Understanding the Linux® Virtual Memory Manager

Understanding the Linux® Virtual Memory Manager

by Mel Gorman

In Chapter 1, we go into detail on how the source code may be managed and

deciphered. Three tools are introduced that are used for analysis, easy browsing

and management of code. The main tools are the Linux Cross Referencing (LXR)

tool, which allows source code to be browsed as a Web page, and CodeViz, which

was developed while researching this book, for generating call graphs. The last

tool, PatchSet, is for managing kernels and the application of patches. Applying

patches manually can be time consuming, and using version control software, such

as Concurrent Versions Systems (CVS) (http://www.cvshome.org/) or BitKeeper

(http://www.bitmover.com), is not always an option. With PatchSet, a simple specification

file determines what source to use, what patches to apply and what kernel

configuration to use.

In the subsequent chapters, each part of the Linux VM implementation is discussed

in detail, such as how memory is described in an architecture-independent

manner, how processes manage their memory, how the specific allocators work and

so on. Each chapter will refer to other sources that describe the behavior of Linux,

as well as covering in depth the implementation, the functions used and their call

graphs so that the reader will have a clear view of how the code is structured. The

end of each chapter has a “What’s New” section, which introduces what to expect

in the 2.6 VM.

Preface xv

The appendices are a code commentary of a significant percentage of the VM.

They give a line-by-line description of some of the more complex aspects of the VM.

The style of the VM tends to be reasonably consistent, even between major releases

of the kernel, so an in-depth understanding of the 2.4 VM will be an invaluable aid

to understanding the 2.6 kernel when it is released.

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