foreword
Hello everyone, welcome to the YY drop Linux series, a warm welcome! The main content of this chapter is aimed at veterans who have been in touch with Linux, and introduces the process from the operating system level:
the main content includes:
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Article directory
1. The core concept of operating system management: "Describe first and then organize"
- The process of management is a process of "describing first and then organizing".
1. The application of "describe first and then organize" in daily life
- The principal needs to manage students and the principal has limited energy and will not contact each student one by one, so a middleman (executor)-counselor is needed to manage;
- According to the attributes, the counselor first describes "students" as a collection of attributes, such as: a collection of colleges, majors, and classes, that is, a structure;
- Finally, connect the information of each student through a data structure such as a linked list to complete the organization ;
- Since then, the principal's management of students has been successfully transformed into adding, deleting, checking and modifying linked lists ;
2. The application of "describe first and then organize" in the operating system
- Similarly, in the computer ecology, the [operating system] needs to manage the [object] and does not meet with it. The medium between them is the [drive system];
- In the same way, in the operating system, managing any object can eventually be transformed into adding, deleting, checking and modifying a certain data structure ;
- It is also doomed that there are a large number of data structures in the operating system, and the entity of this description is PCB;
2.PCB articles
1.PCB
- Process information is placed in a data structure called a process control block, which can be understood as a collection of process attributes .
- It is called PCB (process control block) in the textbook, and the PCB under the Linux operating system is: task_struct (detailed in the PCB detailed explanation below)
2. Detailed explanation of "task struct" in "Description process-PCB"
PCB:
- Process information is placed in a data structure called a process control block, which can be understood as a collection of process attributes .
- It is called PCB (process control block) in the textbook, and the PCB under the Linux operating system is: task_struct.
A type of task_struct-PCB:
- The structure describing the process in Linux is called task_struct.
- task_struct is a data structure of the Linux kernel that is loaded into RAM (memory) and contains process information
task_ struct content classification:
- Identifier: Describe the unique identifier of this process, which is used to distinguish other processes.
- Status: Task status, exit code, exit signal, etc.
- Priority: Priority relative to other processes.
- Program Counter: The address of the next instruction in the program to be executed.
- Memory pointers: including pointers to program code and process-related data, as well as pointers to memory blocks shared with other processes
- Context data: The data in the registers of the processor when the process is executed [example of suspension of studies, to add pictures of CPU, registers].
- I/O status information: including displayed I/O requests, I/O devices assigned to the process and a list of files used by the process.
- Billing information: May include sum of processor time, sum of clocks used, time limits, billing account number, etc.
- other information
3. Process articles
1. Process
- Textbook concept: an execution instance of a program, a program that is being executed, etc. / a program that has been loaded into memory .
- Kernel point of view: Acts as the entity that allocates system resources (CPU time, memory).
2. The basic structure of the process
- The process includes: [PCB] + [code, data]
