$ g++ eat_memory.cpp -o eat_memory

eat_memory.cpp

#include <stdlib.h>
#include <sys/mman.h>
#include <string.h>
#include <stdio.h>

int main(int argc, char** argv) {
    size_t size = atoi(argv[1]) * 1024LL * 1024LL * 1024LL;
    printf("%lu\n", size);
    void *ptr = malloc(size);
    memset(ptr, 0xff, size);
    mlock(ptr, size);
    int c;
    scanf("%d", &c);
    return 0;
}