#include <stdlib.h>
#include <sys/time.h>
#include <sys/user.h>
#include <sys/resource.h>
#include <unistd.h>

scan_mem(int *base, int size)
{
	int sum = 0;

	while (size > 0) {
		sum += *base++;
		size -= sizeof (int);
	}
}

usage_report(struct rusage *prev_ru, int npages)
{
	struct rusage ru;
	float fltim;
	float ofltim;
	int newline = 0;

	getrusage(RUSAGE_SELF, &ru);
	fltim = ru.ru_utime.tv_sec;
	fltim += ((float)ru.ru_utime.tv_usec)/1.0e06;
	ofltim = prev_ru->ru_utime.tv_sec;
	ofltim += ((float)prev_ru->ru_utime.tv_usec)/1.0e06;
	printf("user %.2f", fltim - ofltim);
	fltim = ru.ru_stime.tv_sec;
	fltim += ((float)ru.ru_stime.tv_usec)/1.0e06;
	ofltim = prev_ru->ru_stime.tv_sec;
	ofltim += ((float)prev_ru->ru_stime.tv_usec)/1.0e06;
	printf(" sys %.2f", fltim - ofltim);
	printf(" reclaims: %d faults %d swaps: %d in/out %d/%d csw %d/%d\n",
	    ru.ru_minflt - prev_ru->ru_minflt,
	    ru.ru_majflt - prev_ru->ru_majflt,
	    ru.ru_nswap - prev_ru->ru_nswap,
	    ru.ru_inblock - prev_ru->ru_inblock,
	    ru.ru_oublock - prev_ru->ru_oublock,
	    ru.ru_nvcsw - prev_ru->ru_nvcsw,
	    ru.ru_nivcsw - prev_ru->ru_nivcsw);
	if (npages == 0)
		return; /* should not happen */
	if (ru.ru_minflt - prev_ru->ru_minflt > 0) {
		printf("minor flts/pg: %d ",
		    (ru.ru_minflt - prev_ru->ru_minflt)/npages);
		newline++;
	}
	if (ru.ru_majflt - prev_ru->ru_majflt > 0) {
		printf("major flts/pg: %d ",
		    (ru.ru_majflt - prev_ru->ru_majflt)/npages);
		newline++;
	}
	if (newline) {
		printf("\n");
	}
}

#define SZ2PG(x)	((x + PAGE_SIZE - 1)/PAGE_SIZE)
main(int argc, char *argv[])
{
	int size = 512;
	int tot_size = 0;
	int loops = 0;
	int *p;
	int *base = sbrk(1);
	int max_size;
	struct rusage ru;

	if (argc > 1) {
		max_size = atoi(argv[1]);
		printf("Stop growing after crossing %d bytes\n", max_size);
	} else {
		max_size = 2000000000;
	}
	while ((p = sbrk(size)) != (int *)-1) {
		printf("Touching %d newly allocated bytes.  Size: %d pages/%d "
		    "bytes\n", size, SZ2PG(tot_size), tot_size);
		memset(p, loops, size);
		tot_size += size;
		scan_mem(base, tot_size);
		size <<= 1;
		loops++;
		if (tot_size + size > max_size)
			break;
	}
	printf("Begin doing smaller chunks to finish the job...\n");
	while (size > 4096) {
		size >>= 1;
		p = sbrk(size);
		if (p == (int *)-1)
			continue;
		printf("Touching %d newly allocated bytes.  Size: %d pages/%d "
		    "bytes\n", size, SZ2PG(tot_size), tot_size);
		tot_size += size;
	}
	printf("Finished growing memory.  %d pages\n", SZ2PG(tot_size));
	memset(&ru, 0, sizeof (ru));
	usage_report(&ru, SZ2PG(tot_size));
	getrusage(RUSAGE_SELF, &ru);
	printf("Now scan memory... total size: %d pages/%d. bytes\n", SZ2PG(tot_size), tot_size);
	for (loops = 5; loops > 0; loops--) {
		scan_mem(base, tot_size);
		/*usage_report(&ru, SZ2PG(tot_size));*/
		/*getrusage(RUSAGE_SELF, &ru);*/
		printf("%d scans remaining...\n", loops);
	}
	printf("Overall usage:  (%d pages in this run)\n", SZ2PG(tot_size));
	memset(&ru, 0, sizeof (ru));
	usage_report(&ru, SZ2PG(tot_size));
}