad to have it on my shelf. Those who are interested in digging around in the kernel source will likely want to pick up a copy."

Other First-Edition Stuff

The automatically generated cross-reference (in PDF format; 69KB and 22 pages; updated 2000 Jan 17) and the errata listing for the first edition are still available. Although all known errata from the first edition are corrected in the second edition, I would still appreciate hearing of any undiscovered first-edition errata.

Just For Fun

Check out the LineFinder applet, a little toy that lets you browse the source code included in the book; it requires Java 1.1 support from your browser. Warning: In addition to the applet code itself, LineFinder downloads about 500KB of source code. This may take a few minutes, depending on the speed of your connection. Also beware that this applet seems to hang some versions of Netscape's browser.

And here's what I tried to get Coriolis to use for my About the Author blurb.

lckc@ScottMaxwell.org