What are the memory management technologies and methods of Linux?

Linux is an open source operating system that is widely used in various fields due to its stability and high degree of customizability. Memory management is one of the important components of the Linux system. It is responsible for managing the computer's memory resources and providing sufficient memory space for programs. This article will introduce commonly used methods in Linux memory management and provide specific code examples.

1. Paging memory management
   Paging is one of the most commonly used memory management methods in Linux. In paged memory management, memory is divided into fixed-size page frames, each page frame size is usually 4KB. The operating system divides a program's address space into pages, which are mapped into page frames of physical memory. When a program needs to access a memory address, the system loads the required page frame into physical memory for program access.

The following is a sample code snippet that demonstrates how to perform paged memory management in Linux:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>

#define PAGE_SIZE 4096

int main() {
    int fd = open("/dev/zero", O_RDWR);  // 打开/dev/zero设备文件
    void* addr = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);  // 映射一页内存
    
    if (addr == MAP_FAILED) {
        perror("mmap");
        return -1;
    }
    
    // 在页内存中进行读写操作
    char* page = (char*)addr;
    page[0] = 'H';
    page[1] = 'e';
    page[2] = 'l';
    page[3] = 'l';
    page[4] = 'o';
    
    printf("Content of page: %s
", page);
    
    munmap(addr, PAGE_SIZE);  // 取消内存映射
    close(fd);  // 关闭文件描述符

    return 0;
}

2. Memory partition management
   Memory partition management is another A commonly used memory management method. In this method, the operating system divides the memory according to different needs, such as the memory space required by the user mode process, the memory space required by the kernel mode, etc. Each partition has different access rights and usage rules.

The following is a sample code snippet that demonstrates how to perform memory partition management operations in Linux:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#define USER_MEMORY_SIZE (1 << 30)  // 用户态进程所需的内存大小
#define KERNEL_MEMORY_SIZE (1 << 20)  // 内核态所需的内存大小

int main() {
    void* user_memory = malloc(USER_MEMORY_SIZE);  // 分配用户态进程的内存
    void* kernel_memory = malloc(KERNEL_MEMORY_SIZE);  // 分配内核态的内存
    
    if (user_memory == NULL || kernel_memory == NULL) {
        perror("malloc");
        return -1;
    }
    
    // 在用户态内存中进行读写操作
    int* user_data = (int*)user_memory;
    user_data[0] = 42;
    
    printf("Value in user memory: %d
", user_data[0]);
    
    // 在内核态内存中进行读写操作
    int* kernel_data = (int*)kernel_memory;
    kernel_data[0] = 24;
    
    printf("Value in kernel memory: %d
", kernel_data[0]);
    
    free(user_memory);  // 释放用户态内存
    free(kernel_memory);  // 释放内核态内存

    return 0;
}

The above are two commonly used methods in Linux memory management, and the corresponding code example. These methods can help programs use memory resources more efficiently and improve system performance and stability. At the same time, by in-depth understanding of Linux memory management methods, developers can better optimize program performance and reduce the occurrence of problems such as memory leaks.

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