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


int main(int argc, char* argv[])
{
    char* memindex[1000] = {0};
    int eat = 0;
    int wait = 0;
    int i = 0;

    if (argc < 2)  {
        printf("Usage: ./eat_release_memory <num>   #allocate num * 8 MB and free num MB memory\n");
        return;
    }

    sscanf(argv[1], "%d", &eat);
    if (eat <= 0 || eat >= 1000) {
        printf("num should larger than 0 and less than 1000\n");
        return;
    }
    printf("Allocate memory in MB size: %d\n", eat * 8);

    printf("Allocation memory Begin!\n");
    for (i = 0; i < eat; i++) {
        memindex[i] = (char*)mmap(NULL, 8*1024*1024, PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
        memset(memindex[i], 0, 8*1024*1024);
    }

    printf("Allocation memory Done!\n");
    sleep(2);
    printf("Now begin to madvise free memory!\n");
    for (i = 0; i < eat; i++) {
        madvise(memindex[i] + 7*1024*1024, 1024*1024, MADV_DONTNEED);
    }
    sleep(5);
    printf("Now begin to release memory!\n");
    for (i = 0; i < eat; i++) {
        munmap(memindex[i], 8*1024*1024);
    }

}