void *
second_thread(void *args)
{
struct second_thread_args *secargs = (struct second_thread_args *)args;
int res;
uint64_t i;
kern_return_t kret;
uint64_t wake_time;
int cpuno;
/* Set scheduling policy */
res = thread_setup(secargs->pol);
if (res != 0) {
printf("Couldn't set thread policy.\n");
exit(1);
}
/*
* Repeatedly pick a random timer length and
* try to sleep exactly that long
*/
for (i = 0; i < secargs->iterations; i++) {
/* Wake up when poked by main thread */
kret = semaphore_wait(secargs->wakeup_semaphore);
if (kret != KERN_SUCCESS) {
errx(1, "semaphore_wait %d", kret);
}
wake_time = mach_absolute_time();
cpuno = cpu_number();
if (wake_time < secargs->last_poke_time) {
/* Woke in past, unsynchronized mach_absolute_time()? */
errx(1, "woke in past %llu (%d) < %llu (%d)", wake_time, cpuno, secargs->last_poke_time, secargs->cpuno);
}
if (cpuno == secargs->cpuno) {
secargs->woke_on_same_cpu++;
}
secargs->wakeup_second_jitter_arr[i] = (double)(wake_time - secargs->last_poke_time);
/* Too much: cut a tracepoint for a debugger */
if (secargs->wakeup_second_jitter_arr[i] >= secargs->too_much) {
kdebug_trace(0xeeeee4 | DBG_FUNC_NONE, 0, 0, 0, 0);
}
kret = semaphore_signal(secargs->return_semaphore);
if (kret != KERN_SUCCESS) {
errx(1, "semaphore_signal %d", kret);
}
}
return NULL;
}
static void loop_kdebug_trace(dt_stat_time_t s) {
do {
dt_stat_token start = dt_stat_time_begin(s);
for (uint32_t i = 0; i<100; i++) {
kdebug_trace(0x97000000 | DBG_FUNC_NONE, i, i, i, i);
kdebug_trace(0x97000000 | DBG_FUNC_NONE, i, i, i, i);
kdebug_trace(0x97000000 | DBG_FUNC_NONE, i, i, i, i);
kdebug_trace(0x97000000 | DBG_FUNC_NONE, i, i, i, i);
kdebug_trace(0x97000000 | DBG_FUNC_NONE, i, i, i, i);
kdebug_trace(0x97000000 | DBG_FUNC_NONE, i, i, i, i);
kdebug_trace(0x97000000 | DBG_FUNC_NONE, i, i, i, i);
kdebug_trace(0x97000000 | DBG_FUNC_NONE, i, i, i, i);
kdebug_trace(0x97000000 | DBG_FUNC_NONE, i, i, i, i);
kdebug_trace(0x97000000 | DBG_FUNC_NONE, i, i, i, i);
}
dt_stat_time_end_batch(s, 1000, start);
} while (!dt_stat_stable(s));
}
int
main(int argc, char **argv)
{
uint64_t iterations, i;
double *jitter_arr, *fraction_arr;
double *wakeup_second_jitter_arr;
uint64_t target_time;
uint64_t sleep_length_abs;
uint64_t min_sleep_ns = 0;
uint64_t max_sleep_ns = DEFAULT_MAX_SLEEP_NS;
uint64_t wake_time;
unsigned random_seed;
boolean_t need_seed = TRUE;
char ch;
int res;
kern_return_t kret;
my_policy_type_t pol;
boolean_t wakeup_second_thread = FALSE;
semaphore_t wakeup_semaphore, return_semaphore;
double avg, stddev, max, min;
double avg_fract, stddev_fract, max_fract, min_fract;
uint64_t too_much;
struct second_thread_args secargs;
pthread_t secthread;
mach_timebase_info(&g_mti);
/* Seed random */
opterr = 0;
while ((ch = getopt(argc, argv, "m:n:hs:w")) != -1 && ch != '?') {
switch (ch) {
case 's':
/* Specified seed for random)() */
random_seed = (unsigned)atoi(optarg);
srandom(random_seed);
need_seed = FALSE;
break;
case 'm':
/* How long per timer? */
max_sleep_ns = strtoull(optarg, NULL, 10);
break;
case 'n':
/* How long per timer? */
min_sleep_ns = strtoull(optarg, NULL, 10);
break;
case 'w':
/* After each timed wait, wakeup another thread */
wakeup_second_thread = TRUE;
break;
case 'h':
print_usage();
exit(0);
break;
default:
fprintf(stderr, "Got unexpected result from getopt().\n");
exit(1);
break;
}
}
argc -= optind;
argv += optind;
if (argc != 3) {
print_usage();
exit(1);
}
if (min_sleep_ns >= max_sleep_ns) {
print_usage();
exit(1);
}
if (need_seed) {
srandom(time(NULL));
}
/* What scheduling policy? */
pol = parse_thread_policy(argv[0]);
/* How many timers? */
iterations = strtoull(argv[1], NULL, 10);
/* How much jitter is so extreme that we should cut a trace point */
too_much = strtoull(argv[2], NULL, 10);
/* Array for data */
jitter_arr = (double*)malloc(sizeof(*jitter_arr) * iterations);
if (jitter_arr == NULL) {
printf("Couldn't allocate array to store results.\n");
exit(1);
}
fraction_arr = (double*)malloc(sizeof(*fraction_arr) * iterations);
if (fraction_arr == NULL) {
printf("Couldn't allocate array to store results.\n");
exit(1);
}
if (wakeup_second_thread) {
/* Array for data */
wakeup_second_jitter_arr = (double*)malloc(sizeof(*jitter_arr) * iterations);
if (wakeup_second_jitter_arr == NULL) {
printf("Couldn't allocate array to store results.\n");
exit(1);
}
kret = semaphore_create(mach_task_self(), &wakeup_semaphore, SYNC_POLICY_FIFO, 0);
if (kret != KERN_SUCCESS) {
printf("Couldn't allocate semaphore %d\n", kret);
exit(1);
}
kret = semaphore_create(mach_task_self(), &return_semaphore, SYNC_POLICY_FIFO, 0);
if (kret != KERN_SUCCESS) {
printf("Couldn't allocate semaphore %d\n", kret);
exit(1);
}
secargs.wakeup_semaphore = wakeup_semaphore;
secargs.return_semaphore = return_semaphore;
secargs.iterations = iterations;
secargs.pol = pol;
secargs.wakeup_second_jitter_arr = wakeup_second_jitter_arr;
secargs.woke_on_same_cpu = 0;
secargs.too_much = too_much;
secargs.last_poke_time = 0ULL;
secargs.cpuno = 0;
res = pthread_create(§hread, NULL, second_thread, &secargs);
if (res) {
err(1, "pthread_create");
}
sleep(1); /* Time for other thread to start up */
}
/* Set scheduling policy */
res = thread_setup(pol);
if (res != 0) {
printf("Couldn't set thread policy.\n");
exit(1);
}
/*
* Repeatedly pick a random timer length and
* try to sleep exactly that long
*/
for (i = 0; i < iterations; i++) {
sleep_length_abs = (uint64_t) (get_random_sleep_length_abs_ns(min_sleep_ns, max_sleep_ns) * (((double)g_mti.denom) / ((double)g_mti.numer)));
target_time = mach_absolute_time() + sleep_length_abs;
/* Sleep */
kret = mach_wait_until(target_time);
wake_time = mach_absolute_time();
jitter_arr[i] = (double)(wake_time - target_time);
fraction_arr[i] = jitter_arr[i] / ((double)sleep_length_abs);
/* Too much: cut a tracepoint for a debugger */
if (jitter_arr[i] >= too_much) {
kdebug_trace(0xeeeee0 | DBG_FUNC_NONE, 0, 0, 0, 0);
}
if (wakeup_second_thread) {
secargs.last_poke_time = mach_absolute_time();
secargs.cpuno = cpu_number();
OSMemoryBarrier();
kret = semaphore_signal(wakeup_semaphore);
if (kret != KERN_SUCCESS) {
errx(1, "semaphore_signal");
}
kret = semaphore_wait(return_semaphore);
if (kret != KERN_SUCCESS) {
errx(1, "semaphore_wait");
}
}
}
/*
* Compute statistics and output results.
*/
compute_stats(jitter_arr, iterations, &avg, &max, &min, &stddev);
compute_stats(fraction_arr, iterations, &avg_fract, &max_fract, &min_fract, &stddev_fract);
putchar('\n');
print_stats_us("jitter", avg, max, min, stddev);
print_stats_fract("%", avg_fract, max_fract, min_fract, stddev_fract);
if (wakeup_second_thread) {
res = pthread_join(secthread, NULL);
if (res) {
err(1, "pthread_join");
}
compute_stats(wakeup_second_jitter_arr, iterations, &avg, &max, &min, &stddev);
putchar('\n');
print_stats_us("second jitter", avg, max, min, stddev);
putchar('\n');
printf("%llu/%llu (%.1f%%) wakeups on same CPU\n", secargs.woke_on_same_cpu, iterations,
100.0*((double)secargs.woke_on_same_cpu)/iterations);
}
return 0;
}
