MMAP - eat a cake and give it away.

gistfile1.txt

#include <sys/mman.h>

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

const size_t MEM_SIZE = 16 * 1024 * 1024 * 1024llu;

int main() {
	// Allocate memory dynamically
	char *memory = mmap(NULL, MEM_SIZE, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);

	if (memory == MAP_FAILED) {
		perror("Error allocating memory");
		exit(EXIT_FAILURE);
	}

	for (int i = 0; i < 5; ++i){
		// Hint to the operating system that the memory will be needed again soon
		if (madvise(memory, MEM_SIZE, MADV_WILLNEED) == -1) {
			perror("Error advising memory");
			exit(EXIT_FAILURE);
		}

		printf("MADV_WILLNEED done\n");

		fgetc(stdin);

		printf("MEMSET begin\n");

		memset(memory, 0, MEM_SIZE);

		printf("MEMSET done\n");

		fgetc(stdin);

		if (madvise(memory, MEM_SIZE, MADV_DONTNEED) == -1) {
			perror("Error advising memory");
			exit(EXIT_FAILURE);
		}

		printf("MADV_DONTNEED done\n");
		fgetc(stdin);
	}

	// Release memory back to the operating system
	if (munmap(memory, MEM_SIZE) == -1) {
		perror("Error releasing memory");
		exit(EXIT_FAILURE);
	}

	return 0;
}