The fourth chapter process dispatching reading notes

4.1 multitasking

Multitasking system is an operating system that can simultaneously interactively execute multiple processes

1. Preemptive multi-tasking

2. Non-preemptive multi-tasking

 

4.2Linux process scheduling

The basis of scheduling program design and the complete Fair scheduler

How to apply

How to design

How to implement

Related system calls

 

4.3 policy

Policy determines when a scheduler will run a process

4.3.1 I/O consumption and processor-consumable processes

Scheduling policies typically seek a balance between two contradictions:

1. The corresponding time is short

2. High throughput

4.3.2 process Priority

1.nice value -20~19

2. Real-time priority 0~99

4.3.3 time slice

Time slice is a value

Represents the time before preemption

4.3.4 Scheduling policy activity

But what happens when the text editor is awakened?

 

4.4 Scheduling algorithm

4.4.1 Scheduler class

4.4.2unix system process scheduling

1. If the nice value is mapped to a time slice, the Nice unit value must correspond to the absolute time of the processor.

2. Design the relative value of Nice

3. To perform a time slice mapping of nice values, we need to allocate an absolute time slice, and this time slice must be within the test range of the kernel.

4. The issue of waking up processes based on the priority scheduler in order to optimize interactive tasks.

4.4.3 Fair Dispatch

A simple idea: the
process scheduling effect should be the same as the system with a perfect multi-tasking processor.

 

4.5LINUX scheduling implementation

Time accounting

Process selection

Scheduler portal

Sleep and wake

 

4.6 preemption and toggle contexts

1. User preemption

2. Kernel preemption

 

4.7 Real-time scheduling policy

4.8

 

Fourth Chapter process dispatch reading notes