This is xnu-11215.1.10. See this file in:
/*
* Copyright (c) 2009 Apple Inc. All rights reserved.
*
* @APPLE_OSREFERENCE_LICENSE_HEADER_START@
*
* This file contains Original Code and/or Modifications of Original Code
* as defined in and that are subject to the Apple Public Source License
* Version 2.0 (the 'License'). You may not use this file except in
* compliance with the License. The rights granted to you under the License
* may not be used to create, or enable the creation or redistribution of,
* unlawful or unlicensed copies of an Apple operating system, or to
* circumvent, violate, or enable the circumvention or violation of, any
* terms of an Apple operating system software license agreement.
*
* Please obtain a copy of the License at
* http://www.opensource.apple.com/apsl/ and read it before using this file.
*
* The Original Code and all software distributed under the License are
* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
* Please see the License for the specific language governing rights and
* limitations under the License.
*
* @APPLE_OSREFERENCE_LICENSE_HEADER_END@
*/
#include <unistd.h>
#include <stdio.h>
#include <math.h>
#include <sys/wait.h>
#include <sys/kdebug.h>
#include <sys/types.h>
#include <sys/ptrace.h>
#include <semaphore.h>
#include <stdlib.h>
#include <pthread.h>
#include <fcntl.h>
#include <errno.h>
#include <err.h>
#include <string.h>
#include <libkern/OSAtomic.h>
#include <mach/mach_time.h>
#include <mach/mach.h>
#include <mach/task.h>
#include <mach/semaphore.h>
#include <libproc_internal.h>
#include <os/tsd.h> /* private header for _os_cpu_number */
typedef enum my_policy_type { MY_POLICY_REALTIME, MY_POLICY_TIMESHARE, MY_POLICY_FIXEDPRI } my_policy_type_t;
#define DEFAULT_MAX_SLEEP_NS 2000000000ll /* Two seconds */
#define CONSTRAINT_NANOS (20000000ll) /* 20 ms */
#define COMPUTATION_NANOS (10000000ll) /* 10 ms */
struct mach_timebase_info g_mti;
#define assert(truth, label) do { if(!(truth)) { printf("Thread %p: failure on line %d\n", pthread_self(), __LINE__); goto label; } } while (0)
struct second_thread_args {
semaphore_t wakeup_semaphore;
semaphore_t return_semaphore;
uint64_t iterations;
my_policy_type_t pol;
double *wakeup_second_jitter_arr;
uint64_t woke_on_same_cpu;
uint64_t too_much;
volatile uint64_t last_poke_time;
volatile int cpuno;
};
void *
second_thread(void *args);
void
print_usage()
{
printf("Usage: jitter [-w] [-s <random seed>] [-n <min sleep, ns>] [-m <max sleep, ns>] <realtime | timeshare | fixed> <num iterations> <traceworthy jitter, ns>\n");
}
my_policy_type_t
parse_thread_policy(const char *str)
{
if (strcmp(str, "timeshare") == 0) {
return MY_POLICY_TIMESHARE;
} else if (strcmp(str, "realtime") == 0) {
return MY_POLICY_REALTIME;
} else if (strcmp(str, "fixed") == 0) {
return MY_POLICY_FIXEDPRI;
} else {
printf("Invalid thread policy %s\n", str);
exit(1);
}
}
int
thread_setup(my_policy_type_t pol)
{
int res;
switch (pol) {
case MY_POLICY_TIMESHARE:
{
return 0;
}
case MY_POLICY_REALTIME:
{
thread_time_constraint_policy_data_t pol;
/* Hard-coded realtime parameters (similar to what Digi uses) */
pol.period = 100000;
pol.constraint = CONSTRAINT_NANOS * g_mti.denom / g_mti.numer;
pol.computation = COMPUTATION_NANOS * g_mti.denom / g_mti.numer;
pol.preemptible = 0; /* Ignored by OS */
res = thread_policy_set(mach_thread_self(), THREAD_TIME_CONSTRAINT_POLICY, (thread_policy_t) &pol, THREAD_TIME_CONSTRAINT_POLICY_COUNT);
assert(res == 0, fail);
break;
}
case MY_POLICY_FIXEDPRI:
{
thread_extended_policy_data_t pol;
pol.timeshare = 0;
res = thread_policy_set(mach_thread_self(), THREAD_EXTENDED_POLICY, (thread_policy_t) &pol, THREAD_EXTENDED_POLICY_COUNT);
assert(res == 0, fail);
break;
}
default:
{
printf("invalid policy type\n");
return 1;
}
}
return 0;
fail:
return 1;
}
uint64_t
get_random_sleep_length_abs_ns(uint64_t min_sleep_ns, uint64_t max_sleep_ns)
{
uint64_t tmp;
tmp = (uint32_t)random();
tmp <<= 32;
tmp |= (uint32_t)random();
/* Now use the random number to sleep amount within the window */
tmp %= (max_sleep_ns - min_sleep_ns);
return min_sleep_ns + tmp;
}
void
compute_stats(double *values, uint64_t count, double *average_magnitudep, double *maxp, double *minp, double *stddevp)
{
uint64_t i;
double _sum = 0;
double _max = 0;
double _min = (double)INT64_MAX;
double _avg = 0;
double _dev = 0;
for (i = 0; i < count; i++) {
_sum += fabs(values[i]);
_max = values[i] > _max ? values[i] : _max;
_min = values[i] < _min ? values[i] : _min;
}
_avg = _sum / (double)count;
_dev = 0;
for (i = 0; i < count; i++) {
_dev += pow((values[i] - _avg), 2);
}
_dev /= count;
_dev = sqrt(_dev);
*average_magnitudep = _avg;
*maxp = _max;
*minp = _min;
*stddevp = _dev;
}
void
print_stats_us(const char *label, double avg, double max, double min, double stddev)
{
printf("Max %s: %.1lfus\n", label, max / 1000.0 * (((double)g_mti.numer) / ((double)g_mti.denom)));
printf("Min %s: %.1lfus\n", label, min / 1000.0 * (((double)g_mti.numer) / ((double)g_mti.denom)));
printf("Avg magnitude of %s: %.1lfus\n", label, avg / 1000.0 * (((double)g_mti.numer) / ((double)g_mti.denom)));
printf("Stddev: %.1lfus\n", stddev / 1000.0 * (((double)g_mti.numer) / ((double)g_mti.denom)));
putchar('\n');
}
void
print_stats_fract(const char *label, double avg, double max, double min, double stddev)
{
printf("Max %s jitter: %.1lf%%\n", label, max * 100);
printf("Min %s jitter: %.1lf%%\n", label, min * 100);
printf("Avg %s jitter: %.1lf%%\n", label, avg * 100);
printf("Stddev: %.1lf%%\n", stddev * 100);
putchar('\n');
}
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);
}
/*
* Disable the wake monitor. If we are
* performing a large number of
* iterations, the wake monitor may
* cause this process to get suspended,
* thus causing a large jitter value.
*/
if (proc_disable_wakemon(getpid()) != KERN_SUCCESS) {
printf("Couldn't disable wake monitor.\n");
/* For now, do not exit; this call could be locked down */
}
/*
* 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 = _os_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;
}
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 = _os_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;
}