Book Image

Mastering Linux Kernel Development

By : CH Raghav Maruthi
Book Image

Mastering Linux Kernel Development

By: CH Raghav Maruthi

Overview of this book

Mastering Linux Kernel Development looks at the Linux kernel, its internal arrangement and design, and various core subsystems, helping you to gain significant understanding of this open source marvel. You will look at how the Linux kernel, which possesses a kind of collective intelligence thanks to its scores of contributors, remains so elegant owing to its great design. This book also looks at all the key kernel code, core data structures, functions, and macros, giving you a comprehensive foundation of the implementation details of the kernel’s core services and mechanisms. You will also look at the Linux kernel as well-designed software, which gives us insights into software design in general that are easily scalable yet fundamentally strong and safe. By the end of this book, you will have considerable understanding of and appreciation for the Linux kernel.
Table of Contents (19 chapters)
Title Page
Credits
About the Author
About the Reviewer
www.PacktPub.com
Customer Feedback
Preface
Index

Zones and nodes


Principal data structures that are elementary for entire memory management framework are zones and nodes. Let's familiarize ourselves with core concepts behind these data structures.

Memory zones

For efficient management of memory allocations, physical pages are organized into groups called zones. Pages in each zone are utilized for specific needs like DMA, high memory, and other regular allocation needs. An enum in kernel header mmzone.h declares zone constants:

/* include/linux/mmzone.h */
enum zone_type {
#ifdef CONFIG_ZONE_DMA
ZONE_DMA,
#endif
#ifdef CONFIG_ZONE_DMA32
 ZONE_DMA32,
#endif
#ifdef CONFIG_HIGHMEM
 ZONE_HIGHMEM,
#endif
 ZONE_MOVABLE,
#ifdef CONFIG_ZONE_DEVICE
 ZONE_DEVICE,
#endif
 __MAX_NR_ZONES
};

ZONE_DMA: Pages in this zone are reserved for devices which cannot initiate DMA on all addressable memory. Size of this zone is architecture specific:

Architecture

Limit

parsic, ia64, sparc

<4G

s390

<2G

ARM

variable

alpha

unlimited or <16MB

alpha, i386, x86-64

<16MB...