/*
 * Runs a series of tests that randomly access a file.
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/sysctl.h>

#include <assert.h>
#include <err.h>
#include <fcntl.h>
#include <inttypes.h>
#include <stdio.h>
#include <time.h>
#include <unistd.h>

#define	FILE_NAME	"/local/large_file"

#define ITERATIONS	1000000

#define	MAX_BLOCK_SIZE	262144

char block[MAX_BLOCK_SIZE];

void
run(int fd, struct stat *fsp, int read_size, int block_size)
{
	struct timeval tv;
	size_t size;
	long npages, nsplays, opages, osplays;
	off_t largest_off, off, smallest_off;
	int64_t end, start;
	int i;

	printf(" read size: %d\n", read_size);

	largest_off = 0;
	smallest_off = fsp->st_size;

	size = sizeof(osplays);
	sysctlbyname("debug.counter.7", &osplays, &size, NULL, 0);
	assert(size == sizeof(osplays));

	size = sizeof(opages);
	sysctlbyname("debug.counter.8", &opages, &size, NULL, 0);
	assert(size == sizeof(opages));

	gettimeofday(&tv, NULL);
	start = 1000000L * tv.tv_sec + tv.tv_usec;

	for (i = 0; i < ITERATIONS; i++) {
		off = (random() % (fsp->st_size / block_size)) * block_size;
		assert((off & (block_size - 1)) == 0);
		if (off < smallest_off)
			smallest_off = off;
		if (off > largest_off)
			largest_off = off;
		if (lseek(fd, off, SEEK_SET) != off)
			err(1, "lseek");
		if (read(fd, block, read_size) != read_size)
			err(1, "read");
	}

	gettimeofday(&tv, NULL);
	end = 1000000L * tv.tv_sec + tv.tv_usec;

	size = sizeof(nsplays);
	sysctlbyname("debug.counter.7", &nsplays, &size, NULL, 0);
	assert(size == sizeof(nsplays));

	size = sizeof(npages);
	sysctlbyname("debug.counter.8", &npages, &size, NULL, 0);
	assert(size == sizeof(npages));

	/*
	 * Perform a sanity check on the smallest and largest blocks accessed.
	 */
	if (smallest_off > fsp->st_size / 100)
		printf("Warning: smallest off accessed: %ld\n", smallest_off);
	if (largest_off < fsp->st_size - (fsp->st_size / 100))
		printf("Warning: largest off accessed: %ld\n", largest_off);

	printf("  splays: %ld\n", nsplays - osplays);

	printf("  pages/splay: %f\n", (double)(npages - opages) /
	    (nsplays - osplays));

	printf("  usecs/read: %f\n", (double)(end - start) / ITERATIONS);
}

main(int argc, char **argv)
{
	struct stat fs;
	int block_size, fd;

	fd = open(FILE_NAME, O_RDONLY);
	if (fd == -1)
		err(1, "open");
	if (fstat(fd, &fs) == -1 || !S_ISREG(fs.st_mode))
		err(1, "fstat");
	printf("file size: %ld\n", fs.st_size);

	for (block_size = 4096; block_size <= MAX_BLOCK_SIZE;
	    block_size <<= 1) {
		printf("block size: %d\n", block_size);

		run(fd, &fs, 1, block_size);
		run(fd, &fs, block_size, block_size);
	}
}