simoop.c

/*
 * simoop.c
 *
 * Copyright (C) 2016 Facebook
 * Chris Mason <clm@fb.com>
 *
 * GPLv2, portions copied from the kernel and from Jens Axboe's fio
 */
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <errno.h>
#include <getopt.h>
#include <sys/time.h>
#include <time.h>
#include <string.h>
#include <linux/futex.h>
#include <sys/syscall.h>
#include <sys/mman.h>
#include <libgen.h>
#include <locale.h>

/* these are part of the histogram accounting */
#define PLAT_BITS	8
#define PLAT_VAL	(1 << PLAT_BITS)
#define PLAT_GROUP_NR	19
#define PLAT_NR		(PLAT_GROUP_NR * PLAT_VAL)
#define PLAT_LIST_MAX	20

/* how deep a directory chain to make */
#define DIR_LEVEL 64

/* buffer size for reads and writes */
#define BUF_SIZE 65536

/*
 * we make a few different kinds of files, these are appended onto the
 * file name to separate them
 */
#define DATA_FILE NULL
#define RESULT_FILE "extra"
#define TMP_FILE "tmp"

/* each path in the paths array gets a thread pool hammering on it. */
char **paths;
int total_paths = 0;

/* -t  number of workers thread */
static int worker_threads = 16;
/* -r  seconds */
static int runtime = 30;
/* -c  usec */
static unsigned long long cputime = 3000000;
/* -f size of the files we create */
static unsigned long long file_size = 64 * 1024 * 1024;
/* -n number of files we create */
static unsigned long num_files = 65536;
/* -R read size */
static unsigned long read_size = 2 * 1024 * 1024;
/* -W write size */
static unsigned long write_size = 2 * 1024 * 1024;
/* -T number of files to read */
static int rw_threads = 8;
/* -D number of threads running du */
static int du_threads = 1;
/* memory to allocate and use during each task */
static int thinking_mem = 128 * 1024 * 1024;
/* should we do a truncate and fsync after every write */
static int funksync = 0;

/* -M how much memory we allocate to benchmark allocations */
static int mmap_size = 64 * 1024 * 1024;

/* these do nothing but spin */
static int cpu_threads = 24;

/* how long we sleep while processing requests */
static int sleeptime = 10000;

/*
 * after warmup_seconds, we reset the counters to get rid of noise from
 * early in the run
 */
static int warmup_seconds = 60;

/* reporting interval */
static int interval_seconds = 120;

/* the master thread flips this to true when runtime is up */
static volatile unsigned long stopping = 0;
static volatile unsigned long warmup_done = 0;

/*
 * one stat struct per thread data, when the workers sleep this records the
 * latency between when they are woken up and when they actually get the
 * CPU again.  The message threads sum up the stats of all the workers and
 * then bubble them up to main() for printing
 */
struct stats {
	unsigned int plat[PLAT_NR];
	unsigned int nr_samples;
	unsigned int max;
	unsigned int min;
};

/* this defines which latency profiles get printed */
#define PLIST_P99 2
#define PLIST_P95 1
#define PLIST_P50 0
static double plist[PLAT_LIST_MAX] = { 50.0, 95.0, 99.0, };

enum {
	HELP_LONG_OPT = 1,
};

/* this enum needs to match up with the labels array below */
enum {
	READ_STATS = 0,
	WRITE_STATS,
	ALLOC_STATS,
	TOTAL_STATS,
};

char *stat_labels[] = {
	"Read latency",
	"Write latency",
	"Allocation latency",
	NULL,
};

char *option_string = "t:s:C:c:r:n:f:FR:T:m:W:M:w:i:D:";
static struct option long_options[] = {
	{"mmapsize", required_argument, 0, 'M'},
	{"filesize", required_argument, 0, 'f'},
	{"numfiles", required_argument, 0, 'n'},
	{"readsize", required_argument, 0, 'R'},
	{"writesize", required_argument, 0, 'W'},
	{"readthreads", required_argument, 0, 'T'},
	{"duthreads", required_argument, 0, 'D'},
	{"threads", required_argument, 0, 't'},
	{"runtime", required_argument, 0, 'r'},
	{"warmuptime", required_argument, 0, 'w'},
	{"sleeptime", required_argument, 0, 's'},
	{"interval", required_argument, 0, 'i'},
	{"cputime", required_argument, 0, 'c'},
	{"cputhreads", required_argument, 0, 'C'},
	{"memory", required_argument, 0, 'm'},
	{"funksync", no_argument, 0, 'F'},
	{"help", no_argument, 0, HELP_LONG_OPT},
	{0, 0, 0, 0}
};

static void print_usage(void)
{
	fprintf(stderr, "simoop usage:\n"
		"\t-t (--threads): worker threads (def: 16)\n"
		"\t-m (--memory): memory in MB to allocate during think time in each worker (def 128)\n"
		"\t-M (--mmapsize): amount in MB to mmap to time allocator (64MB)\n"
		"\t-r (--runtime): How long to run before exiting (seconds, def: 30)\n"
		"\t-w (--warmuptime): How long to warmup before resetting the stats (seconds, def: 60)\n"
		"\t-i (--interval): Sleep time in seconds between latency reports (sec, def: 120\n"
		"\t-s (--sleeptime): Sleep time in usecs between worker loops (usec, def: 10000\n"
		"\t-c (--cputime): How long to think during each worker loop (seconds, def: 3)\n"
		"\t-C (--cputhreads): How many threads do the cpu time loop (24)\n"
		"\t-n (--numfiles): Number of files per directory tree (65536)\n"
		"\t-f (--filesize): Size of each file in MB (64MB)\n"
		"\t-R (--readsize): amount in MB to read from each file (2MB)\n"
		"\t-W (--writesize): amount in MB to write to tmp files (2MB)\n"
		"\t-T (--rwthreads): how many threads to read/write (8)\n"
		"\t-D (--duthraeds): how many threads to scanning the working dirs (1)\n"
		"\t-F (--funksync): should we fsync;truncate(0);fsync after writes\n"
		"\t dir1 [dir2 ... dirN]\n"
	       );
	exit(1);
}

static void parse_options(int ac, char **av)
{
	int c;
	int found_sleeptime = -1;
	int found_cputime = -1;
	int i;

	while (1) {
		int option_index = 0;

		c = getopt_long(ac, av, option_string,
				long_options, &option_index);

		if (c == -1)
			break;

		switch(c) {
		case 's':
			found_sleeptime = atoi(optarg);
			break;
		case 'm':
			thinking_mem = atoi(optarg);
			thinking_mem *= 1024 *1024;
			break;
		case 'M':
			mmap_size = atoi(optarg);
			mmap_size *= 1024 *1024;
			break;
		case 'c':
			found_cputime = atoi(optarg);
			break;
		case 'C':
			cpu_threads = atoi(optarg);
			break;
		case 't':
			worker_threads = atoi(optarg);
			break;
		case 'r':
			runtime = atoi(optarg);
			break;
		case 'w':
			warmup_seconds = atoi(optarg);
			break;
		case 'i':
			interval_seconds = atoi(optarg);
			break;
		case 'F':
			funksync = 0;
			break;
		case 'f':
			file_size = atoi(optarg);
			file_size *= 1024 * 1024;
			break;
		case 'n':
			num_files = atoi(optarg);
			break;
		case 'R':
			read_size = atoi(optarg);
			read_size *= 1024 * 1024;
			break;
		case 'W':
			write_size = atoi(optarg);
			write_size *= 1024 * 1024;
			break;
		case 'T':
			rw_threads = atoi(optarg);
			break;
		case 'D':
			du_threads = atoi(optarg);
			break;
		case '?':
		case HELP_LONG_OPT:
			print_usage();
			break;
		default:
			break;
		}
	}


	total_paths = ac - optind;

	if (total_paths <= 0) {
		fprintf(stderr, "No directories specified\n");
		print_usage();
		exit(1);
	}
	paths = malloc(sizeof(char *) * total_paths + 1);
	paths[total_paths] = NULL;
	for (i = 0; i < total_paths; i++) {
		paths[i] = strdup(av[optind++]);
		fprintf(stderr, "adding path %s\n", paths[i]);
	}

	/*
	 * by default pipe mode zeros out cputime and sleep time.  This
	 * sets them to any args that were actually passed in
	 */
	if (found_sleeptime >= 0)
		sleeptime = found_sleeptime;
	if (found_cputime >= 0)
		cputime = found_cputime * 1000000;

	if (optind < ac) {
		fprintf(stderr, "Error Extra arguments '%s'\n", av[optind]);
		exit(1);
	}
}

void tvsub(struct timeval * tdiff, struct timeval * t1, struct timeval * t0)
{
	tdiff->tv_sec = t1->tv_sec - t0->tv_sec;
	tdiff->tv_usec = t1->tv_usec - t0->tv_usec;
	if (tdiff->tv_usec < 0 && tdiff->tv_sec > 0) {
		tdiff->tv_sec--;
		tdiff->tv_usec += 1000000;
		if (tdiff->tv_usec < 0) {
			fprintf(stderr, "lat_fs: tvsub shows test time ran backwards!\n");
			exit(1);
		}
	}

	/* time shouldn't go backwards!!! */
	if (tdiff->tv_usec < 0 || t1->tv_sec < t0->tv_sec) {
		tdiff->tv_sec = 0;
		tdiff->tv_usec = 0;
	}
}

/*
 * returns the difference between start and stop in usecs.  Negative values
 * are turned into 0
 */
unsigned long long tvdelta(struct timeval *start, struct timeval *stop)
{
	struct timeval td;
	unsigned long long usecs;

	tvsub(&td, stop, start);
	usecs = td.tv_sec;
	usecs *= 1000000;
	usecs += td.tv_usec;
	return (usecs);
}

/* mr axboe's magic latency histogram */
static unsigned int plat_val_to_idx(unsigned int val)
{
	unsigned int msb, error_bits, base, offset;

	/* Find MSB starting from bit 0 */
	if (val == 0)
		msb = 0;
	else
		msb = sizeof(val)*8 - __builtin_clz(val) - 1;

	/*
	 * MSB <= (PLAT_BITS-1), cannot be rounded off. Use
	 * all bits of the sample as index
	 */
	if (msb <= PLAT_BITS)
		return val;

	/* Compute the number of error bits to discard*/
	error_bits = msb - PLAT_BITS;

	/* Compute the number of buckets before the group */
	base = (error_bits + 1) << PLAT_BITS;

	/*
	 * Discard the error bits and apply the mask to find the
	 * index for the buckets in the group
	 */
	offset = (PLAT_VAL - 1) & (val >> error_bits);

	/* Make sure the index does not exceed (array size - 1) */
	return (base + offset) < (PLAT_NR - 1) ?
		(base + offset) : (PLAT_NR - 1);
}

/*
 * Convert the given index of the bucket array to the value
 * represented by the bucket
 */
static unsigned int plat_idx_to_val(unsigned int idx)
{
	unsigned int error_bits, k, base;

	if (idx >= PLAT_NR) {
		fprintf(stderr, "idx %u is too large\n", idx);
		exit(1);
	}

	/* MSB <= (PLAT_BITS-1), cannot be rounded off. Use
	 * all bits of the sample as index */
	if (idx < (PLAT_VAL << 1))
		return idx;

	/* Find the group and compute the minimum value of that group */
	error_bits = (idx >> PLAT_BITS) - 1;
	base = 1 << (error_bits + PLAT_BITS);

	/* Find its bucket number of the group */
	k = idx % PLAT_VAL;

	/* Return the mean of the range of the bucket */
	return base + ((k + 0.5) * (1 << error_bits));
}


static unsigned int calc_percentiles(unsigned int *io_u_plat, unsigned long nr,
				     unsigned int **output)
{
	unsigned long sum = 0;
	unsigned int len, i, j = 0;
	unsigned int oval_len = 0;
	unsigned int *ovals = NULL;
	int is_last;

	len = 0;
	while (len < PLAT_LIST_MAX && plist[len] != 0.0)
		len++;

	if (!len)
		return 0;

	/*
	 * Calculate bucket values, note down max and min values
	 */
	is_last = 0;
	for (i = 0; i < PLAT_NR && !is_last; i++) {
		sum += io_u_plat[i];
		while (sum >= (plist[j] / 100.0 * nr)) {
			if (j == oval_len) {
				oval_len += 100;
				ovals = realloc(ovals, oval_len * sizeof(unsigned int));
			}

			ovals[j] = plat_idx_to_val(i);
			is_last = (j == len - 1);
			if (is_last)
				break;

			j++;
		}
	}

	*output = ovals;
	return len;
}

static void calc_p99(struct stats *s, unsigned int *p50,
		     unsigned int *p95, unsigned int *p99)
{
	unsigned int *ovals = NULL;
	int len;

	*p50 = 0;
	*p95 = 0;
	*p99 = 0;
	len = calc_percentiles(s->plat, s->nr_samples, &ovals);
	if (len && len > PLIST_P99)
		*p99 = ovals[PLIST_P99];
	if (len && len > PLIST_P99)
		*p95 = ovals[PLIST_P95];
	if (len && len > PLIST_P50)
		*p50 = ovals[PLIST_P50];
	if (ovals)
		free(ovals);
}

/* fold latency info from s into d */
void combine_stats(struct stats *d, struct stats *s)
{
	int i;
	for (i = 0; i < PLAT_NR; i++)
		d->plat[i] += s->plat[i];
	d->nr_samples += s->nr_samples;
	if (s->max > d->max)
		d->max = s->max;
	if (s->min < d->min)
		d->min = s->min;
}

/* record a latency result into the histogram */
static void add_lat(struct stats *s, unsigned int us)
{
	int lat_index = 0;

	if (us > s->max)
		s->max = us;
	if (us < s->min)
		s->min = us;

	lat_index = plat_val_to_idx(us);
	__sync_fetch_and_add(&s->plat[lat_index], 1);
	__sync_fetch_and_add(&s->nr_samples, 1);
}

/*
 * every thread has one of these, it comes out to about 19K thanks to the
 * giant stats struct
 */
struct thread_data {
	pthread_t tid;
	/* per-thread count of worker loops over the life of the run */
	unsigned long long work_done;
	char *read_buf;
	char *write_buf;
	/* latency histogram */
	struct stats stats[TOTAL_STATS];
};

#define nop __asm__ __volatile__("rep;nop": : :"memory")
static void usec_spin(unsigned long spin_time)
{
	struct timeval now;
	struct timeval start;
	unsigned long long delta;

	if (spin_time == 0)
		return;

	gettimeofday(&start, NULL);
	while (1) {
		gettimeofday(&now, NULL);
		delta = tvdelta(&start, &now);
		if (delta > spin_time)
			return;
		nop;
	}
}

/*
 * runs during initial file creation to create one dir
 * in the tree
 */
static void make_one_dir(char *path, int a, int b)
{
	char subdir[256];
	int ret;

	if (b >= 0)
		ret = snprintf(subdir, 256, "%s/%d/%d", path, a, b);
	else
		ret = snprintf(subdir, 256, "%s/%d", path, a);

	if (ret >= 256 || ret < 0) {
		perror("file name too long\n");
		exit(1);
	}
	ret = mkdir(subdir, 0700);
	if (ret && errno != EEXIST) {
		perror("mkdir");
		exit(1);
	}
}


/* create the subdir tree (no files) */
static void make_dirs(char *path)
{
	int first;
	int second;

	for (first = 0; first < 64; first++) {
		make_one_dir(path, first, -1);
		for (second = 0; second < 64; second++) {
			make_one_dir(path, first, second);
		}
	}
}

/*
 * helper to form pathnames, if postfix isn't NULL, it'll be tossed
 * onto the end of the filename
 */
static void join_path(char *name, char *path, int seq, char *postfix)
{
	int a;
	int b;
	int ret;

	a = seq % DIR_LEVEL;
	b = (seq / DIR_LEVEL) % DIR_LEVEL;

	if (postfix)
		ret = snprintf(name, 256, "%s/%d/%d/%d-%s", path, a, b, seq, postfix);
	else
		ret = snprintf(name, 256, "%s/%d/%d/%d", path, a, b, seq);

	if (ret >= 256 || ret < 0) {
		perror("file name too long\n");
		exit(1);
	}
}

/* unlink working files not part of the main dataset for a given filename. */
static void unlink_extra(char *path, int seq)
{
	char name[256];
	int ret;

	join_path(name, path, seq, RESULT_FILE);
	ret = unlink(name);
	if (ret < 0 && errno != ENOENT) {
		perror("unlink");
		exit(1);
	}
	join_path(name, path, seq, TMP_FILE);
	ret = unlink(name);
	if (ret < 0 && errno != ENOENT) {
		perror("unlink");
		exit(1);
	}
}

/* construct a filename and return the fd */
static int open_path(char *path, int seq, char *postfix, int flags)
{
	int fd;
	char name[256];

	join_path(name, path, seq, postfix);
	fd = open(name, O_RDWR | O_CREAT | flags, 0600);
	if (fd < 0) {
		perror("open");
		exit(1);
	}
	return fd;
}

/* helper for startup, do initial writes to a given fd */
static void fill_one_file(int fd)
{
	struct stat st;
	int ret;
	unsigned long long cur_size;
	char *buf;

	ret = fstat(fd, &st);
	if (ret < 0) {
		perror("stat");
		exit(1);
	}
	cur_size = st.st_size;

	if (cur_size >= file_size)
		return;

	buf = malloc(BUF_SIZE);
	if (!buf) {
		perror("malloc");
		exit(1);
	}


	memset(buf, 'a', BUF_SIZE);
	while (cur_size < file_size) {
		ret = write(fd, buf, BUF_SIZE);
		if (ret < 0) {
			perror("write");
			exit(1);
		}
		if (ret < BUF_SIZE) {
			fprintf(stderr, "short write\n");
			exit(1);
		}
		cur_size += ret;
	}

	free(buf);
}

/*
 * The du thread runs every so often and stats every single file in a
 * given path.  This puts a lot of stress on the slab caches, and at
 * least for XFS sets a bunch of radix bits used to track which allocation
 * groups need to have their inodes cleaned.  It creates stress inside
 * the shrinker.
 */
static void *du_thread(void *arg)
{
	unsigned long seq;
	char *path = arg;
	struct stat st;
	int fd;
	int ret;

	while (!stopping) {
		fprintf(stderr, "du thread is running %s\n", path);
		for (seq = 0; seq < num_files; seq++) {
			fd = open_path(path, seq, DATA_FILE, 0);
			ret = fstat(fd, &st);
			if (ret < 0 && errno != ENOENT) {
				perror("fstat");
				exit(1);
			}
			close(fd);
		}
		fprintf(stderr, "du thread is done %s\n", path);

		/*
		 * we need some jitter in here so all the du threads are
		 * staggered
		 */
		sleep(45 + (rand() % 90));
	}
	return NULL;
}

/*
 * create a temporary file and dirty it
 */
static void dirty_an_inode(char *path)
{
	int fd;
	int seq = rand() % num_files;

	fd = open_path(path, seq, TMP_FILE, 0);
	ftruncate(fd, 100);
	ftruncate(fd, 0);
	close(fd);
}

static void record_one_lat(struct stats *stat, struct timeval *start,
			   struct timeval *finish)
{
	unsigned long long delta;

	delta = tvdelta(start, finish);
	if (delta > 0)
		add_lat(stat, delta);

}

/* reads from a random (well aligned) offset in one of the main data files */
static void read_from_file(char *path, int seq, char *buf)
{
	int fd;
	int ret;
	int i;
	unsigned long read_bytes = read_size;
	unsigned long long offset;

	if (read_bytes > file_size)
		read_bytes = file_size;

	/* pick a random MB starting point */
	offset = rand() % (file_size / (1024 * 1024));
	offset *= 1024 * 1024;
	if (offset + read_bytes > file_size)
		offset = file_size - read_bytes;

	fd = open_path(path, seq, DATA_FILE, 0);

	while (read_bytes > 0) {
		ret = pread(fd, buf, BUF_SIZE, offset);
		if (ret == 0)
			break;
		if (ret < 0) {
			fprintf(stderr, "bad read %s seq %d ret %d offset %Lu\n", path, seq, ret, offset);
			perror("read");
			exit(1);
		}
		offset += ret;
		read_bytes -= ret;
	}

	/* if we don't have writers making dirty inodes, make some here */
	if (!write_size) {
		for (i = 0; i < 8; i++)
			dirty_an_inode(path);
	}
	close(fd);
}

/* creates a temp file in one of the subdirs and sends down write_bytes to it */
static void write_to_file(char *path, int seq, char *buf)
{
	int fd;
	int ret;
	int i;
	unsigned long write_bytes = write_size;
	unsigned long long offset = 0;

	fd = open_path(path, seq, RESULT_FILE, 0);

	while (write_bytes > 0) {
		ret = write(fd, buf, BUF_SIZE);
		if (ret == 0)
			break;
		if (ret < 0) {
			fprintf(stderr, "bad write %s seq %d ret %d offset %Lu\n", path, seq, ret, offset);
			perror("write");
			exit(1);
		}
		offset += ret;
		write_bytes -= ret;
	}
	if (funksync) {
		fsync(fd);
		ftruncate(fd, 0);
		fsync(fd);
	}
	close(fd);

	/* make some dirty inodes */
	for (i = 0; i < 8; i++)
		dirty_an_inode(path);
}

/* make all the worker files under a main path */
static void make_files(char *path)
{
	unsigned long seq;
	int fd;

	for (seq = 0; seq < num_files; seq++) {
		fd = open_path(path, seq, DATA_FILE, 0);
		fill_one_file(fd);
		close(fd);

		/* cleanup from the last run */
		unlink_extra(path, seq);
	}
}

void *filler_thread(void *arg)
{
	char *path = arg;
	make_dirs(path);
	make_files(path);
	return 0;
}

/* start one thread per path, create the directory tree */
void run_filler_threads(void)
{
	int i;
	int ret;
	pthread_t *tids;

	tids = malloc(sizeof(*tids) * total_paths);
	if (!tids) {
		perror("malloc");
		exit(1);
	}
	fprintf(stderr, "Creating working files\n");
	for (i = 0; i < total_paths; i++) {
		pthread_t tid;
		ret = pthread_create(&tid, NULL, filler_thread,
				     paths[i]);
		if (ret) {
			fprintf(stderr, "error %d from pthread_create\n", ret);
			exit(1);
		}
		tids[i] = tid;
	}
	for (i = 0; i < total_paths; i++) {
		pthread_join(tids[i], NULL);
	}
	fprintf(stderr, "done creating working files\n");
	free(tids);
}

void *read_thread(void *arg)
{
	int index = rand() % total_paths;
	int seq = rand() % num_files;
	char *path = paths[index];
	char *buf = arg;

	read_from_file(path, seq, buf);
	return NULL;
}

/* startup reader threads, returns the tids for later waiting */
void read_some_files(char *buf, pthread_t *tids)
{
	int i;
	int ret;

	for (i = 0; i < rw_threads; i++) {
		pthread_t tid;
		ret = pthread_create(&tid, NULL, read_thread,
				     buf + i * read_size);
		if (ret) {
			fprintf(stderr, "error %d from pthread_create\n", ret);
			exit(1);
		}
		tids[i] = tid;
	}
}

void *write_thread(void *arg)
{
	int index = rand() % total_paths;
	int seq = rand() % num_files;
	char *path = paths[index];
	char *buf = arg;

	write_to_file(path, seq, buf);
	return NULL;
}

/* startup writer threads, returns the tids for later waiting */
void write_some_files(char *buf, pthread_t *tids)
{
	int i;
	int ret;

	for (i = 0; i < rw_threads; i++) {
		pthread_t tid;
		ret = pthread_create(&tid, NULL, write_thread,
				     buf + i * write_size);
		if (ret) {
			fprintf(stderr, "error %d from pthread_create\n", ret);
			exit(1);
		}
		tids[i] = tid;
	}
}

/* main work loop */
void *worker_thread(void *arg)
{
	struct timeval now;
	struct timeval start;
	struct thread_data *td = arg;
	char *read_buf;
	char *write_buf;
	char *mem = NULL;
	pthread_t *read_tids;
	pthread_t *write_tids;
	char *mmap_ptr;
	int i;
	int warmup_zerod = 0;

	read_tids = malloc(sizeof(*read_tids) * rw_threads);
	write_tids = malloc(sizeof(*write_tids) * rw_threads);
	mem = malloc(thinking_mem);

	if (!read_tids || !write_tids || !mem) {
		perror("allocation failed\n");
		exit(1);
	}

	while(!stopping) {
		/*
		 * reset our stats after warmup so we don't have noise
		 * from initial thread creation
		 */
		if (warmup_done && !warmup_zerod) {
			memset(td->stats, 0, sizeof(*td->stats) * TOTAL_STATS);
			warmup_zerod = 1;
		}
		read_buf = malloc(rw_threads * read_size);
		write_buf = malloc(rw_threads * write_size);

		if (!read_buf || !write_buf) {
			perror("allocation");
			exit(1);
		}

		/* if someone swapped out our thinking mem, bring it back */
		memset(mem, 0, thinking_mem);

		gettimeofday(&start, NULL);

		/* Start the threads to read files */
		read_some_files(read_buf, read_tids);

		/* think in parallel */
		usec_spin(cputime);

		/* wait for our reads to finish */
		for (i = 0; i < rw_threads; i++) {
			pthread_join(read_tids[i], NULL);
		}
		gettimeofday(&now, NULL);

		/*
		 * record how long the reading stage took.  This
		 * includes all of the latencies for thread creation,
		 * doing the reads and waiting for completeion
		 */
		record_one_lat(&td->stats[READ_STATS], &start, &now);

		/* write out the (pretend) results */
		if (write_size) {
			gettimeofday(&start, NULL);
			write_some_files(write_buf, write_tids);
			for (i = 0; i < rw_threads; i++) {
				pthread_join(write_tids[i], NULL);
			}
			gettimeofday(&now, NULL);
			record_one_lat(&td->stats[WRITE_STATS], &start, &now);
		}

		/*
		 * we also track the latency to allocate and fault in
		 * a chunk of pages.  This is basicaly the user-visible
		 * impact of allocation stalls
		 */
		gettimeofday(&start, NULL);

		mmap_ptr = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE,
				MAP_ANONYMOUS | MAP_PRIVATE,
				-1, 0);

		if (mmap_ptr == MAP_FAILED) {
			perror("mmap");
			exit(1);
		}

		/* fault in all those pages */
		for (i = 0; i < mmap_size; i += 4096) {
			mmap_ptr[i] = 'a';
		}

		/* measure how long all of this took */
		gettimeofday(&now, NULL);
		record_one_lat(&td->stats[ALLOC_STATS], &start, &now);

		/* think again, pretending we've done something useful */
		munmap(mmap_ptr, mmap_size);
		usec_spin(cputime);
		free(read_buf);
		free(write_buf);

		td->work_done++;

		usleep(sleeptime);
	}

	free(mem);
	free(read_tids);
	free(write_tids);
	return NULL;
}

/*
 * we want to keep the CPUs saturated so kswapd has to compete for CPU time
 * these cpu threads don't do IO.
 */
static void *cpu_thread(void *arg)
{
	char *unused = arg;
	arg = unused;
	while(!stopping) {
		usec_spin(cputime);
		usleep(1);
	}
	return NULL;
}

/*
 * read in /proc/vmstat so we can sum the allocation stall lines and
 * print them out
 */
static int read_allocstalls(void)
{
	int stalls = 0;
	int val;
	FILE * fp;
	char * line = NULL;
	size_t len = 0;
	ssize_t read;

	fp = fopen("/proc/vmstat", "r");
	if (fp == NULL)
		return 0;

	while ((read = getline(&line, &len, fp)) != -1) {
		/*
		 * newer kernels break out different types of allocstall,
		 * just add them all together
		 */
		if (strstr(line, "allocstall")) {
			char *p = strchr(line, ' ');
			if (p && p[1] != '\0') {
				val = atoi(p + 1);
				stalls += val;
			}
		}
	}

	if (line)
		free(line);
	fclose(fp);
	return stalls;
}

/*
 * every worker thread tracks latencies individually.  This pulls them all
 * into a single destination stat array for printing
 */
static void collect_stats(struct stats *dest, struct thread_data *worker_threads_mem)
{
	int i;
	int j;

	memset(dest, 0, sizeof(*dest) * TOTAL_STATS);
	for (i = 0; i < TOTAL_STATS; i++) {
		for (j = 0; j < worker_threads; j++)
			combine_stats(&dest[i], &worker_threads_mem[j].stats[i]);
	}
	for (i = 0; i < TOTAL_STATS; i++) {
		unsigned int p50 = 0, p95 = 0, p99 = 0;
		calc_p99(&dest[i], &p50, &p95, &p99);
		printf("%s (p50: %'d) (p95: %'d) (p99: %'d)\n",
		       stat_labels[i], p50, p95, p99);
	}
}

/*
 * print out the current stats, along with averages and latency histogram
 * numbers
 */
static void print_latencies(struct thread_data *worker_threads_mem,
			    struct stats *stats,
			    struct stats *work_done_stats,
			    struct stats *allocstall_stats,
			    double work_done, double instant_work_done,
			    double allocstalls,
			    double instant_allocstalls,
			    unsigned long long delta,
			    unsigned long long instant_delta)
{
	double rate;
	double instant_rate;
	double seconds = (double)delta / 1000000;
	unsigned int p50, p95, p99;

	printf("___\n");
	printf("Run time: %.0f seconds\n", seconds);

	/* this also prints the histogram results from the workers */
	collect_stats(stats, worker_threads_mem);

	/* calculate the work done over this period, add to histogram */
	rate = (work_done * 1000000) / delta;
	instant_rate = (instant_work_done * 1000000) / instant_delta;
	add_lat(work_done_stats, rate * 100);
	calc_p99(work_done_stats, &p50, &p95, &p99);

	printf("work rate = %.2f/sec (avg %.2f/sec) (p50: %.2f) (p95: %.2f) (p99: %.2f)\n",
	       instant_rate, rate, (double)p50/100.00, (double)p95/100.00, (double)p99/100.00);

	/* do the same for the allocation stall rate */
	rate = (allocstalls * 1000000) / delta;
	instant_rate = (instant_allocstalls * 1000000) / instant_delta;
	add_lat(allocstall_stats, rate * 100);
	calc_p99(allocstall_stats, &p50, &p95, &p99);
	printf("alloc stall rate = %.2f/sec (avg: %.2f) (p50: %.2f) (p95: %.2f) (p99: %.2f)\n",
	       instant_rate, rate, (double)p50/100.00, (double)p95/100.00, (double)p99/100.00);

}

/* runtime from the command line is in seconds.  Sleep until its up */
static void sleep_for_runtime(struct thread_data *worker_threads_mem)
{
	struct timeval now;
	struct timeval start;
	struct timeval rate_start;
	struct timeval instant_start;
	unsigned long long delta;
	unsigned long long rate_delta;
	unsigned long long instant_delta;
	unsigned long long runtime_usec = runtime * 1000000;
	unsigned long long warmup_usec = warmup_seconds * 1000000;
	double work_done = 0;
	double instant_work_done = 0;
	double last_work_done = 0;
	double allocstalls = 0;
	double instant_allocstalls = 0;
	double last_allocstalls = 0;
	struct stats stats[TOTAL_STATS];
	struct stats work_done_stats;
	struct stats allocstall_stats;
	int i;

	gettimeofday(&start, NULL);
	rate_start = start;

	memset(&work_done_stats, 0, sizeof(work_done_stats));
	memset(&allocstall_stats, 0, sizeof(allocstall_stats));

	last_allocstalls = read_allocstalls();
	allocstalls = last_allocstalls;
	while(1) {
		gettimeofday(&now, NULL);
		instant_start = now;
		delta = tvdelta(&start, &now);

		if (!warmup_done && delta > warmup_usec) {
			printf("Warmup complete (%d seconds)\n", warmup_seconds);
			__sync_synchronize();
			warmup_done = 1;
			memset(&work_done_stats, 0, sizeof(work_done_stats));
			memset(&allocstall_stats, 0, sizeof(allocstall_stats));
			last_allocstalls = read_allocstalls();
			last_work_done = work_done;
			rate_start = now;
		}

		instant_allocstalls = allocstalls;
		instant_work_done = work_done;
		if (delta < runtime_usec)
			sleep(interval_seconds);
		else
			break;

		gettimeofday(&now, NULL);
		rate_delta = tvdelta(&rate_start, &now);
		instant_delta = tvdelta(&instant_start, &now);

		work_done = 0;
		for (i = 0; i < worker_threads; i++)
			work_done += worker_threads_mem[i].work_done;

		allocstalls = read_allocstalls();
		if (allocstalls < last_allocstalls)
			allocstalls = last_allocstalls;

		print_latencies(worker_threads_mem, stats,
				&work_done_stats,
				&allocstall_stats,
				work_done - last_work_done,
				work_done - instant_work_done,
				allocstalls - last_allocstalls,
				allocstalls - instant_allocstalls,
				rate_delta, instant_delta);

	}
	__sync_synchronize();
	stopping = 1;

	for (i = 0; i < cpu_threads; i++) {
		pthread_join(worker_threads_mem[i + worker_threads].tid, NULL);
	}

	work_done = 0;
	for (i = 0; i < worker_threads; i++)
		work_done += worker_threads_mem[i].work_done;

	gettimeofday(&now, NULL);
	rate_delta = tvdelta(&rate_start, &now);
	instant_delta = tvdelta(&instant_start, &now);
	print_latencies(worker_threads_mem, stats,
			&work_done_stats,
			&allocstall_stats,
			work_done - last_work_done,
			work_done - instant_work_done,
			allocstalls - last_allocstalls,
			allocstalls - instant_allocstalls,
			rate_delta, instant_delta);

}

int main(int ac, char **av)
{
	int i;
	int ret;
	int index;
	struct thread_data *worker_threads_mem = NULL;
	pthread_t *du_tids;

	setlocale(LC_NUMERIC, "");
	parse_options(ac, av);

	if (du_threads > total_paths)
		du_threads = total_paths;
	du_tids = calloc(du_threads, sizeof(pthread_t));

	worker_threads_mem = calloc(worker_threads + cpu_threads,
				    sizeof(struct thread_data));
	if (!worker_threads_mem || !du_tids) {
		perror("calloc");
		exit(1);
	}

	/* fill up our directory tree.  This might take a really long time */
	run_filler_threads();

	stopping = 0;

	/* worker threads do the IO and the real stuff */
	for (i = 0; i < worker_threads; i++) {
		pthread_t tid;
		ret = pthread_create(&tid, NULL, worker_thread,
				     worker_threads_mem + i);
		if (ret) {
			perror("pthread_create");
			exit(1);
		}
		worker_threads_mem[i].tid = tid;
	}

	/* CPU threads just soak up cycles */
	for (i = 0; i < cpu_threads; i++) {
		pthread_t tid;
		ret = pthread_create(&tid, NULL, cpu_thread,
				     worker_threads_mem + i + worker_threads);
		if (ret) {
			perror("pthread_create");
			exit(1);
		}
		worker_threads_mem[i + worker_threads].tid = tid;
	}

	/*
	 * du threads read in inodes, the goal is to have it happen on just
	 * a couple of paths
	 */
	index = rand();
	for (i = 0; i < du_threads; i++) {
		ret = pthread_create(&du_tids[i], NULL, du_thread,
				     paths[index++ % total_paths]);
		if (ret) {
			fprintf(stderr, "error %d from pthread_create\n", ret);
			exit(1);
		}
	}

	/* let all the magic happen and collect results */
	sleep_for_runtime(worker_threads_mem);

	for (i = 0; i < du_threads; i++) {
		pthread_join(du_tids[i], NULL);
	}

	free(worker_threads_mem);
	return 0;
}