tools/tests/jitter/timer_jitter.c

   1 /*
   2  * Copyright (c) 2009 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 #include <unistd.h>
  29 #include <stdio.h>
  30 #include <math.h>
  31 #include <sys/wait.h>
  32 #include <sys/syscall.h>
  33 #include <sys/types.h>
  34 #include <sys/ptrace.h>
  35 #include <semaphore.h>
  36 #include <stdlib.h>
  37 #include <pthread.h>
  38 #include <fcntl.h>
  39 #include <errno.h>
  40 #include <err.h>
  41 #include <string.h>
  42
  43 #include <libkern/OSAtomic.h>
  44
  45 #include <mach/mach_time.h>
  46 #include <mach/mach.h>
  47 #include <mach/task.h>
  48 #include <mach/semaphore.h>
  49
  50 typedef enum my_policy_type { MY_POLICY_REALTIME, MY_POLICY_TIMESHARE, MY_POLICY_FIXEDPRI } my_policy_type_t;
  51
  52 #define DEFAULT_MAX_SLEEP_NS    2000000000ll /* Two seconds */
  53 #define CONSTRAINT_NANOS        (20000000ll)    /* 20 ms */
  54 #define COMPUTATION_NANOS       (10000000ll)    /* 10 ms */
  55
  56 struct mach_timebase_info g_mti;
  57
  58 #define assert(truth, label) do { if(!(truth)) { printf("Thread %p: failure on line %d\n", pthread_self(), __LINE__); goto label; } } while (0)
  59
  60 struct second_thread_args {
  61         semaphore_t wakeup_semaphore;
  62         semaphore_t return_semaphore;
  63         uint64_t iterations;
  64         my_policy_type_t pol;
  65         double *wakeup_second_jitter_arr;
  66         uint64_t woke_on_same_cpu;
  67         uint64_t too_much;
  68         volatile uint64_t last_poke_time;
  69         volatile int cpuno;
  70 };
  71
  72 extern int cpu_number(void);
  73
  74 void *
  75 second_thread(void *args);
  76
  77 void
  78 print_usage()
  79 {
  80         printf("Usage: jitter [-w] [-s <random seed>] [-n <min sleep, ns>] [-m <max sleep, ns>] <realtime | timeshare | fixed> <num iterations> <traceworthy jitter, ns>\n");
  81 }
  82
  83 my_policy_type_t
  84 parse_thread_policy(const char *str)
  85 {
  86         if (strcmp(str, "timeshare") == 0) {
  87                 return MY_POLICY_TIMESHARE;
  88         } else if (strcmp(str, "realtime") == 0) {
  89                 return MY_POLICY_REALTIME;
  90         } else if (strcmp(str, "fixed") == 0) {
  91                 return MY_POLICY_FIXEDPRI;
  92         } else {
  93                 printf("Invalid thread policy %s\n", str);
  94                 exit(1);
  95         }
  96 }
  97
  98 int
  99 thread_setup(my_policy_type_t pol)
 100 {
 101         int res;
 102
 103         switch (pol) {
 104                 case MY_POLICY_TIMESHARE:
 105                 {
 106                         return 0;
 107                 }
 108                 case MY_POLICY_REALTIME:
 109                 {
 110                         thread_time_constraint_policy_data_t pol;
 111
 112                         /* Hard-coded realtime parameters (similar to what Digi uses) */
 113                         pol.period = 100000;
 114                         pol.constraint =  CONSTRAINT_NANOS * g_mti.denom / g_mti.numer;
 115                         pol.computation = COMPUTATION_NANOS * g_mti.denom / g_mti.numer;
 116                         pol.preemptible = 0; /* Ignored by OS */
 117
 118                         res = thread_policy_set(mach_thread_self(), THREAD_TIME_CONSTRAINT_POLICY, (thread_policy_t) &pol, THREAD_TIME_CONSTRAINT_POLICY_COUNT);
 119                         assert(res == 0, fail);
 120                         break;
 121                 }
 122                 case MY_POLICY_FIXEDPRI:
 123                 {
 124                         thread_extended_policy_data_t pol;
 125                         pol.timeshare = 0;
 126
 127                         res = thread_policy_set(mach_thread_self(), THREAD_EXTENDED_POLICY, (thread_policy_t) &pol, THREAD_EXTENDED_POLICY_COUNT);
 128                         assert(res == 0, fail);
 129                         break;
 130                 }
 131                 default:
 132                 {
 133                         printf("invalid policy type\n");
 134                         return 1;
 135                 }
 136         }
 137
 138         return 0;
 139 fail:
 140         return 1;
 141 }
 142
 143 uint64_t
 144 get_random_sleep_length_abs_ns(uint64_t min_sleep_ns, uint64_t max_sleep_ns)
 145 {
 146         uint64_t tmp;
 147
 148         tmp = (uint32_t)random();
 149         tmp <<= 32;
 150         tmp |= (uint32_t)random();
 151
 152         /* Now use the random number to sleep amount within the window */
 153         tmp %= (max_sleep_ns - min_sleep_ns);
 154
 155         return min_sleep_ns + tmp;
 156 }
 157
 158 void
 159 compute_stats(double *values, uint64_t count, double *average_magnitudep, double *maxp, double *minp, double *stddevp)
 160 {
 161         uint64_t i;
 162         double _sum = 0;
 163         double _max = 0;
 164         double _min = (double)INT64_MAX;
 165         double _avg = 0;
 166         double _dev = 0;
 167
 168         for (i = 0; i < count; i++) {
 169                 _sum += fabs(values[i]);
 170                 _max = values[i] > _max ? values[i] : _max;
 171                 _min = values[i] < _min ? values[i] : _min;
 172         }
 173
 174         _avg = _sum / (double)count;
 175
 176         _dev = 0;
 177         for (i = 0; i < count; i++) {
 178                 _dev += pow((values[i] - _avg), 2);
 179         }
 180
 181         _dev /= count;
 182         _dev = sqrt(_dev);
 183
 184         *average_magnitudep = _avg;
 185         *maxp = _max;
 186         *minp = _min;
 187         *stddevp = _dev;
 188 }
 189
 190 void
 191 print_stats_us(const char *label, double avg, double max, double min, double stddev)
 192 {
 193         printf("Max %s: %.1lfus\n", label, max / 1000.0 * (((double)g_mti.numer) / ((double)g_mti.denom)));
 194         printf("Min %s: %.1lfus\n", label, min / 1000.0 * (((double)g_mti.numer) / ((double)g_mti.denom)));
 195         printf("Avg magnitude of %s: %.1lfus\n", label, avg / 1000.0 * (((double)g_mti.numer) / ((double)g_mti.denom)));
 196         printf("Stddev: %.1lfus\n", stddev / 1000.0 * (((double)g_mti.numer) / ((double)g_mti.denom)));
 197         putchar('\n');
 198 }
 199
 200 void
 201 print_stats_fract(const char *label, double avg, double max, double min, double stddev)
 202 {
 203         printf("Max %s jitter: %.1lf%%\n", label, max * 100);
 204         printf("Min %s jitter: %.1lf%%\n", label, min * 100);
 205         printf("Avg %s jitter: %.1lf%%\n", label, avg * 100);
 206         printf("Stddev: %.1lf%%\n", stddev * 100);
 207         putchar('\n');
 208 }
 209
 210 int
 211 main(int argc, char **argv)
 212 {
 213         uint64_t iterations, i;
 214         double *jitter_arr, *fraction_arr;
 215         double *wakeup_second_jitter_arr;
 216         uint64_t target_time;
 217         uint64_t sleep_length_abs;
 218         uint64_t min_sleep_ns = 0;
 219         uint64_t max_sleep_ns = DEFAULT_MAX_SLEEP_NS;
 220         uint64_t wake_time;
 221         unsigned random_seed;
 222         boolean_t need_seed = TRUE;
 223         char ch;
 224         int res;
 225         kern_return_t kret;
 226         my_policy_type_t pol;
 227         boolean_t wakeup_second_thread = FALSE;
 228         semaphore_t wakeup_semaphore, return_semaphore;
 229
 230         double avg, stddev, max, min;
 231         double avg_fract, stddev_fract, max_fract, min_fract;
 232         uint64_t too_much;
 233
 234         struct second_thread_args secargs;
 235         pthread_t secthread;
 236
 237         mach_timebase_info(&g_mti);
 238
 239         /* Seed random */
 240         opterr = 0;
 241         while ((ch = getopt(argc, argv, "m:n:hs:w")) != -1 && ch != '?') {
 242                 switch (ch) {
 243                         case 's':
 244                                 /* Specified seed for random)() */
 245                                 random_seed = (unsigned)atoi(optarg);
 246                                 srandom(random_seed);
 247                                 need_seed = FALSE;
 248                                 break;
 249                         case 'm':
 250                                 /* How long per timer? */
 251                                 max_sleep_ns = strtoull(optarg, NULL, 10);
 252                                 break;
 253                         case 'n':
 254                                 /* How long per timer? */
 255                                 min_sleep_ns = strtoull(optarg, NULL, 10);
 256                                 break;
 257                         case 'w':
 258                                 /* After each timed wait, wakeup another thread */
 259                                 wakeup_second_thread = TRUE;
 260                                 break;
 261                         case 'h':
 262                                 print_usage();
 263                                 exit(0);
 264                                 break;
 265                         default:
 266                                 fprintf(stderr, "Got unexpected result from getopt().\n");
 267                                 exit(1);
 268                                 break;
 269                 }
 270         }
 271
 272         argc -= optind;
 273         argv += optind;
 274
 275         if (argc != 3) {
 276                 print_usage();
 277                 exit(1);
 278         }
 279
 280         if (min_sleep_ns >= max_sleep_ns) {
 281                 print_usage();
 282                 exit(1);
 283         }
 284
 285         if (need_seed) {
 286                 srandom(time(NULL));
 287         }
 288
 289         /* What scheduling policy? */
 290         pol = parse_thread_policy(argv[0]);
 291
 292         /* How many timers? */
 293         iterations = strtoull(argv[1], NULL, 10);
 294
 295         /* How much jitter is so extreme that we should cut a trace point */
 296         too_much = strtoull(argv[2], NULL, 10);
 297
 298         /* Array for data */
 299         jitter_arr = (double*)malloc(sizeof(*jitter_arr) * iterations);
 300         if (jitter_arr == NULL) {
 301                 printf("Couldn't allocate array to store results.\n");
 302                 exit(1);
 303         }
 304
 305         fraction_arr = (double*)malloc(sizeof(*fraction_arr) * iterations);
 306         if (fraction_arr == NULL) {
 307                 printf("Couldn't allocate array to store results.\n");
 308                 exit(1);
 309         }
 310
 311         if (wakeup_second_thread) {
 312                 /* Array for data */
 313                 wakeup_second_jitter_arr = (double*)malloc(sizeof(*jitter_arr) * iterations);
 314                 if (wakeup_second_jitter_arr == NULL) {
 315                         printf("Couldn't allocate array to store results.\n");
 316                         exit(1);
 317                 }
 318
 319                 kret = semaphore_create(mach_task_self(), &wakeup_semaphore, SYNC_POLICY_FIFO, 0);
 320                 if (kret != KERN_SUCCESS) {
 321                         printf("Couldn't allocate semaphore %d\n", kret);
 322                         exit(1);
 323                 }
 324
 325                 kret = semaphore_create(mach_task_self(), &return_semaphore, SYNC_POLICY_FIFO, 0);
 326                 if (kret != KERN_SUCCESS) {
 327                         printf("Couldn't allocate semaphore %d\n", kret);
 328                         exit(1);
 329                 }
 330
 331
 332                 secargs.wakeup_semaphore = wakeup_semaphore;
 333                 secargs.return_semaphore = return_semaphore;
 334                 secargs.iterations = iterations;
 335                 secargs.pol = pol;
 336                 secargs.wakeup_second_jitter_arr = wakeup_second_jitter_arr;
 337                 secargs.woke_on_same_cpu = 0;
 338                 secargs.too_much = too_much;
 339                 secargs.last_poke_time = 0ULL;
 340                 secargs.cpuno = 0;
 341
 342                 res = pthread_create(&secthread, NULL, second_thread, &secargs);
 343                 if (res) {
 344                         err(1, "pthread_create");
 345                 }
 346
 347                 sleep(1); /* Time for other thread to start up */
 348         }
 349
 350         /* Set scheduling policy */
 351         res = thread_setup(pol);
 352         if (res != 0) {
 353                 printf("Couldn't set thread policy.\n");
 354                 exit(1);
 355         }
 356
 357         /*
 358          * Repeatedly pick a random timer length and
 359          * try to sleep exactly that long
 360          */
 361         for (i = 0; i < iterations; i++) {
 362                 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)));
 363                 target_time = mach_absolute_time() + sleep_length_abs;
 364
 365                 /* Sleep */
 366                 kret = mach_wait_until(target_time);
 367                 wake_time = mach_absolute_time();
 368
 369                 jitter_arr[i] = (double)(wake_time - target_time);
 370                 fraction_arr[i] = jitter_arr[i] / ((double)sleep_length_abs);
 371
 372                 /* Too much: cut a tracepoint for a debugger */
 373                 if (jitter_arr[i] >= too_much) {
 374                         syscall(SYS_kdebug_trace, 0xeeeeeeee, 0, 0, 0, 0);
 375                 }
 376
 377                 if (wakeup_second_thread) {
 378                         secargs.last_poke_time = mach_absolute_time();
 379                         secargs.cpuno = cpu_number();
 380                         OSMemoryBarrier();
 381                         kret = semaphore_signal(wakeup_semaphore);
 382                         if (kret != KERN_SUCCESS) {
 383                                 errx(1, "semaphore_signal");
 384                         }
 385
 386                         kret = semaphore_wait(return_semaphore);
 387                         if (kret != KERN_SUCCESS) {
 388                                 errx(1, "semaphore_wait");
 389                         }
 390
 391                 }
 392         }
 393
 394         /*
 395          * Compute statistics and output results.
 396          */
 397         compute_stats(jitter_arr, iterations, &avg, &max, &min, &stddev);
 398         compute_stats(fraction_arr, iterations, &avg_fract, &max_fract, &min_fract, &stddev_fract);
 399
 400         putchar('\n');
 401         print_stats_us("jitter", avg, max, min, stddev);
 402         print_stats_fract("%", avg_fract, max_fract, min_fract, stddev_fract);
 403
 404         if (wakeup_second_thread) {
 405
 406                 res = pthread_join(secthread, NULL);
 407                 if (res) {
 408                         err(1, "pthread_join");
 409                 }
 410
 411                 compute_stats(wakeup_second_jitter_arr, iterations, &avg, &max, &min, &stddev);
 412
 413                 putchar('\n');
 414                 print_stats_us("second jitter", avg, max, min, stddev);
 415
 416                 putchar('\n');
 417                 printf("%llu/%llu (%.1f%%) wakeups on same CPU\n", secargs.woke_on_same_cpu, iterations,
 418                            100.0*((double)secargs.woke_on_same_cpu)/iterations);
 419         }
 420
 421         return 0;
 422 }
 423
 424 void *
 425 second_thread(void *args)
 426 {
 427         struct second_thread_args *secargs = (struct second_thread_args *)args;
 428         int res;
 429         uint64_t i;
 430         kern_return_t kret;
 431         uint64_t wake_time;
 432         int cpuno;
 433
 434         /* Set scheduling policy */
 435         res = thread_setup(secargs->pol);
 436         if (res != 0) {
 437                 printf("Couldn't set thread policy.\n");
 438                 exit(1);
 439         }
 440
 441         /*
 442          * Repeatedly pick a random timer length and
 443          * try to sleep exactly that long
 444          */
 445         for (i = 0; i < secargs->iterations; i++) {
 446
 447                 /* Wake up when poked by main thread */
 448                 kret = semaphore_wait(secargs->wakeup_semaphore);
 449                 if (kret != KERN_SUCCESS) {
 450                         errx(1, "semaphore_wait %d", kret);
 451                 }
 452
 453                 wake_time = mach_absolute_time();
 454                 cpuno = cpu_number();
 455                 if (wake_time < secargs->last_poke_time) {
 456                         /* Woke in past, unsynchronized mach_absolute_time()? */
 457
 458                         errx(1, "woke in past %llu (%d) < %llu (%d)", wake_time, cpuno, secargs->last_poke_time, secargs->cpuno);
 459                 }
 460
 461                 if (cpuno == secargs->cpuno) {
 462                         secargs->woke_on_same_cpu++;
 463                 }
 464
 465                 secargs->wakeup_second_jitter_arr[i] = (double)(wake_time - secargs->last_poke_time);
 466
 467                 /* Too much: cut a tracepoint for a debugger */
 468                 if (secargs->wakeup_second_jitter_arr[i] >= secargs->too_much) {
 469                         syscall(SYS_kdebug_trace, 0xeeeeeeef, 0, 0, 0, 0);
 470                 }
 471
 472                 kret = semaphore_signal(secargs->return_semaphore);
 473                 if (kret != KERN_SUCCESS) {
 474                         errx(1, "semaphore_signal %d", kret);
 475                 }
 476
 477         }
 478
 479         return NULL;
 480 }