mem-io.c

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

#define BLOCKSIZE 1048576
#define N 200
#define BUSYTIME 1000

int main(int argc, char *argv[]) {
    int fd;
    if ((fd = open("log.txt", O_WRONLY | O_CREAT | O_APPEND, S_IRUSR | S_IWUSR)) == -1) {
        fprintf(stderr, "open file failed\n");
    }

    int **p = malloc(N * sizeof(int*));;
    int i;
    while (1) {
        for (i = 0; i < N; i++) {
            p[i] = malloc(BLOCKSIZE);
            memset(p[i], '0', BLOCKSIZE);
            int j;
            char *q = (char *)(p[i]);
            for (j = 0; j < BLOCKSIZE; j++) {
                q[j] = 'c';
            }
            write(fd, q, BLOCKSIZE);
            usleep(BUSYTIME);
        }

        // fprintf(stderr, "malloced\n");

        for (i = 0; i < N; i++) {
                free(p[i]);
                usleep(BUSYTIME);
        }
        // fprintf(stderr, "freed\n");
    }
}