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
About the Author
About the Reviewer
Customer Feedback

The scheduler's entry point

The process of scheduling starts with a call to the generic scheduler, that is, the schedule() function, defined in <kernel/sched/core.c>. This is perhaps one of the most invoked routines in the kernel. The functionality of schedule() is to pick the next best runnable task. The pick_next_task() of the schedule() function iterates through all the corresponding functions contained in the scheduler classes and ends up picking the next best task to run. Each scheduler class is linked using a single linked list, which enables the pick_next_task() to iterate through these classes.

Considering that Linux was primarily designed to cater to highly interactive systems, the function first looks for the next best runnable task in the CFS class if there are no higher-priority runnable tasks in any of the other classes (this is done by checking whether the total number of runnable tasks (nr_running) in the runqueue is equal to the total number of runnable tasks in the...