/* fbig: touch MB megabytes of heap, then time N fork+exec of PROG (median ms).
 * Shows how fork cost grows with the parent's size. Claude Opus 5.5, 2026-10-09. */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/wait.h>

static int cmp(const void *a, const void *b)
{
	double x = *(const double *)a, y = *(const double *)b;
	return (x < y) ? -1 : (x > y);
}

int main(int argc, char **argv)
{
	int mb = atoi(argv[1]), n = atoi(argv[2]), i, st;
	char *heap = (char *)malloc((size_t)mb * 1048576 + 1);
	double *t = (double *)malloc(n * sizeof(double));
	struct timeval a, b;
	pid_t pid;

	memset(heap, 1, (size_t)mb * 1048576);
	for (i = 0; i < n; i++) {
		gettimeofday(&a, NULL);
		if ((pid = fork()) == 0) { execl(argv[3], argv[3], (char *)0); _exit(127); }
		waitpid(pid, &st, 0);
		gettimeofday(&b, NULL);
		t[i] = (b.tv_sec - a.tv_sec) * 1000.0 + (b.tv_usec - a.tv_usec) / 1000.0;
	}
	qsort(t, n, sizeof(double), cmp);
	printf("%4d MB parent: fork+exec min %.2f med %.2f ms\n", mb, t[0], t[n / 2]);
	return 0;
}