schbench.c

/*
 * schbench.c
 *
 * Copyright (C) 2016 Facebook
 * Chris Mason <clm@fb.com>
 *
 * GPLv2, portions copied from the kernel and from Jens Axboe's fio
 *
 * gcc -Wall -O0 -W schbench.c -o schbench -lpthread
 */
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <getopt.h>
#include <sys/time.h>
#include <time.h>
#include <string.h>
#include <math.h>
#include <linux/futex.h>
#include <sys/syscall.h>

#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

/* when -p is on, how much do we send back and forth */
#define PIPE_TRANSFER_BUFFER (1 * 1024 * 1024)

#define USEC_PER_SEC (1000000)

/* -m number of message threads */
static int message_threads = 2;
/* -t  number of workers per message thread */
static int worker_threads = 16;
/* -r  seconds */
static int runtime = 30;
/* -s  usec */
static int sleeptime = 30000;
/* -C  usec */
static int message_cputime = 30000;
/* -w  seconds */
static int warmuptime = 5;
/* -i  seconds */
static int intervaltime = 10;
/* -z  seconds */
static int zerotime = 0;
/* -c  usec */
static unsigned long long cputime = 30000;
/* -f  cache_footprint_kb */
static unsigned long cache_footprint_kb = 1536;
/* -n  operations */
static unsigned long operations = 0;
/* -a, bool */
static int autobench = 0;
/* -j jitter bool */
static int jitter = 0;
/* -A, int percentage busy */
static int auto_rps = 0;
/* -p bytes */
static int pipe_test = 0;
/* -R requests per sec */
static unsigned long long requests_per_sec = 0;

/* the message threads flip this to true when they decide runtime is up */
static volatile unsigned long stopping = 0;

/* size of matrices to multiply */
static unsigned long matrix_size = 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 long nr_samples;
	unsigned int max;
	unsigned int min;
};

/* this defines which latency profiles get printed */
#define PLIST_P99 4
#define PLIST_P95 3
static double plist[PLAT_LIST_MAX] = { 50.0, 75.0, 90.0, 95.0, 99.0, 99.5, 99.9 };

enum {
	HELP_LONG_OPT = 1,
};

char *option_string = "p:am:t:s:c:C:r:R:w:i:z:A:jn:F:";
static struct option long_options[] = {
	{"auto", no_argument, 0, 'a'},
	{"jitter", no_argument, 0, 'j'},
	{"pipe", required_argument, 0, 'p'},
	{"message-threads", required_argument, 0, 'm'},
	{"threads", required_argument, 0, 't'},
	{"runtime", required_argument, 0, 'r'},
	{"rps", required_argument, 0, 'R'},
	{"auto-rps", required_argument, 0, 'A'},
	{"sleeptime", required_argument, 0, 's'},
	{"message_cputime", required_argument, 0, 'C'},
	{"cputime", required_argument, 0, 'c'},
	{"cache_footprint", required_argument, 0, 'f'},
	{"operations", required_argument, 0, 'n'},
	{"warmuptime", required_argument, 0, 'w'},
	{"intervaltime", required_argument, 0, 'i'},
	{"zerotime", required_argument, 0, 'z'},
	{"help", no_argument, 0, HELP_LONG_OPT},
	{0, 0, 0, 0}
};

static void print_usage(void)
{
	fprintf(stderr, "schbench usage:\n"
		"\t-m (--message-threads): number of message threads (def: 2)\n"
		"\t-t (--threads): worker threads per message thread (def: 16)\n"
		"\t-r (--runtime): How long to run before exiting (seconds, def: 30)\n"
		"\t-s (--sleeptime): Message thread latency (usec, def: 30000\n"
		"\t-C (--message_cputime): Message thread think time (usec, def: 30000\n"
		"\t-c (--cputime): How long to think during loop (usec, def: 30000\n"
		"\t-F (--cache_footprint): cache footprint (kb, def: 6144)\n"
		"\t-n (--operations): operations to perform (def: 0)\n"
		"\t-a (--auto): grow thread count until latencies hurt (def: off)\n"
		"\t-j (--jitter): add jitter to sleep/cputimes (def: off)\n"
		"\t-A (--auto-rps): grow RPS until cpu utilization hits target (def: none)\n"
		"\t-p (--pipe): transfer size bytes to simulate a pipe test (def: 0)\n"
		"\t-R (--rps): requests per second mode (count, def: 0)\n"
		"\t-w (--warmuptime): how long to warmup before resettings stats (seconds, def: 5)\n"
		"\t-i (--intervaltime): interval for printing latencies (seconds, def: 10)\n"
		"\t-z (--zerotime): interval for zeroing latencies (seconds, def: never)\n"
	       );
	exit(1);
}

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

	while (1) {
		int option_index = 0;

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

		if (c == -1)
			break;

		switch(c) {
		case 'a':
			autobench = 1;
			warmuptime = 0;
			break;
		case 'j':
			jitter = 1;
			break;
		case 'A':
			auto_rps = atoi(optarg);
			warmuptime = 0;
			if (requests_per_sec == 0)
				requests_per_sec = 10;
			break;
		case 'p':
			pipe_test = atoi(optarg);
			if (pipe_test > PIPE_TRANSFER_BUFFER) {
				fprintf(stderr, "pipe size too big, using %d\n",
					PIPE_TRANSFER_BUFFER);
				pipe_test = PIPE_TRANSFER_BUFFER;
			}
			sleeptime = 0;
			cputime = 0;
			warmuptime = 0;
			message_cputime = 0;
			break;
		case 's':
			found_sleeptime = atoi(optarg);
			break;
		case 'c':
			found_cputime = atoi(optarg);
			break;
		case 'C':
			found_message_cputime = atoi(optarg);
			break;
		case 'w':
			found_warmuptime = atoi(optarg);
			break;
		case 'm':
			message_threads = atoi(optarg);
			break;
		case 't':
			worker_threads = atoi(optarg);
			break;
		case 'r':
			runtime = atoi(optarg);
			break;
		case 'i':
			intervaltime = atoi(optarg);
			break;
		case 'z':
			zerotime = atoi(optarg);
			break;
		case 'R':
			requests_per_sec = atoi(optarg);
			break;
		case 'n':
			operations = atoi(optarg);
			break;
		case 'F':
			cache_footprint_kb = atoi(optarg);
			break;
		case '?':
		case HELP_LONG_OPT:
			print_usage();
			break;
		default:
			break;
		}
	}

	/*
	 * 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;
	if (found_warmuptime >= 0)
		warmuptime = found_warmuptime;
	if (found_message_cputime >= 0)
		message_cputime = message_cputime;

	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 += USEC_PER_SEC;
		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 *= USEC_PER_SEC;
	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 **output_counts)
{
	unsigned long sum = 0;
	unsigned int len, i, j = 0;
	unsigned int oval_len = 0;
	unsigned int *ovals = NULL;
	unsigned long *ocounts = NULL;
	unsigned long last = 0;
	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));
				ocounts = realloc(ocounts, oval_len * sizeof(unsigned long));
			}

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

	for (i = 1; i < len; i++) {
		last += ocounts[i - 1];
		ocounts[i] -= last;
	}
	*output = ovals;
	*output_counts = ocounts;
	return len;
}

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

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

static void show_latencies(struct stats *s, unsigned long long runtime)
{
	unsigned int *ovals = NULL;
	unsigned long *ocounts = NULL;
	unsigned int len, i;

	len = calc_percentiles(s->plat, s->nr_samples, &ovals, &ocounts);
	if (len) {
		fprintf(stderr, "Latency percentiles (usec) runtime %llu (s) (%lu total samples)\n", runtime, s->nr_samples);
		for (i = 0; i < len; i++)
			fprintf(stderr, "\t%s%2.1fth: %-10u (%lu samples)\n",
				i == PLIST_P99 ? "* " : "  ",
				plist[i], ovals[i], ocounts[i]);
	}

	if (ovals)
		free(ovals);
	if (ocounts)
		free(ocounts);

	fprintf(stderr, "\t  min=%u, max=%u\n", s->min, s->max);
}

/* 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 (d->min == 0 || 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 (!matrix_size) {
		if (us > cputime)
			us -= cputime;
		else
			us = 1;
	}

	if (us > s->max)
		s->max = us;
	if (s->min == 0 || 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);
}

struct request {
	struct timeval start_time;
	struct request *next;
};

/*
 * every thread has one of these, it comes out to about 19K thanks to the
 * giant stats struct
 */
struct thread_data {
	pthread_t tid;
	/* ->next is for placing us on the msg_thread's list for waking */
	struct thread_data *next;

	/* ->request is all of our pending request */
	struct request *request;

	/* our parent thread and messaging partner */
	struct thread_data *msg_thread;

	/*
	 * the msg thread stuffs gtod in here before waking us, so we can
	 * measure scheduler latency
	 */
	struct timeval wake_time;

	/* keep the futex and the wake_time in the same cacheline */
	int futex;

	/* mr axboe's magic latency histogram */
	struct stats stats;
	unsigned long long loop_count;
	unsigned long long runtime;
	unsigned long pending;

	char pipe_page[PIPE_TRANSFER_BUFFER];

	/* matrices to multiply */
	unsigned long *data;
};

/* we're so fancy we make our own futex wrappers */
#define FUTEX_BLOCKED 0
#define FUTEX_RUNNING 1

static int futex(int *uaddr, int futex_op, int val,
		 const struct timespec *timeout, int *uaddr2, int val3)
{
	return syscall(SYS_futex, uaddr, futex_op, val, timeout, uaddr2, val3);
}

/*
 * wakeup a process waiting on a futex, making sure they are really waiting
 * first
 */
static void fpost(int *futexp)
{
	int s;

	if (__sync_bool_compare_and_swap(futexp, FUTEX_BLOCKED,
					 FUTEX_RUNNING)) {
		s = futex(futexp, FUTEX_WAKE_PRIVATE, 1, NULL, NULL, 0);
		if (s  == -1) {
			perror("FUTEX_WAKE");
			exit(1);
		}
	}
}

/*
 * wait on a futex, with an optional timeout.  Make sure to set
 * the futex to FUTEX_BLOCKED beforehand.
 *
 * This will return zero if all went well, or return -ETIMEDOUT if you
 * hit the timeout without getting posted
 */
static int fwait(int *futexp, struct timespec *timeout)
{
	int s;
	while (1) {
		/* Is the futex available? */
		if (__sync_bool_compare_and_swap(futexp, FUTEX_RUNNING,
						 FUTEX_BLOCKED)) {
			break;      /* Yes */
		}
		/* Futex is not available; wait */
		s = futex(futexp, FUTEX_WAIT_PRIVATE, FUTEX_BLOCKED, timeout, NULL, 0);
		if (s == -1 && errno != EAGAIN) {
			if (errno == ETIMEDOUT)
				return -ETIMEDOUT;
			perror("futex-FUTEX_WAIT");
			exit(1);
		}
	}
	return 0;
}

/*
 * cmpxchg based list prepend
 */
static void xlist_add(struct thread_data *head, struct thread_data *add)
{
	struct thread_data *old;
	struct thread_data *ret;

	while (1) {
		old = head->next;
		add->next = old;
		ret = __sync_val_compare_and_swap(&head->next, old, add);
		if (ret == old)
			break;
	}
}

/*
 * xchg based list splicing.  This returns the entire list and
 * replaces the head->next with NULL
 */
static struct thread_data *xlist_splice(struct thread_data *head)
{
	struct thread_data *old;
	struct thread_data *ret;

	while (1) {
		old = head->next;
		ret = __sync_val_compare_and_swap(&head->next, old, NULL);
		if (ret == old)
			break;
	}
	return ret;
}

/*
 * cmpxchg based list prepend
 */
static struct request *request_add(struct thread_data *head, struct request *add)
{
	struct request *old;
	struct request *ret;

	while (1) {
		old = head->request;
		add->next = old;
		ret = __sync_val_compare_and_swap(&head->request, old, add);
		if (ret == old)
			return old;
	}
}

/*
 * xchg based list splicing.  This returns the entire list and
 * replaces the head->request with NULL.  The list is reversed before
 * returning
 */
static struct request *request_splice(struct thread_data *head)
{
	struct request *old;
	struct request *ret;
	struct request *reverse = NULL;

	while (1) {
		old = head->request;
		ret = __sync_val_compare_and_swap(&head->request, old, NULL);
		if (ret == old)
			break;
	}

	while(ret) {
		struct request *tmp = ret;
		ret = ret->next;
		tmp->next = reverse;
		reverse = tmp;
	}
	return reverse;
}

static struct request *allocate_request(void)
{
	struct request *ret = malloc(sizeof(*ret));

	if (!ret) {
		perror("malloc");
		exit(1);
	}

	gettimeofday(&ret->start_time, NULL);
	ret->next = NULL;
	return ret;
}


/*
 * Wake everyone currently waiting on the message list, filling in their
 * thread_data->wake_time with the current time.
 *
 * It's not exactly the current time, it's really the time at the start of
 * the list run.  We want to detect when the scheduler is just preempting the
 * waker and giving away the rest of its timeslice.  So we gtod once at
 * the start of the loop and use that for all the threads we wake.
 *
 * Since pipe mode ends up measuring this other ways, we do the gtod
 * every time in pipe mode
 */
static void xlist_wake_all(struct thread_data *td)
{
	struct thread_data *list;
	struct thread_data *next;
	struct timeval now;

	list = xlist_splice(td);
	gettimeofday(&now, NULL);
	while (list) {
		next = list->next;
		list->next = NULL;
		if (pipe_test) {
			memset(list->pipe_page, 1, pipe_test);
			gettimeofday(&list->wake_time, NULL);
		} else {
			memcpy(&list->wake_time, &now, sizeof(now));
		}
		fpost(&list->futex);
		list = next;
	}
}

/*
 * called by worker threads to send a message and wait for the answer.
 * In reality we're just trading one cacheline with the gtod and futex in
 * it, but that's good enough.  We gtod after waking and use that to
 * record scheduler latency.
 */
static struct request *msg_and_wait(struct thread_data *td)
{
	struct request *req;

	if (pipe_test)
		memset(td->pipe_page, 2, pipe_test);

	/* set ourselves to blocked */
	td->futex = FUTEX_BLOCKED;
	gettimeofday(&td->wake_time, NULL);

	/* add us to the list */
	if (requests_per_sec) {
		td->pending = 0;
		req = request_splice(td);
		if (req) {
			td->futex = FUTEX_RUNNING;
			return req;
		}
	} else {
		xlist_add(td->msg_thread, td);
	}

	fpost(&td->msg_thread->futex);

	/*
	 * don't wait if the main threads are shutting down,
	 * they will never kick us fpost has a full barrier, so as long
	 * as the message thread walks his list after setting stopping,
	 * we shouldn't miss the wakeup
	 */
	if (!stopping) {
		/* if he hasn't already woken us up, wait */
		fwait(&td->futex, NULL);
	}

	return NULL;
}

/*
 * read /proc/stat, return the percentage of non-idle time since
 * the last read.
 */
float read_busy(int fd, char *buf, int len,
		unsigned long long *total_time_ret,
		unsigned long long *idle_time_ret)
{
	unsigned long long total_time = 0;
	unsigned long long idle_time = 0;
	unsigned long long delta;
	unsigned long long delta_idle;
	unsigned long long val;
	int col = 1;
	int ret;
	char *c;
	char *save = NULL;


	ret = lseek(fd, 0, SEEK_SET);
	if (ret < 0) {
		perror("lseek");
		exit(1);
	}
	ret = read(fd, buf, len-1);
	if (ret < 0) {
		perror("failed to read /proc/stat");
		exit(1);
	}
	buf[ret] = '\0';

	/* find the newline */
	c = strchr(buf, '\n');
	if (c == NULL) {
		perror("unable to parse /proc/stat");
		exit(1);
	}
	*c = '\0';

	/* cpu  590315893 45841886 375984879 82585100131 166708940 0 5453892 0 0 0 */
	c = strtok_r(buf, " ", &save);
	if (strcmp(c, "cpu") != 0) {
		perror("unable to parse summary in /proc/stat");
		exit(1);
	}

	while (c != NULL) {
		c = strtok_r(NULL, " ", &save);
		if (!c)
			break;
		val = atoll(c);
		if (col++ == 4)
			idle_time = val;
		total_time += val;
	}

	if (*total_time_ret == 0) {
		*total_time_ret = total_time;
		*idle_time_ret = idle_time;
		return 0.0;
	}

	/* delta is the total time spent doing everything */
	delta = total_time - *total_time_ret;
	delta_idle = idle_time - *idle_time_ret;

	*total_time_ret = total_time;
	*idle_time_ret = idle_time;

	return 100.00 - ((float)delta_idle/(float)delta) * 100.00;
}

#if defined(__x86_64__) || defined(__i386__)
#define nop __asm__ __volatile__("rep;nop": : :"memory")
#elif defined(__aarch64__)
#define nop __asm__ __volatile__("yield" ::: "memory")
#elif defined(__powerpc64__)
#define nop __asm__ __volatile__("nop": : :"memory")
#else
#error Unsupported architecture
#endif

static void usec_spin(unsigned long spin_time)
{
	struct timeval now;
	struct timeval start;
	unsigned long long delta;

	if (spin_time == 0)
		return;

	if (jitter) {
		unsigned int seed = pthread_self();
		unsigned long new_time = rand_r(&seed) % spin_time;
		spin_time = new_time + 1;
	}

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

/*
 * once the message thread starts all his children, this is where he
 * loops until our runtime is up.  Basically this sits around waiting
 * for posting by the worker threads, replying to their messages after
 * a delay of 'sleeptime' + some jitter.
 */
static void run_msg_thread(struct thread_data *td)
{
	unsigned int seed = pthread_self();
	int max_jitter = sleeptime / 4;
	int jitter = 0;

	while (1) {
		td->futex = FUTEX_BLOCKED;
		xlist_wake_all(td);

		if (stopping) {
			xlist_wake_all(td);
			break;
		}
		if (sleeptime)
			fwait(&td->futex, NULL);

		/*
		 * messages shouldn't be instant, sleep a little to make them
		 * wait
		 */
		usec_spin(message_cputime);
		if (!pipe_test && sleeptime) {
			jitter = rand_r(&seed) % max_jitter;
			usleep(sleeptime + jitter);
		}
	}
}

void auto_scale_rps(int *proc_stat_fd,
		    unsigned long long *total_time,
		    unsigned long long *total_idle)
{
	int fd = *proc_stat_fd;
	float busy = 0;
	char proc_stat_buf[512];
	int first_run = 0;
	float delta;
	float target = 1;

	if (fd == -1) {
		fd = open("/proc/stat", O_RDONLY);
		if (fd < 0) {
			perror("unable to open /proc/stat");
			exit(1);
		}
		*proc_stat_fd = fd;
		first_run = 1;
	}
	busy = read_busy(fd, proc_stat_buf, 512, total_time, total_idle);
	if (first_run)
		return;

	if (busy < auto_rps) {
		delta = (float)auto_rps / busy;
		/* delta is > 1 */
		if (delta > 3) {
			delta = 3;
		} else if (delta < 1.2) {
			delta = 1 + (delta - 1) / 8;
		} else if (delta < 1.5) {
			delta = 1 + (delta - 1) / 4;
		}
		target = ceilf((float)requests_per_sec * delta);
		if (target >= (1ULL << 31)) {
			/*
			 * sometimes we don't have enough threads to hit the
			 * target load
			 */
			target = requests_per_sec;
		}
	} else if (busy > auto_rps) {
		/* delta < 1 */
		delta = (float)auto_rps / busy;
		if (delta < 0.3) {
			delta = 0.3;
		} else if (delta > .9) {
			delta += (1 - delta) / 8;
		} else if (delta > .8) {
			delta += (1 - delta) / 4;
		}
		target = floorf((float)requests_per_sec * delta);
		if (target <= 0)
			target = 0;
	} else {
		target = requests_per_sec;
	}
	requests_per_sec = target;
}

/*
 * once the message thread starts all his children, this is where he
 * loops until our runtime is up.  Basically this sits around waiting
 * for posting by the worker threads, replying to their messages after
 * a delay of 'sleeptime' + some jitter.
 */
static void run_rps_thread(struct thread_data *worker_threads_mem)
{
	/* number to wake at a time */
	int nr_to_wake = worker_threads * 2 / 3;
	/* how many times we tried to wake up workers */
	unsigned long total_wake_runs = 0;
	/* list to record tasks waiting for work */
	/* how many times do we need to batch wakeups per second */
	int wakeups_required;
	/* start and end of the thread run */
	struct timeval start;
	struct request *request;

	/* how long do we sleep between wakeup batches */
	unsigned long sleep_time;
	/* total number of times we kicked a worker */
	unsigned long total_wakes = 0;
	int cur_tid = 0;
	int i;

	gettimeofday(&start, NULL);

	while (1) {
		wakeups_required = (requests_per_sec + nr_to_wake - 1) / nr_to_wake;
		sleep_time = USEC_PER_SEC / wakeups_required;

		/* start with a sleep to give everyone the chance to get going */
		usleep(sleep_time);

		gettimeofday(&start, NULL);

		for (i = 0; i < nr_to_wake; i++) {
			struct thread_data *worker;

			worker = worker_threads_mem + cur_tid % worker_threads;
			cur_tid++;

			/* at some point, there's just too much, don't queue more */
			if (worker->pending > 8) {
				continue;
			}
			worker->pending++;
			request = allocate_request();
			request_add(worker, request);
			total_wakes++;
			memcpy(&worker->wake_time, &start, sizeof(start));
			fpost(&worker->futex);
		}
		total_wake_runs++;

		if (stopping) {
			for (i = 0; i < worker_threads; i++)
				fpost(&worker_threads_mem[i].futex);
			break;
		}

	}
	fprintf(stderr, "final rps was %llu\n", requests_per_sec);
}

/*
 * multiply two matrices in a naive way to emulate some cache footprint
 */
static void do_some_math(struct thread_data *thread_data)
{
	unsigned long i, j, k;
	unsigned long *m1, *m2, *m3;

	m1 = &thread_data->data[0];
	m2 = &thread_data->data[matrix_size * matrix_size];
	m3 = &thread_data->data[2 * matrix_size * matrix_size];

	for (i = 0; i < matrix_size; i++) {
		for (j = 0; j < matrix_size; j++) {
			m3[i * matrix_size + j] = 0;

			for (k = 0; k < matrix_size; k++)
				m3[i * matrix_size + j] +=
					m1[i * matrix_size + k] *
					m2[k * matrix_size + j];
		}
	}
}

/*
 * spin or do some matrix arithmetic
 */
static void do_work(struct thread_data *td)
{
	if (matrix_size) {
		unsigned long i;

		for (i = 0; i < operations; i++)
			do_some_math(td);
	} else {
		usec_spin(cputime);
	}
}

/*
 * the worker thread is pretty simple, it just does a single spin and
 * then waits on a message from the message thread
 */
void *worker_thread(void *arg)
{
	struct thread_data *td = arg;
	struct timeval now;
	struct timeval start;
	unsigned long long delta;
	struct request *req = NULL;

	gettimeofday(&start, NULL);
	while(1) {
		if (stopping)
			break;

		req = msg_and_wait(td);
		if (requests_per_sec) {
			while (req) {
				struct request *tmp = req->next;

				do_work(td);

				gettimeofday(&now, NULL);
				delta = tvdelta(&req->start_time, &now);
				td->runtime = tvdelta(&start, &now);
				add_lat(&td->stats, delta);

				free(req);
				req = tmp;
				td->loop_count++;
			}
		} else {
			do_work(td);
			td->loop_count++;
			gettimeofday(&now, NULL);
			td->runtime = tvdelta(&start, &now);
		}

		if (!requests_per_sec) {
			gettimeofday(&now, NULL);
			delta = tvdelta(&td->wake_time, &now);
			if (delta > 0)
				add_lat(&td->stats, delta);
		}
	}
	gettimeofday(&now, NULL);
	td->runtime = tvdelta(&start, &now);

	return NULL;
}

/*
 * the message thread starts his own gaggle of workers and then sits around
 * replying when they post him.  He collects latency stats as all the threads
 * exit
 */
void *message_thread(void *arg)
{
	struct thread_data *td = arg;
	struct thread_data *worker_threads_mem = NULL;
	int i;
	int ret;

	worker_threads_mem = td + 1;

	if (!worker_threads_mem) {
		perror("unable to allocate ram");
		pthread_exit((void *)-ENOMEM);
	}

	for (i = 0; i < worker_threads; i++) {
		pthread_t tid;

		if (matrix_size) {
			worker_threads_mem[i].data = malloc(3 * sizeof(unsigned long) * matrix_size * matrix_size);
			if (!worker_threads_mem[i].data) {
				perror("unable to allocate ram");
				pthread_exit((void *)-ENOMEM);
			}
		}

		worker_threads_mem[i].msg_thread = td;
		ret = pthread_create(&tid, NULL, worker_thread,
				     worker_threads_mem + i);
		if (ret) {
			fprintf(stderr, "error %d from pthread_create\n", ret);
			exit(1);
		}
		worker_threads_mem[i].tid = tid;
	}

	if (requests_per_sec)
		run_rps_thread(worker_threads_mem);
	else
		run_msg_thread(td);

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

static char *units[] = { "B", "KB", "MB", "GB", "TB", "PB", "EB", NULL};

static double pretty_size(double number, char **str)
{
	int divs = 0;

	while(number >= 1024) {
		if (units[divs + 1] == NULL)
			break;
		divs++;
		number /= 1024;
	}
	*str = units[divs];
	return number;
}

static void combine_message_thread_stats(struct stats *stats,
					struct thread_data *thread_data,
					unsigned long long *loop_count,
					unsigned long long *loop_runtime)
{
	struct thread_data *worker;
	int i;
	int msg_i;
	int index = 0;

	*loop_count = 0;
	*loop_runtime = 0;
	for (msg_i = 0; msg_i < message_threads; msg_i++) {
		index++;
		for (i = 0; i < worker_threads; i++) {
			worker = thread_data + index++;
			combine_stats(stats, &worker->stats);
			*loop_count += worker->loop_count;
			*loop_runtime += worker->runtime;
		}
	}
}

static void reset_thread_stats(struct thread_data *thread_data)
{
	struct thread_data *worker;
	int i;
	int msg_i;
	int index = 0;

	for (msg_i = 0; msg_i < message_threads; msg_i++) {
		index++;
		for (i = 0; i < worker_threads; i++) {
			worker = thread_data + index++;
			memset(&worker->stats, 0, sizeof(worker->stats));
		}
	}
}

/* runtime from the command line is in seconds.  Sleep until its up */
static void sleep_for_runtime(struct thread_data *message_threads_mem)
{
	struct timeval now;
	struct timeval zero_time;
	struct timeval last_calc;
	struct timeval start;
	struct stats stats;
	unsigned long long loop_count;
	unsigned long long loop_runtime;
	unsigned long long delta;
	unsigned long long runtime_delta;
	unsigned long long runtime_usec = runtime * USEC_PER_SEC;
	unsigned long long warmup_usec = warmuptime * USEC_PER_SEC;
	unsigned long long interval_usec = intervaltime * USEC_PER_SEC;
	unsigned long long zero_usec = zerotime * USEC_PER_SEC;
	int warmup_done = 0;

	/* if we're autoscaling RPS */
	int proc_stat_fd = -1;
	unsigned long long total_time = 0;
	unsigned long long total_idle = 0;


	memset(&stats, 0, sizeof(stats));
	gettimeofday(&start, NULL);
	last_calc = start;
	zero_time = start;

	while(1) {
		gettimeofday(&now, NULL);
		runtime_delta = tvdelta(&start, &now);

		if (runtime_usec && runtime_delta >= runtime_usec)
			break;

		if (!requests_per_sec && !pipe_test &&
		    runtime_delta > warmup_usec &&
		    !warmup_done && warmuptime) {
			warmup_done = 1;
			fprintf(stderr, "warmup done, zeroing stats\n");
			zero_time = now;
			reset_thread_stats(message_threads_mem);
		} else if (!pipe_test) {
			delta = tvdelta(&last_calc, &now);
			if (delta >= interval_usec) {
				memset(&stats, 0, sizeof(stats));
				combine_message_thread_stats(&stats, message_threads_mem,
					     &loop_count, &loop_runtime);
				show_latencies(&stats, runtime_delta / USEC_PER_SEC);
				last_calc = now;
				if (requests_per_sec) {
					fprintf(stdout, "rps: %.2f\n",
						(double)(loop_count * USEC_PER_SEC) / runtime_delta);
				}
			}
		}
		if (zero_usec) {
			unsigned long long zero_delta;
			zero_delta = tvdelta(&zero_time, &now);
			if (zero_delta > zero_usec) {
				zero_time = now;
				reset_thread_stats(message_threads_mem);
			}
		}
		if (auto_rps)
			auto_scale_rps(&proc_stat_fd, &total_time, &total_idle);
		sleep(1);
	}
	if (proc_stat_fd >= 0)
		close(proc_stat_fd);
	__sync_synchronize();
	stopping = 1;
}


int main(int ac, char **av)
{
	int i;
	int ret;
	struct thread_data *message_threads_mem = NULL;
	struct stats stats;
	double loops_per_sec;
	int p99 = 0;
	int p95 = 0;
	double diff;
	unsigned long long loop_count;
	unsigned long long loop_runtime;

	parse_options(ac, av);

	if (operations)
		matrix_size = sqrt(cache_footprint_kb * 1024 / 3 / sizeof(unsigned long));

again:
	requests_per_sec /= message_threads;
	loops_per_sec = 0;
	stopping = 0;
	memset(&stats, 0, sizeof(stats));

	message_threads_mem = calloc(message_threads * worker_threads + message_threads,
				      sizeof(struct thread_data));


	if (!message_threads_mem) {
		perror("unable to allocate message threads");
		exit(1);
	}

	/* start our message threads, each one starts its own workers */
	for (i = 0; i < message_threads; i++) {
		pthread_t tid;
		int index = i * worker_threads + i;
		ret = pthread_create(&tid, NULL, message_thread,
				     message_threads_mem + index);
		if (ret) {
			fprintf(stderr, "error %d from pthread_create\n", ret);
			exit(1);
		}
		message_threads_mem[index].tid = tid;
	}

	sleep_for_runtime(message_threads_mem);

	for (i = 0; i < message_threads; i++) {
		int index = i * worker_threads + i;
		fpost(&message_threads_mem[index].futex);
		pthread_join(message_threads_mem[index].tid, NULL);
	}
	memset(&stats, 0, sizeof(stats));
	combine_message_thread_stats(&stats, message_threads_mem,
				     &loop_count, &loop_runtime);

	loops_per_sec = loop_count * USEC_PER_SEC;
	loops_per_sec /= loop_runtime;

	free(message_threads_mem);
	calc_p99(&stats, &p95, &p99);

	if (autobench) {
		fprintf(stdout, "cputime %Lu threads %d p99 %d\n",
			cputime, worker_threads, p99);
		if (p99 < 2000) {
			worker_threads++;
			goto again;
		}
		show_latencies(&stats, runtime);
	} else {
		show_latencies(&stats, runtime);
	}

	if (pipe_test) {
		char *pretty;
		double mb_per_sec;
		mb_per_sec = (loop_count * pipe_test * USEC_PER_SEC) / loop_runtime;
		mb_per_sec = pretty_size(mb_per_sec, &pretty);
		printf("avg worker transfer: %.2f ops/sec %.2f%s/s\n",
		       loops_per_sec, mb_per_sec, pretty);

	}
	if (requests_per_sec) {
		diff = (double)p99 / cputime;
		fprintf(stdout, "rps: %.2f p95 (usec) %d p99 (usec) %d p95/cputime %.2f%% p99/cputime %.2f%%\n",
				(double)(loop_count) / runtime, p95, p99, ((double)p95 / cputime) * 100,
				diff * 100);
	}

	return 0;
}