User space and kernel space, process context and interrupt context [summary]

User space and kernel space, process context and interrupt context [summary]

Recent research to Zabbix monitoring, it is necessary to understand the meaning of the various indicators of the CPU,

1, a brief review of the CPU and computer components:

Computer Five parts: operator controller memory input/output device.

Kernel State and user state of the 2,CPU process

　We know that the operating system is now using virtual memory, then for 32-bit operating systems, its addressing space (virtual storage space) is 4G (2 of 32). The core of the worry system is the kernel, which is independent of the normal application, has access to the protected memory space, and has all the permissions to access the underlying hardware device. In order to ensure that the user process can not directly manipulate the kernel, to ensure the security of the kernel, worry about the system to divide the virtual space into two parts, part of the kernel space, part of the user space. For the Linux operating system, the highest 1G bytes (from the virtual address 0xc0000000 to 0xFFFFFFFF) for the kernel to use, called the kernel space, and the lower 3G bytes (from the virtual address 0x00000000 to 0xBFFFFFFF) for each process to use, Called User space. Each process can enter the kernel through system calls, so the Linux kernel is shared by all processes within the system. Thus, from a specific process perspective, each process can have a virtual space of 4G bytes. The spatial allocation is as follows:

with user space and kernel space, the entire Linux internal structure can be divided into three parts, from the bottom to the top, in order: hardware----------------- as shown in the following:

User space and kernel space, process context and interrupt context [summary]