mmap,malloc分配随机内存

随机数1G

#cat malloc_rand_1g.c
#include <stdio.h>  /* printf, scanf, NULL */
#include <stdlib.h>  /* malloc, free, rand, system */
#include <unistd.h>
#include <memory.h>

int main ()
{
    int size;
	int	n;
    char * buffer;
	size=1024*1024*1024; //1G
    printf ("输入字符串的长度：%d bytes\n",size);
	//scanf ("%d", &i);

    buffer = (char*)malloc(sizeof(char) * size);  // 字符串最后包含 \0
    if(buffer==NULL) exit(1);  // 判断是否分配成功

	memset(buffer,'a',sizeof(char) * size);
	printf("total bytes:%d bytes \n",sizeof(char) * size);
    // 随机生成字符串
    for(n=0; n<size; n++){
        buffer[n] = rand()%26+'a';
//		printf("%c",buffer[n]);
	}
	printf("\n");

    buffer[size+1]='\0';
  //  printf ("随机生成的字符串为：%s\n",buffer);

	printf("wait about 1800s....\n");
	sleep(1800);
    free(buffer);  // 释放内存空间
	printf("clean up....\n");
    return 0;
}

memset(a)

#cat  malloc_a_1g.c
#include <stdio.h>  /* printf, scanf, NULL */
#include <stdlib.h>  /* malloc, free, rand, system */
#include <unistd.h>
#include <memory.h>

int main ()
{
    int size;
	int	n;
    char * buffer;
	size=1024*1024*1024; //1G
    printf ("输入字符串的长度：%d bytes\n",size);
	//scanf ("%d", &i);

    buffer = (char*)malloc(sizeof(char) * size);  // 字符串最后包含 \0
    if(buffer==NULL) exit(1);  // 判断是否分配成功

	memset(buffer,'a',sizeof(char) * size);
	printf("total bytes:%d bytes \n",sizeof(char) * size);
    // 随机生成字符串
    for(n=0; n<size; n++){
        buffer[n] = 'a';
//		printf("%c",buffer[n]);
	}
	printf("\n");

    buffer[size+1]='\0';
  //  printf ("随机生成的字符串为：%s\n",buffer);

	printf("wait about 1800s....\n");
	sleep(1800);
    free(buffer);  // 释放内存空间
	printf("clean up....\n");
    return 0;
}

mmap

#cat mmap_1g.c
#include<stdio.h>
#include<sys/mman.h>
#include<unistd.h>
#include<stdlib.h>
#include<string.h>
#define SIZE  1024*1024*1024
#define GB 1
int main(int argc,char* argv[]) {
    char *p;
	int i=1;
	for (i=1;i<=GB;i++) {
		if ((p = (char *)mmap(NULL,SIZE, PROT_READ |
					PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0)) == (void *)-1) {
			perror("mmap");
		 }
		memset(p,'c',SIZE);
		printf("Get %d GB...\n",i);
	}
	sleep(3000);
	return 0;
}