LINUX系统调用mlock的代码分析,在LINUX中，每一个用户进程都可以访问4GB的线性虚拟内存空间。其中从0到3GB的虚拟内存地址是用户空间，用户进程可以直接对其进行访问。从3GB到4GB的虚拟内存地址为核心空间，存放仅供核心态访问的代码和数据，用户进程不可访问。当用户进程通过中断或系统调用对其访问时，就会触发处理器的特权级转换（从处理器的特权级3切换到特权级0），即从操作系统的用户态切换到核心态。-Linux system call mlock code analysis, LINUX, Each user process can visit the linear 4 GB of virtual memory space. Them from 0-3 GB of virtual memory address space users, users can direct the process of their visit. From 3 GB to 4 GB of virtual memory address space at the core, the core is for storing state visit to the code and data user process can not visit. When the user through the process of interruption or system call their visit, Processor will trigger the conversion privilege level (from the privileged class processors switched to the three-level privileges 0), from the operating system users switched to the core state.