Chapter One Linux internal kernel

1. Linux is a UNIX system, but he is not UNIX.

Although Linux borrows a lot of Unix designs and has the UNIX API (as determined by POSIX standards and other single UNIX specification), Linux has no source code that uses UNIX directly like any other UNIX mutation.

2. The Linux system is based on the basic tools of the kernel, C library, toolset, and system, such as the logging program and the shell.

3. The operating system refers to the parts of the system that are responsible for the most basic functions and system management. These should include internal cores, a device driver, an introduction program, a command shell or other user interface, a basic file management tool, and a system tool.

4. Internal nuclear space and user space

• For the modern system of providing the protection system, the internal core is independent of the general application, which is generally in the system, with all the rights of the protected storage space and the visiting hardware. This system and the protected storage space are called internal nuclear space , "he declares.

• In contrast, the application program is executed in the user space . They can only see some of the system resources that allow them to use, and can only use certain system functions, do not access hardware directly, or access the kernel to other people's storage areas, there are other restrictions.

• Inside the core, the system enters internal nuclear space and runs inside the core. When you perform an ordinary user program, the system enters the user space.

5. Applications running in the system pass through the system to communicate with the internal core.

When an application performs a system adjustment, it says that the inner core is acting on its behalf. At this point, the application is called a pass-through system for internal core space, and the inner core is called the run and process context.

6. In Linux, the interrupt service program is not executed in the process context, but in a locked-down context that is not related to all processes. The reason for this is that the warranty service program can be interrupted in the first time and in the process, and then quickly exits.

7. The activity of each processor at any given time:

• Run on user space, perform user processes

• Run the internal core space, execute the process context, and represent a specific process.

• In the internal nuclear space, in the context of the interrupt, with any process, dealing with a particular end

8. When the CPU is idle, the inner core runs an empty process, which is in the process of killing the following, but runs inside the space.

About the knowledge of the idle process, the Internet Digest: Analysis of the Linux kernel idle

9. Linux is a single core, that is, the Linux internal nuclear run in the unique internal core address space.

But Linux draws on the micro core of the essence, such as modular design, hog-occupied core, support the internal nuclear thread and the ability to load the internal core modules. In addition, Linux avoids the defects of performance loss in its micro-core design, allowing all things to be done in the internal nuclear State, directly adjusting the function, without the need for messages to pass.

The difference between Linux kernel and the traditional UNIX system:

• Linux supports dynamic upload of internal core modules

• Linux supports the symmetric multi-processor (SMP) system

• Linux kernel can hog (preemptive). The Linux kernel has the ability to perform a task that allows for internal nuclear transportation.

• Linux internal cores are not divided into threads and other general processes. For Linux kernel, all of the processes are the same--just a few of the shared resources.

• Linux provides a design-oriented model for the equipment, hot plug events, and the user space of the setup file System (SYSFS).

Linux Internal kernel version

Where, from the version number if it is an even number, then the kernel is a stable version, or the release version.

Finish

From for notes (Wiz)

Chapter One Linux internal kernel