Linux Kernel development (1)

asm/thread_info.h
linux/threads.h /proc/sys/kernel/pid_max
linux/sched.h
kernel/fork.c
linux/kthread.h struct task_struct *kthread_create
Process Priority

1. Process Priority
2. Timeslice
3. The Scheduling Policy in Action

Specifically, CFS determines that the text editor has run for less time than the video encoder. Attempting to give all processes a fair share of the processor, it then preempts the video encoder and enables the text editor to run.
Scheduler Classes

1. Process Scheduling in Unix Systems
2. Fair Scheduling

Each scheduler class has a priority.The base scheduler code, which is defined in kernel/sched.c, iterates over each scheduler class in order of priority.
CFS is defined in kernel/sched_fair.c.
The Linux Scheduling Implementation
With the discussion of the motivation for and logic of CFS behind us, we can now explore CFS’s actual implementation, which lives in kernel/sched_fair.c.

1. Time Accounting: The Scheduler Entity Structure; The Virtual Runtime
2. Process Selection: Picking the Next Task; Adding Processes to the Tree; Removing Processes from the Tree
   This is, in fact, the core of CFS’s scheduling algorithm: Pick the task with the smallest vruntime.That’s it!
3. The Scheduler Entry Point:
   The main entry point into the process schedule is the function schedule(), defined in kernel/sched.c.
4. Sleeping and Waking Up: Wait Queues, Waking Up

Preemption and Context Switching

1. User Preemption
   Calls switch_to(), declared in , to switch the processor state from the previous process’s to the current’s.
2. Kernel Preemption

Real-Time Scheduling Policies

Via the scheduling classes framework, these real-time policies are managed not by the Completely Fair Scheduler, but by a special real-time scheduler, defined in kernel/sched_rt.c.

Scheduler-Related System Calls
Scheduling Policy and Priority-Related System Calls
Processor Affinity System Calls
Yielding Processor Time

延伸阅读